Rake angle and grip

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Mark Pierpoint
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Re: Rake angle and grip

Post by Mark Pierpoint »

A good Passenger normally helps it turn better :-D
.HOWAY THE LADS. THE MORE THE MERRIER
Taffy
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Re: Rake angle and grip

Post by Taffy »

we measured Aled's trail last weekend. it was really technical and cost us oh so much money!!!!

luckily the outfit was standing parallel to the workshop bench.
we pulled the front brake on and held it there with a tie-wrap
we found an old nylon chain roller and placed it under the middle of the front tyre
we measured the distance across from the spine just behind the headstock to the bench
i held the sidecar wheel up to stop any friction
we turned the steering to right lock
the outfit moved closer to the bench - so we have trail for sure
we then moved the chain roller forwards "X"mm under the tyre forwards of cente
we then turned the steering to right lock again and...
the outfit's spine never moved
we used a plumbob dangling from the wheel spindle and marked the workshop underneath it
I marked out from the nylon spacer. this is the point of zero trail
I measured back from this mark to the plumbob mark
we now know the trail.

very simple and easy way to find it. this figure will change between 21" and 20" wheels.

Taffy
Last edited by Taffy on Wed Sep 17, 2014 12:10 am, edited 1 time in total.
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Doogle
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Re: Rake angle and grip

Post by Doogle »

This thread is perfect for a cancelled meeting day...Just killed an hour.
The only reply I understood was Pingpongs.....
Peter Glazier
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Re: Rake angle and grip

Post by Peter Glazier »

Taffy, if you ever get the chance to meet Mike Guildford (Martin's dad) I'm sure you would have a very interesting conversation. Mike, of course, had a big design input with the early Wasps, and continued to have an influence on sidecarcross design for many years. I would credit Mike with the modern outfits we have today. In the early eighties, many were experimenting with lightweights, but, while most (me included) were following Wasp geometry, it was Mike who brought the centre of gravity forward, used a long rear swinging arm, and introduced water cooling to what at the time were air cooled engines on the outfit he built for Nigel Pinchbeck and Martin to race, very successfully.
I believe Mike is into the vintage tractor scene these days, but it would be lovely to see him at a meeting again one day.
Taffy
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Re: Rake angle and grip

Post by Taffy »

without a doubt this little cash strapped nation certainly gets some good ideas. rumour has it that KHR has done a chassis that helps a rider find it easier to steer. two things come to mind: steeper rake or zero trail... or...put the two together.

in the future I can see the rider going forwards, the engine will go back and they will use solo swing arms again. if a rider weighs 100KG and moves forwards 2" a 33KG engine can move back 6" for the same balance. if you take into account the airbox blah blah and other crap let's settle for half that, so 3". back to solo swingarms and a weight saving of 7+ kilos.

sidecars need lots of BHP - like 65-90bhp so the longer the swing arm the less rear squat and anti-squat you get but at three times the swing arm weight?????????? the engine mounts at the front will then become ULTRA critical for the correct squat - or neutral feeling whatever.

I've done loads of solo work with anti squat. one day I lifted the front of the engine 10mm and took it easy for three bends first time out on an MX track - how hard can it be right?

gave it the berries coming out of the 4th and shot straight onto the inside grass and went under the rope.... the back had gone straight down the front went light, I'm still cranked over and went onto that bit of inside grass that nobody ever uses. phonominal. on a solo it happens at 45 degrees on a sidecar it is always vertical.

a C of G that keeps going up and down though slows a team up as it changes based on the 'hard use - or not so' of the throttle at any given corner. hairpins are a nightmare, long corners not at all so a longer swing arm stops this or makes it easier.

think of a man lifting a table. if he has a short arm he lifts one corner = easy and the table flies up at one end, if he has a long arm his hand is now under the middle of the table and he can't lift it (his arm got longer weakening him and now he is picking up more of the table). that is part of the reason you have very long swing arms in ScX I guess.

but you can get it right with a shorter arm and the 1/3rd weight I'd have thought was better? unsprung weight saved is GOLD.

here is a standard and an exagarated view. the rider and passenger have gone foot forwards and the engine has gone backwards the same. the truth is more subtle....
Image
becomes
Image

if the headstock goes forwards so do the front radiator bars (sorry, don't know their name?) and a lanky rider can attack lefts far better and the passenger moves up. more wight on the front = more grip.

if the front rad bars goes forwards then the sidecar swing arm pivot can go forwards creating a longer arm without moving the wheel. (this is what I meant Sean M) a longer arm is, I hope, desirable in the chair as it can't cope with big bumps which are currently slewing the outfits hard left.

the chair would need a stronger shock though and that means on lefts the chair won't sink as much when the passenger moves outside the chair. a good thing? or a bad thing? or will that stronger shock stand up to straightline fast bumps and landings that much better.

