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What's the thinking behind going for Zero Ackermann? It’s been around for a long time but seems most competition cars have gone this way Ackerman was developed back in early days for slow speed maneuverability, need to run 1 -2 mm toe out The concept is generating small amount of tyre slip for the inside wheel in a turn that’s necessary to obtain so called optimal tyre performance Apparently F1 has gone even more extreme a while ago with Anti Ackerman wheels look like something is broken when wheels are turning The WRC Cosworth Escort had multiple steering arms to choose from mostly it forged steel, sets for different ride heights, but the only Aluminum arms I could get where these I used as templates to make my own suspensionsecrets.co.uk/ackermann/ |
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Darkspeed
Club Retro Rides Member
Posts: 4,878
Club RR Member Number: 39
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Was more wondering why you had specifically chosen it for your application?
I ignore anything modern F1 - may as well choose geometry from an Artic' or a 747 for all the relevance they have with a roadgoing comp car.
My G27 has/had almost Zero Ackermann and it was impossible to push it with the steering turned more than a few degrees. It just scrubs out the tyres in low speed manoeuvring and in those polished type car park surfaces it just screamed its nuts off.
Anti Ackermann has also been about since Adam was a lad - IIRC Chapman was an advocate for a while - reduced drag on that unladen inner wheel which was mostly in the air anyway ! When he flipped the rack to ahead of the wheels he just swapped the uprights side to side and left the steering arms the same - full divergent.
Carol Smith was a less Ackermann advocate in his Tune to win book - citing similar that the loaded outer wheel tyre slip angle provides a form of Ackermann - However he decided that zero or anti Ackerman has to be wrong if the mechanics cannot push the car around the paddock. May explain current F1 cars needing a dolly or that they plough straight on into pit walls. But that full Ackermann was only goof for Hyde Park carriages
What he did do was complete u-turn his thinking around in his next book Engineer to win, and take twice as many words to explain why even more Ackermann works even better. However, his final note is that its very car and application specific - and reading between the lines - that whilst he may have thought it only good for horse draw carriages it actually works pretty well for racing cars with little in the way of drawbacks.
I thought maybe it was due to the 037 employing it.
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Try and push a Lola T70, 917 etc tons of front tyre scrub, but that does tell you how they perform on track, of course it’s all about how much toe out is used, I’ll have zero Ack’ as starting point if it proves not workable I can switch arms, when !!! I get to that stage it will all be decided & adjusted to optimize tyre temps
I have all those Smith and Staniforth books too 😄
Re 037 does have straight/ zero Ackerman and I will be using the tarmac geometry with additional ride height & gravel geometry locations
Though do not have any interest in running off-road
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Finally I have the Uprights!!! though the CV stubs are 4 weeks away from completion 2 Uprights I can use as they are for double A arm rear application, I went ahead with heating uprights on a 1 ring hot plate to about 220 F the bearings just slid in with slight drag, block of wood large ally punch and a lump hammer to make sure they were set fully home, I polished the black coating off the hubs bit anti seize they went in 3/4 way by hand tight sliding fit , needed a similar arrangement of backing Ally bar against inner race and hydraulic press to make sure fully set. Just to see how the steering arms and lower A arm fit, I mocked 1 rear up to take measurements on lower ball joint pivot dimension to, hub flange and where the top cut line is going to be to machine the Top Ball Joint location, I hope to achieve a low KPI (upright steering angle) 4* ? I will draw it out full size to see if I can achieve steering axis close to the center of the tyre contact patch    |
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May 14, 2024 16:31:04 GMT
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Skimmed tops of the 2 Uprights for the front ready for top Ball-joint location machining  Having drawn full scale 1 front suspension corner using 037 KPI of 4*30” I settled on 5* I will need to remake the steering arms as they have the lower Ball-joint in them and I need its location moved outward as far as possible to achieve smallest offset as possible “steering axis point to center of tyre” this is means replacing the 15x8 Minilites with 16x8 3 piece (like the rears) but with about ET30 v the current ET12  Set up Caliper with shimmed disc to check Brake Bell offset, it’s a nominal 20mm Caliper is forged Wilwood Superlite 2 4x 44.5mm with 296mm x 20.5mm UL disc |
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May 17, 2024 14:20:31 GMT
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Converting 2 front Macpherson type Uprights to double A arm spherical rodend type top ball joint  No going back, good old hacksaw  28* angle face squared made both Uprights same height  Drill taping drill size for M22x2.0 screw in insert that will have a M16x1.5 thread for the top ball joint bolt |
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