what teams custom make steering racks?

[Fyhr]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Fyhr:
[QUOTE]Originally posted by Kyle "steering and suspension":
i have seen other teams use a similar system, do you find this gives you less play than a simple intermediate shaft with universal joints of some kind? how do you adjust your clearance between rack and pinion? </div></BLOCKQUOTE>

The first revision used flat solid shims between the pinion bearing lids, the second revision used hard rubber shims to allow higher tightening running with higher interference while retaining some elasticity to avoid lockup (if i recall correctly).

The bevel gear does not give less play than any other solution, in our case it was a large source of play, especially after running for a few competitions. I believe the reason it performs poorly is the bevel gears only being held by a keyed joint, with no possibility to shim the gears together. In a recent discussion with a transmissions professor he suggested using belville washers for shimming the gears together, yet again allowing high interference without lockup, this would however increase friction in a steering system that is already fairly grave.

The reason we used this solution is packaging, on these cars we've run 10" wheels with 7 deg caster, there was simply no room for the steering arm low-front on the upright.

On the most recent car, the team have moved away from the 90deg gear and run low-front
steering in 13" wheels, here is the rack.



We also purchase our gear components, again if i recall correctly, we've used modulus 1.5.

[Dr Tron]

looks great, any issues with those gears being exposed?

[Fyhr]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kyle "steering and suspension":
looks great, any issues with those gears being exposed? </div></BLOCKQUOTE>

Lack of lubrication, this car isn't finished. I think there's supposed to be a cover plate over the gear.

We've never covered outer gears on the rack though, i guess we couldn't find a small enough rubber cover, so we just run a thick moly-grease.

[buggaero]

We'd installed a custom rack and steering , in 1.5 module and it saved us around 4-5 pounds than our previous car.
The only problem in the design was , it being not easily disengage-able. It wasn't CNC'd but the lathe guy just buffed it to mirror finish. So can't say it wasn't neat.There surely some play, although minimal, in the end bushes of the rack after the event.


Mechsonic Racing.
New Delhi.

[Dr Tron]

yes this one saved us a significant amount of weight as well and the amount of play is not significantly worse then previous bought racks however I would like it to be better and just recently locked down a design for adjustable lashing on the next rack.

I machined every part of this rack aside from the carbon fiber housing (bought and then machined to fit) and it was a real learning experience as it was my first time getting some experience in the machine shop. I learned alot obout being paicent and doing things right the first time as well as having a plan before entering the shop. as you can see it is a pretty sturdy unit right now and with some careful planing and intelligent design alot of weight can be saved, right now im excited to get into the shop and put my plans into action... sadly i need to make revisions to the cad model first

[Dr Tron]

note those clevisis were not used, just a rough draft so to speak

[Fyhr]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kyle "steering and suspension":
note those clevisis were not used, just a rough draft so to speak </div></BLOCKQUOTE>

Do you use the cogged rack all the way or is it attached to some hollow profiles for the bit out to the clevises?

One quick (but minor) weight reduction you could perform is to get a 45 deg end mill and just add a chamfer to the pinion housing.

All in all it looks really neat, the clevises are very similar to the ones we've used, the only difference being the slots for the rod-end mount were milled with a round end mill.

[Dr Tron]

it is not cogged all the way however the rack set is attached to one solid piece of aluminum whos diameter steps down beyond the section the rack is attached to. next-gen will have hollow attached sections which you might thing would be difficult based on the pinion providing a force on the center and it being supported only on the outside however if you look at on of the installed in-car pics (i will repost as they are not able to be viewed because i moved some things around) you can see a bolt going through the bottom of the pinion housing; this holds in place a section of bearing grade bronze (same material used on both the endcaps as well as the pinion gear plates) machined and polished with a chamfered flat spot the rests against a flat spot machined into the "rack" both helping prevent a large bending momment as well as help in preventing rotation of the reck in relation to the pinion gear.



here (below) you can see the bottom bolt



exploded view (giving away my secrets) but pretty early in production (aka still plenty of secrets) also the tape was on for cutting and fitting simulation of epoxy

[BMH]

^^ Very Nice! Do you have any numbers in terms of weight and steering ratio?

[Dr Tron]

3.4 lbs vs 7 and 9 respectivly for our previous bought racks, Rack ratio is about 3.14:1 depending on lashing and i would have to double check some math on suspension geometry to get an overall SR