In a solo we look for "balance" in the shocks, when things are nice you can jump up and down and both ends are in rythem. however,as has been mentioned before, a sidecar isn't in balance. a monster shock on the rear, two mediums on the front and a light one in the chair. not really harmonious.

but maybe a shorter rear SA (lighter rear shock) and a longer one in the chair would bring dividends and a feeling of being 'planted'.

one other benefit of steeper rake is that the bikes can broadside easier like a speedway bike and I see Willemsen gets quite cocky sometimes at that kind of thing - he has every right -but the headstock angle is truly part of that.

Taffy
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Re: Rake angle and grip

Post by Taffy »

I thought I'd get this done now. NOT the right timing you'd think but with two GPs and a British round to go it is time to reflect on what changes the leading riders might order in their new chassis and what most of you might try to change to your older ones to keep up!

firstly, can I thank the riders both now and retired, that gave me worldly advice to put me in the picture. so to those of you that put me right...thanks - you know who you are! a few things have come up in the year since I started this subject and todays subjects are
ELECTRIC POWER STEERING!!!!!
RUNNING WITH MORE TRAIL
CAMBER


ELECTRIC POWER STEERING!!!!!
as said before: the RULES HAVE CHANGED. with Lithium Ion batteries weighing ONE FIFTH of a gel cel there is room for batteries everywhere and anywhere.

how about some TRAIL?
most riders run little or no trail on the outfit. some of you have run with the front arm in the rear bolt hole not just on sand but have had cause to regret running with it in the back hole on loam soil as well. the outfit has turned on a sixpence - brilliant - fantastic! alas the outfit is susceptable to violent wobbles from SLIDING INTO BUMPS, NOT SO MUCH OVER THEM BUT FROM THE SIDE ETC.

here is a diagram of why this happens?
this is how you are running
Image
as the outfit slides, a whallop below the spindle is like kicking the unicyclists wheel at the lowest point. it doesn't deflect him it just 'shunts' the whole bike.

if you ran with lots of trail
Image
try that kick now in the middle at the blue dot and the steering will flick. you have to kick the wheel at the sky blue dot to have no effect.


well here is a video of EPS
here is an electric power steering unit. right click on the hyperlink and open it in e new screen.
https://www.youtube.com/watch?v=HsWhxzfRRSc
this EPS is just one of a few that the quad world has brough out over the past 3-5 years. there are several to choose from and all look pretty light.

could this be what you are looking for? unlike solos that need new triple clamps just to experiment. all you need is to put the front arm in the rear hole, fit EPS and see how it goes.
if the EPS appears damped with little deflection through the quad rider's hands. after all, what is the point in EPS if you have light steering but fracture your wrists when you come to the first rock - right?

throw away the steering damper!

now this would be an experiment. let's say the back hole is 15mm away right? then if it works you have shortened the wheelbase and put more weight on the front but the bike is quicker. what you wanted was the same wheelbase and the shocks to be 'as before'. so you have to consider the headstock moving forwards on the new chassis by 15mm and then the wheel is back in the same place - right?

MY OWN TESTS ON A SOLO OF STEEPER HEAD ANGLE
Image
the above photo is from my workshops of the steering head of my Husaberg. I welded another headstock on the front and converted the old one onto a fuel cap and the spine of the frame now holds 3 litres of fuel.

i have changed the headstock angle from 28.5 degrees to 23.5 degrees. :dontknow:
the headstock rotated forward 78mm around and over and around the front wheel spindle for the 5 degree change - measured at the top edge of the steering head. meanwhile the point on the ground went BACK the other way 14mm. so my trail was reduced by 14mm.
with the trail reduced as a result, I then moved the headstock forwards again on paper at the same new angle the 14mm on top of the 78mm to get the right trail again and back to 'aswas'. so the headstock had gone around 92mm to here.

at this point I have the same trail as before. little trail is very light to steer, you have to turn the steering a lot to change direction but it is light. with the new headstock angle it has become extremely light to steer. read on but remember that it is expected to be superlight, like FEATHERLIGHT.

so then, because it was going to be far easier and lighter to steer I decided to increase the trail, this makes the steering slightly heavier (so back to aswas) but the bike will flick on its side at the touch of the bars. I estimated that it would need about 8mm less offset at the clamps to get this trail, the trail where the bars roll into a corner nicely, this is a feeling any solo rider knows well... as you arrive at a corner, slowing and braking the bike turns in nicely. I knew that the 22mm off set clamps would become around 14mm offset, this would reduce the wheelbase as well by 8mm and I didn't want that. Now I wasn't sure that it would be 14mm, i figured it was between 11mm-14mm so i added ANOTHER 8mm to the headstock making 100mm in total. this was in ANTICIPATION.

off came the 22mm offset clamps for a set of 14mm offset. these are the least offset that KTM make. these were nearly right but the steering pointed ahead slightly instead of "flopping in" as the corner tightened. something a solo rider takes for granted and feels right. so I had eccentric bushes put into another set and they are now 12mm offset. the bars now "roll in" turn more the tighter the bend. perfect!

the bike handles perfecly and is like a bicycle to ride, it has the same headstock angle - like a speedway bike! but it has lots of trail so my party tricks are to ride no hands and slap the bars or to ride up to say a roundabout at 1mph still wiggling and balancing without footing. over rocks and stuff it is like I'm on a 125. the wheelbase has been altered by 1mm.

back to sidecarX but I thought I'd let you know.

if you were to run with trail (and we are working on the basis that you run none or very little) I say IF,,,,then you get a natural damping effect in the steering that aids front wheel grip. have you ever ridden a trials bike? when you go to full lock and open the throttle, the power drives straight through the sideways facing front wheel 'ploughing on'. trials bikes have very little trail. there is therefore no damping of the drive at the front wheel and steering is lost in 'understeer'.

just a reminder, look again at the diagram below and the left illustration. that is yours...
Image


below (the third illustration from above), you can see that with trail, you get a natural damping and the hysterisis of the tyre and its grip recover. the rear wheel drives ahead of the steering trying to straighten the bike up. but as you hit bumps there is more 'give'. you need EPS to do this.
Image

CAMBER
It was said to me that the reason outfits have a lot of Rake (known in the car world as Castor) is because when the steering is turned the steering has lots of camber as well and that the amount of camber they have is good for them?

camber is how much a tyre leans to the side when seen from infront of the tyre. so from the front when steering ahead it's zero but it is positive camber on either lock. in the photo below the wheel is turned right and falling to the right:
Image

if the steering was upright we know that the wheel is upright so there is zero degrees of camber. if the wheel was turned exactly 90d to the right we know it would have the same camber as the rake so say 26-30d perhaps?
the steering looks like it is at 45d which is halfway so shall we say it has 13-14d of camber at this moment?

does it really need that much? no, as you can see, a geat deal of the tyre is not working, certainly the outfit has gone into understeer. the greater the angle of camber the more the tyre jumps from the top of one bump to recover a long way away at 14 degrees, so far infact that it collapses again - after all you only have one steering tyre and a thin one at that and this is understeer.

the more upright the steering the smaller the distance the wheel travels sideways to recover. so look at the diagram below and at the right hand half. if the tyre were more upright it can recover more quickly.
Image
on the left is oversteer or opposite lock and drifting as you might say.
on the right is normal understeer when cornering. note the middle tyre trying to grip on the downward slope while sliding. here, the more vertical the steering the more the tyre would recover on the 'far side' of a bump.

also with camber like this it is OK when in understeer but in oversteer (drifting on opposite lock) the tyre can't grip and falls away. a steeper rake would make BOTH the halves above nearer to each other for a more consistant performance between over and understeer.

a more upright steering/front wheel and another ply in the front tyre?

look at the outfit behind and IF it had been on the lock of the front one THAT is more like the camber needed. the answer is therefore less rake and thus less camber at extreme lock.

so where does all this leave you?
you need less rake with a more upright headstock - this in itself is nothing
you need the headstock therefore forwards 60mm - 80mm etc? - this in itself is nothing
but getting the rider's weight further forwards WILL make a difference and it will be massive

having less camber at extreme lock will give MORE GRIP

with the handlebars set 60-80mm further forwards YOU WILL sit further forwrads as the handlebars control where you sit and not you - even if the seat hump is at 45 degrees forcing you backwards (so you'd think) you still would manage to sit forwards. the handlebars are everything when it comes to the seating position.

most of all, if you fit power steering with damping and go to trailed steering you will "turn on a sixpence"
not only that but with the driving wheel not driving into the front tyre contact point with the ground, the hysterisis of the front tyre has time to recover grip. the trail you run will be a damper allowing the tyre to re-grip.

c'mon, you know it makes sense? now do it! :kick: :thumb: :thumb: :lol: :lol:

How to jack the rear and lower the front of your original chassis for testing
Image
until next time!

regards

Taffy
Last edited by Taffy on Thu Oct 26, 2017 9:34 pm, edited 2 times in total.
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Taffy
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Re: Rake angle and grip

Post by Taffy »

would anyone care to make some useful input? :phone: anyone want to say if it is a good idea or not and anyone want to mention any experiments that they did that make you think this is heading in the right (or wrong) direction?

I can't work out if people don't know, that they don't care anyway, that it is over their heads or WTF anyway!

I read only this week that 90% of grip is a result of downward pressure on the tyre.

I didn't know that? I also was told that someone used their 21" as it was more stable than a 20" on a rough track onew day. is the 20" used for better grip or better steering? stable steering or grip?

we have a Month after Canada heights before the weather wrecks things.

I hope the last photo (above) is of benefit to anyone wanting to test a steeper rake at 'no cost' (shall we say "LOW COST" :-D :-D ). if you can't do the adjustments on any eccentrics then it will have to be done on a stiffer spring or one with more preload on it. if you can take into account the harsher ride then it is still a good test. the front can be dropped by just drilling 2 x 3 new holes. the shock mounts aren't so easy but I know some of you have a set of long and short front shocks. going long to short (should this be your lucky situation) would be perfect.

so anyone?

Taffy
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shaun
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Re: Rake angle and grip

Post by shaun »

Taffy,
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Re: Rake angle and grip

Post by shaun »

Taffy, 99% of the people aint got a clue what you're going on about. We briefly spoke at Long Buckby and I can appreciate what you are trying to explain, but I think it's falling on deaf ears. I understand your theories, but I think if you want to progress, the way forward is hub centre steering!!!
Taffy
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Re: Rake angle and grip

Post by Taffy »

cheers Shaun, your point is well made! :-D probably a good point as far as the regular crews are concerned but maybe the ambitious teams need to soak this up.

as for the hub centre steering: now your talking! :beer:

Taffy
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Re: Rake angle and grip

Post by Taffy »

Image
above are the forces when cornering. clearly, it is the rider who is in danger of tipping the outfit over.

remember the trick of standing on the end of the see-saw while yer mate went up past the middle (the fulcrum/pivot) and the more YOU weighed the further he could go? well what is needed is to split the rider and passenger up MOMENTARILY. this is at the apex of any given bend where the maximum grip is needed. you are fighting the centrifugal force so it isn't just WEIGHT but how HIGH it is placed. so it needs placing low and at the VERY BACK.

after this they can both move nearer to each other. infact if the passenger stays by the back wheel he makes a swinging pendulem effect so it is best he comes forwards again. the rider also wants to come back and sit centrally. BUT HE NEEDS TO BE ON THE FRONT END TO GET THE GRIP.

below is a cropped photo of the split (you can do this wiv bruvvers! :thumb: )
there is the question of whether - given the passenger needs to move forwards again - whether he should rest his chest on the seat for some corners so he can slide forwards and then on others hop over the side. use the right leg behind the standing left and against the silncer exit to press against.
Image
I see this as an extra dimension and skill to passengering. :thumb: the skills needed just got greater!

below is the best known frame of all time! the featherbed! made in 1949 by Rex McCandless of Belfast it has a twin downtube which sidecars have forsaken. looking at the headstock area: a perimeter frame protects the lower headstock where the vast amount of forces are. I have added a simple pair of diagonal tubes for lateral support which a solo doesn't need. the downtubes should meet at the lower end though and the whole lot plated in. quite why bikes have a perimeter UPPER headstock support - I can't understand but a rider can't sit forwards while the frame is like this.
Image

with the above the rider can get forwards.

underseat fuel tank.
have a look at the video below.
12 seconds = good view of the tank
43 seconds = fuel cap in the seat
http://youtu.be/HNyiqwC--KI
7.5 litres
you can get yer tackle right up to the bars now! :kick:

1) get the petrol tank under the seat for mass centralisation.
2) have a seat that's flat and goes up to the headstock instead and that is LOW, LOW, LOW.
3) split the rider from the passenger on tight rights.

a major help would be a passenger wheel that helped steer and so could be moved forwards. this can be done.... :phone:

regards

Taffy
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Re: Rake angle and grip

Post by Taffy »

the subject for tonight:

a modified chassis on the cheap!
ways of getting the rider forwards
cheating to get the 'load' on the front


a modified chassis on the cheap!
firstly I don't think I explained clearly enough how you can try a steeper headstock with your existing chassis without it costing a fortune! you'll have about 3 weeks good weather left this year so why not spend a couple of weekends getting the outfit ready and then go try it. go with another team; one altered, one standard and swop and try them together?

what you want is a steeper headstock and its going to take some 3-4 hours work but best to record everything you do on a sheet. I designed these sheets for myself about 14 years ago but you're welcome to them for free of course - cos I love y'all!
I can't put a word doc up here so this is a .jpg, if you want a copy just email david@taffmeisters.co.uk it is an example of what I do to solos. changes since the last ride, then in 5 boxes at the bottom how each short ride wnet and changes made. all settings have a row of before boxes and then after. very handy for when going back to a track once per year?
Image
one thing I would do though for ScX is have a before and after for the balance of weight of the outfit with rider and passenger aboard - that is balance between the three wheels. you've also got to add the third wheels supension settings, then there is wheel sizes. there is probably no need for you to know the shim stacks inside the shocks but you do need to know which set of shocks are fitted. use a stick between your headstock and the riders navel and do it the same everytime. 1cm is one kilo...so is the stick funny now? yeh I think it is too but you know... do this in the privacy of your own shed OK....no one need see! :lough: :lough:

by the way, I used to use the scales at a waste paper merchants between fork lift drivers mowing me down (unsighted of course), brilliant set up: one wheel on, then the second, sit forward - sit back and watch the scales move. :thumb: :thumb:

Image

look at the above photo carefully and the yellow lines; they represent the bike as it stands in the photo. so the yellow line is the angle of the swingarm etc
the red line will be the new angle of the swingarm. to put the end line back on the wheel spindle means the SA pivot will be jacked up higher, you'll have to imagine that!
the engine needs to be at the same angle inrelation to the swingarm as it is with the yellow lines so that means that the front of the engine must be lifted on the front engine plates etc.
at the forks, because you have jacked the rear, the red line is now ahead of the yellow line - the new position.
By drilling the pivot holes higher at the base of the fork legs you can see the red of the legs now below the front SA pivot. but the swingarm is in EXACTLY the same position horizontally - this must not move!
if you look at the top of the front shock mounts, the old (yellow) holes are below the (later) red holes.
The front swingarm is in exactly the same place and level as before. so i've shown the red and yellow lines almost on each other.

firstly, to drop the front end making the steering steeper. measure from the workshop floor up to the front pivot bolt. the pivot and the front arm must be the same height off the ground after the forks have been dropped as before.

for every degree you change the headstock angle, the trail will change by about 2mm. so if you steepen the outfits headstock by 2.5 degrees, you must put the front wheel back 5mm to get the same TRAIL. the next year, you ask for this new headstock angle but with the headstock another 5mm further forwards and then you have the trail you wanted but also your original wheelbase and balance back etc. remember these are isolated tests to see if there is an advantage and not the end of the test.

have you got a digital spirit level? £24 from Hong Kong on ebay! - get one!
http://www.ebay.co.uk/itm/Digital-Angle ... 5d508ec4a6
you put one part vertically and the other against a forward facing panel but in line with the wheels - measure the angle, doesn't matter what it says coz you want a before and after figure! sure it is nice to know the headstock angle but it is a round tube with bumps....not so easy for consistant results. :oops: the downtube going uner the engine might be a good one?

Image
we don't want to disturb the angle of the bottom arm or the suspension, so you need to drill new holes. look at the photo below and note that the red holes are all above the originals and about 5mm backwards. this is correct for the same trail give or take a millimetre.
Image (photo courtesy Jones, A.'Bromhead' VC DFC GC)
drill the holes as much higher as you can or dare on the vertical forks or if you have shorter shocks by 30mm then do the holes 30mm higher if you can and go to the shorter shocks straight away. even if you don't play with the rear you have simply drilled a bunch of holes at the front and used your shorter shocks for a test!

if you don't have shorter shocks then re-bolt it together and you need to get the shock(s) top mounting higher up the legs if you can, if you have drilled the fork leg holes 15mm higher then ideally you'd have the top shock holes 15mm higher. ALL THAT HAS CHANGED IS THAT THE FORKS ARE NOW IN THE RED HOLES FROM THE DIAGRAM. the horizontal arm should be the same distance from the ground.

at the rear
there are two ways of jacking the rear:
1) any kind of jacking you can do without touching the suspension. get the arse end up. taller rear wheel and tyre? eccentric chain adjusters with the wheel spindle at 6 o clock? eccentric on the shock linkage system? some people have a linkage that jacks the rear? longer shock? just get it up!
2) put lots of preload on the spring and prepare for a bumpy test? (try to avoid this one unless you know how to separate suspension from handling when testing).

then jack the chair wheel as well as best you can. best is if you had a taller wheel/tyre, great! 16" to 17" for one test? the SA is so short it'll slightly change the way it works otherwise. I once saw someone had welded a whole new eye for holding the wheel underneath the sidecar platform! do it if you can as you don't want the outfit to lean left or right anymore than you had it before. you are trying to isolate the test to one area.

if the worst comes to the worst you can harden the rear suspension a little and soften the the front a little (say one turn of preload max). please take this into account later..... :whistle:

finally, if you have jacked the swingarm on the rear AT ALL, you must raise the front of the engine. this must be treated as if you had a siezed engine to swingarm so that as the arm points steeper down to the rear wheel, the more the engine pivots up. a simple system is to use an enormous ruler and mark two points on the SA and the third right at the front of the engine.
Image

so now you have jacked the outfit what does that mean?
you should weigh it again with the crew on board (using the belly stick!) and the weight will have gone to the front significantly.
more weight on the front is more grip.

what happens to the geometry?
if you jacked the rear without touching the shock then did the engine position and the passnegers wheel as well = you haven't done too much, you have raised the C of G about 10mm I suspect.
you will have less trail by about eeeewee? say 4-6mm. :?:
to get this back, which you should ideally do, you would make sure that the red holes are not just higher than the orignal holes below but back a little, by say 5-6mm. this gives the same trail as before.

if all you are doing is jacking the rear for this test to steepen the headstock, the trouble is, to get the trail back you need to go back a hole on the forks. sadly, a hole is about 15-20mm (centres) and NOT the 3mm you were looking for. by the way, if you do only one end it is 3mm lss trail, if you do both it is then 6mm.

if you'd had eccentrics like I keep telling you to, this could be just a 'turn and lock' and away you go.... :dontknow:

another way of getting the trail right is to take a measurement off the front engine bolt to the wheel spindle and work it out as this is a "constant".

this whole test is about weight on the front. if you like it and the digital spirit level says you jacked the outfit by about 2 degrees, and you're happy then keep it!

and don't complain about the suspension if you adjusted it: "oh it handles like a dream but its too hard now! - lets call the test a failure then shall we?" :burn: separate suspension from handling!!! if it handles better, change the suspension afterwards! :whistle:

if you really, really like it then re-weld the platform and rear subframe lower again. get the rear suframe down to the same distance over the rear spindle nut again that you measured from. it's not rocket science....and the platform as well for the passenger otherwise he'll need a ladder just to get on the back!
order next years chassis with the new superdupa headangle - and 5-6mm further forwards to get the same wheelbase back.

getting the weight further forwards (without rabbitting on about the rake this time... :blbl: )
I said that the rider needs to get further forwards all along and failed to point out that the outfit would tip over if the passenger came with him.
firstly, what can you do without separation of rider and passenger?

so how can you cheat the system? well, here are three easy enough reasons and a fourth at the end
well the handlebars are perhaps too high? if the hands are above the elbows there is no downward pressure.
just as an experiment on that weigh bridge I mentioned at the papermill: turn the bars upside down and ask the rider to lean into them - straight away a 3 -5 kilo transfer to the front! I know it, I've done it. all the rider will needs to do is stoop more on landing jumps - simple as - after throwing themselves into the radiator: this is no problem! :-D
Image(thanks to Chris Helm)
the handlebars would have to come down and back a little due to the 'whip' when landing a jump. look up the list of bars available from Renthall, they give you height, sweep, width etc.

secondly, move the fuel tank from its traditional place and then extend the seat forwards and down. the rider weighing 180LB makes the biggest difference and every CENTREMETRE is a kilo.

thirdly, sit lower still if you can and get the frame designed with this in mind. there is no need for these high frames when all you are doing is connecting the headstock to the SA pivot. that's all you are doing. the rest of the frame is "ancilliaries" after this.

these three above start to change things.

pendulem effect
this splitting of the rider and passenger creates a pendulem effect as said 2 weeks ago - not good after the apex. here below is why the rider loves to sit in the middle and be in control of all his senses, peripheral vision, awareness, horizons etc:
Image

interestingly just when you think about looking at racing cars etc, it is bikes that come closer to our sport! :thumb:
MX riders slide back and forwards
speedway riders slide back and forwards
roadracing sidecar passengers slide back and forwards
anyone not strapped in in a 4-wheeled sport MOVES AROUND.

so ScX rider's need to too! there's no rule against a 'driver' being forwards of centre. Alan Jones et al from the 80s in F1, Novalari in the pre-war Auto Union etc all were on the front axle.

the fourth thing you can do is 'MASS CENTRALISATION'
if the rider wants to sit further forwards we need 'MASS CENTRALISATION' between all 3 axles. with the radiators back we can send the rider forwards.
how do you get that?
really, really easy! - on paper! the theory is easy - doing it is another thing LOL!!!

as an experiment, some of you have a sidecarX outfit MODEL right? you know...6" long and 2" tall sits in the window cill at meetings. hang it up by a cotton thread at three points and draw the lines similar to the engine photo below. where these three lines cross is the C of G in plan (2D, not 3D OK?)

you all know a workshop with a hoist right?

you remove all fluids and then hang the outfit at three different points. let us say from:
the headstock,
the platform near the rear wheel spindle.
the sidecar SA pivot.

three static and solid points that aren't moving. if you could freeze in mid air all three pieces of string, they would all meet at one point!

I did it just a week ago for Dutchman who came and stayed to study all these things and we did it to my 570 engine. as you can see, we hung it from a doorway and felt-tipped the engine cover, look how accurately all three lines intersected! sorry about the quality...
Image
the lines all converge to one point. I can't give you the centre of gravity of that engine because it is inside the engine but we can find the C of G on a sidecar because it will be in mid-air. we could do it on an outfit so you get the true CoG in 3D.

if you doubt this, ask yourself where the centre of gravity is of a horseshoe or a dougnut! it's somewhere in the middle - in mid air!

you hang the sidecar and a plumbob from a hoist. make a note of how far above and over a wheelarch etc the plumb bob is and then do it the three times. afterwards you get three people to hold three pieces of string at the same angles and they will all meet at one point over the chassis somewhere! measure it, mark it, note it. :shock: :shock:

what you want is as much weight around this single point as possible - fuel especially so that the weight of the outfit, its balance is the same from the start of the race to the end so that the rider can always ride hard! below is a photo from last weekend (thanks to Chris Helm)
if you look, there is a dusty area that Scott, the passenger, hasn't walked on the platform.
Image

failing all the above you need to think about splitting the rider and passenger up. do it by the minimum but the diagram below shows that the passenger has greater effect the further back he goes.

think of this film...
the italian job
the final scene
the coach over the mountain's edge (Michael Caine: i've got a good plan lads...)
8 can't go after the gold but 1 can if the other 7 go and stand with the driver right?

back to ScX....
so the rider can move forwards and the passenger can adjust by coming towards the rider on some corners and away from him on others.

on a tight right hander where the outfit suffers from understeer, the rider moves forwards but the passenger must move or 'adjust' so the rider is safe. This is just like roadracing. with the rider trying to get as much grip forwards as possible, the passenger adjusting his position by 'feel'.
Image
as you can see from the diagram, for the passenger, the further back, to the right and down low, the safer the outfit. now don't get me wrong, the less the rider and passenger are apart the more centralised the 'mass' of the crew. so the diagram is an exageration so you understand the maths of it. if the other things I have recommended here worked first then it is all worth it, right? :sweat:

why do they have to be together, why not apart at the apex and then back together leaving the corner?

the rider's weight will always want to tip the outfit over BUT he is stuck steering the outfit so the passenger's weight DOES matter because he can move away. the bottom line is that only 'X' amount of weight can move forwards without it tipping the outfit over but you can move it forwards as long as it moves Forward and DOWN!

the only difference is that the passengers force outwards is protected by the passenger wheel. having lots of trail would also do this but that is another story...
(imagine you are sat on a supermarket trolley and you are right at the front turning right, as you turn right your left front wheel has moved outside the trolley and now you are less likely to fall over! whereas if the left wheel just pivoted under its axis, the wheel is still under the trolley).

back to the mass centralisation idea....
below is an airbox idea with the radiator in the middle of the bike. under the rider's thigh is the fuel INBOARD of the bike. the exhaust can has been put by the rear wheel to help - well you guessed it - right handers!
Image

add these ideas together with this design:
Image
the fuel tank is gone, the steering more upright, the rider is lower and can move backwards and forwards. the passengers tail piece is super-extended for those hairpins to the right so he can sit back further all on his lonesome. polish it up and he could slide forwards after the apex and join the rider. the radiator, nearly under the mudguard is there just as another option - just for kicks! by the way, if you take passengers and low CoG seriously you would have a mudguard with the high point in the middle and not a duck tail with high edges as at present ...... that way the rear tyre would come up and INTO the rear subframe tubes..... seriously, what a cock-up! :hit:

below is a greeves, the rear subframe could be lowered so that the rear wheel pounded up INSIDE the rear subframe. make that mudguard out of plastic - passenger slides too-and-fro what? 3" lower than before?
Image
no jokes about asking you all to win on a Greeves PLEASE! :-D :-D

I took this photo in 2009 while helping Mark Kinge. I couldn't understand it then and 5 years later I still don't understand it.
Image
what is the radiator doing here! outside the wheelbase? and riders say that they can't move forwards! :dontknow:

so what goes wrong when outfits try to to tip over going around a right hander?
if you have a big heavy rider, the passenger must be big and heavy as well to counter balance him.
if the rider is light (and young like 3 of the young GP brigade are) then he'll probably suffer from a lack of front end grip because he just can't get enough weight ON THE FRONT WHEEL to weigh it down.

if he's tall, and built like a welsh pit prop (Aled!) and his passenger is also big then the trouble may not be front grip but the TIPPING ACTION because having got the grip with the weight, the outfit then wants to tip because riders sit high up! the difference is weight and where it is: the crew weight is always high up. it's because the rider is heavy that he's getting grip. its because it is high up that it is tipping over!

in the future: frames that therefore link the headstock with the swingarm pivot allowing the rider forwards while staying low are therefore vital. the rider must be able to move. the fuel tank must LEAVE the headstock area. if you have a 4T Fi then it doesn't matter two figs where the tank is because you have a fuel pump anyway!! do they have the internet in Frome? :-D :-D

none of the above is about running lots of trail this time, its about simple stuff that you should be looking to do anyway. it has nothing to do with the chair wheel and the compromises that you have to make there.

regards

Taffy
Last edited by Taffy on Mon May 04, 2015 4:41 pm, edited 1 time in total.
I don't want a works bike I just want their address book! :?: :?:
here is a link to the SMCA web site for ya! http://smcagb.moonfruit.com/ :-D
Taffy
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Re: Rake angle and grip

Post by Taffy »

over 3,050 visits which is 50 a week since the thread started. :blbl:
sorry 3,150 since
sorry, 3......................... :lol:

having not read it for months, I've just edited the above post considerably to make it easier, I hope, to read!

hve a look at these bar risers headstock change and bars multi adjustable. sorry about the whinging dingo lover...
https://www.youtube.com/watch?v=KvYdZ_z9-HM

regards

Taffy
I don't want a works bike I just want their address book! :?: :?:
here is a link to the SMCA web site for ya! http://smcagb.moonfruit.com/ :-D
Taffy
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Posts: 326
Joined: Sat Aug 09, 2008 12:02 pm
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Re: Rake angle and grip

Post by Taffy »

http://www.steves-workshop.co.uk/vehicl ... kindex.htm

this has got to be the way to go surely?

Taffy
I don't want a works bike I just want their address book! :?: :?:
here is a link to the SMCA web site for ya! http://smcagb.moonfruit.com/ :-D
Taffy
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Posts: 326
Joined: Sat Aug 09, 2008 12:02 pm
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Re: Rake angle and grip

Post by Taffy »

well who'd have believed it: 5,710 views as we speak!
5,610 by Dutchmen who can weld: you know who you are!
99 views by Englishmen who were looking for the recipe for a cocktail drink
one well educated Welshman!

so what has happened in two years?

well nothing really! bikes have got faster, Browny and Willemsen are older and still at the front proving that guile and wisdom account for a lot in racing.

I've been involved with suspension mainly as I'm not the rider and it's not my machine. Sadly, most suspension is set up by the leading company, their figures are often wrong and the rider's believe every word they're told. their figures for sags are wrong, the springs they recommend are wrong and well, let's just leave it at that.

a damper wants to lose around 20% of its travel at rest on the wheels with the crew on board, this transpires to around 65mm race sag but somehow, nearly 100mm is still OK? last week a rider with 18mm of preload was told it was fine and last season a 30 stone rider was told to use the same spring as everyone else :dontknow: :dontknow: :dontknow: Progress in chassis design is nigh on static. To make something lighter is always a welcome improvement though and with the outfits getting ever so slightly better then obsolescence is guaranteed and just what the designers want. next year's product again everyone? more of the same? good!

with the end of the 20" tyre nigh, someone (ahem, a-he-mmmmm -thank you!) introduced the 2.50 x 21" rim to the paddock with a choice of nearly 70 tyres instead of.....2!!!!

for those interested, the loop must go forwards one hole and one size stronger spring fitted. surely you've all been running "mix"? no....OK, well one spring stronger anyway. the tyre is superb over really rough ground and braking is an improvement over the 2.15 x 21" and equal to the 20". fact is though, Michelin re-enter the equation and now you're talking of the best....

this would normally be the end of it: a tyre with more grip....but this gives riders a chance to load the front (loam soil) which can only really be done by jacking the rear and 75% of that figure to the sidecar so the wider rim and tyre are only the half of it.

I have designed a front swingarm & fork instead of a loop & fork. so what is it? well what it is, is in the name! from this you'll know what I've done and then how i did it. this gives 5" of quality travel instead of 2" (trying to fox the Dutch here but they'll only Google it-damn them!). the weight and strength are the same. Production of hundreds and thousands of these items starts next week and we intend swamping the market just before leaving the EU. that's our Brexit deal!

if you're Dutch you will think long and hard.......... the English though, are making cocktails! :blbl: we know how to come second! :thumb:

will the situation be the same in another 2-3 years? yep

one last thing, Kevin Hollister made brilliant chassis and they are only now matching what he made 5 years ago in handling. He knew what he wanted by making 2 chassis per year not 20, he didn't even visit the races or sponsor a rider yet was 5 years ahead of the game. Kevin filed for bankruptcy last year and now works weekends paying off his debts. quality guy. more than you can say for the three wheeler who broke him and put him out of business.... His most recent rider was telling me that his VMC is 15 kilos heavier and doesn't handle as well.

Achtung Tommy's: buy the best next time, it was under your nose!

Taffy
I don't want a works bike I just want their address book! :?: :?:
here is a link to the SMCA web site for ya! http://smcagb.moonfruit.com/ :-D
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