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Author Topic: Rack and Pinion steering  (Read 112 times)

StefanN

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Rack and Pinion steering
« on: 20 May 2019, 12:11:04 pm »
I bought a relatively cheap rack and pinion set from eBay that's advertised as for dune buggy or golf cart, to find out if they're any good.

The photos below give you a good sense of the size of the unit and what's inside.   Travel is 10cm lock to lock and that is 1 revolution of the pinion.

The main issue I can see is that the pinion is only loosely located by the central casing which is some sort of plastic and so mainly to keep the dust out and grease in.  It's possible to do this but would need something that is low effort/achievable without specialist machine tools to be worth while buying the unit in the first place.

Anyway, thought I'd share this in case others have been wondering what the units are like.

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StefanN

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Re: Rack and Pinion steering
« Reply #1 on: 20 May 2019, 01:37:03 pm »

Steve Cole

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Re: Rack and Pinion steering
« Reply #2 on: 20 May 2019, 11:11:58 pm »
Iíll look forward to having a look at this at Stretton, maybe we can use these with a couple of improvements

RhysN

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Re: Rack and Pinion steering
« Reply #3 on: 21 May 2019, 07:45:17 am »
I continually ask "Why?"
KISS
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Little French

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Re: Rack and Pinion steering
« Reply #4 on: 21 May 2019, 07:49:07 am »
Hello,

I bought the same but not used yet, I also think that it is necessary to strengthen the plastic part of the center ! ;)
Aging is mandatory, growing up is optional .....

Graham Hill

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Re: Rack and Pinion steering
« Reply #5 on: 21 May 2019, 12:21:10 pm »
I know Rhys' feelings on rack and pinion steering from previous and although I am new to karting technology I can see where he is coming from.
The karting 'Pitman arm' is light and simple and although initially disappointed, I have now managed to get mine adjusted better. It still feels over-sensitive at slow speed (compared to a saloon car) but it is fine when driven faster and is great for quick opposite-lock when pushing hard.
The adjustments that helped me were a combination of shortening the Pitman arm action, together with stacking the steering rod ends (in lieu of side/side).

For those keen on pursuing rack and pinion, Gemini Karts do have a robust alternative on their website, under 'compact steering rack'.

Also on their website can now be seen Geoff May !!


Slack Alice

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Re: Rack and Pinion steering
« Reply #6 on: 22 May 2019, 01:53:07 pm »
Hi guys.   Iíve officially got the go ahead to build!  More details to follow, but Iím going to use one of those racks! I think the KISS principle works here. Iíve  only driven a kart a few times but the steering is heavy. I reckon the build will be simple with a rack system. Iím going to mount mine on the axle!

Graham Hill

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Re: Rack and Pinion steering
« Reply #7 on: 22 May 2019, 02:49:44 pm »
Congratulations on securing approval Dave (David/Dave?).
Please keep us updated with your progress on the build forum as it develops.
Ooh, shut that door!

RhysN

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Re: Rack and Pinion steering
« Reply #8 on: 22 May 2019, 10:15:32 pm »
I would much rather you didn't mount the rack on the axle, as per my emails. Steering on a cK does not need to be heavy, two finger on mine have been the norm. we don't have wide sticky tyres to deal with, and sensible geometry will have nice, sensitive steering.

Slack Alice

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Re: Rack and Pinion steering
« Reply #9 on: 23 May 2019, 08:27:18 pm »
Iíve been thinking about this rack and pinion lark all day!  With a beam axle, the only way to get true steering is to use a steering box, steering arm and drag link.
Bump steer is eliminated.
Even pitman arm steering is wrong because it introduces a different pivot point when the wheel bounces. Bump steer is inevitable.
Rack and pinion is the same. Different lengths ie a beam axle of 1 metre and a steering arm of perhaps 300mm...bound to cause bump steer.
The only way to eliminate bump steer is to mount the rack on the axle.
I really canít see why this is an issue?
Several Americans have used a rack, mounted to the front chassis member, and the comments was ďalmost almost eliminated bump steerĒ. Say no more.

RhysN

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Re: Rack and Pinion steering
« Reply #10 on: 24 May 2019, 09:05:45 pm »
Bumpsteer can be eliminated in numerous ways, that's not the only way. Consider that the phasing of universal joints in the steering column is vitally important and the free movement of the change of length  of the column as the axle moves through it's travel is equally vital. If it was the "only solution" don't you think the method would appear in a huge number of full size car systems. A friend of mine was killed in an accident solely caused by someone else using an axle mounted rack. Need I say more?
« Last Edit: 25 May 2019, 09:15:44 am by RhysN »

Slack Alice

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Re: Rack and Pinion steering
« Reply #11 on: 25 May 2019, 09:12:12 am »
OK. I think to minimise the effect due to unequal lengths, the suspension could be made stiffer?
I did some sums yesterday and came up with about 150lbs  acting on the front crossmember. Is this about right for spring manufacture? Say about 50mm camber in the 1/4 elliptic springs over about 400mm?

RhysN

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Re: Rack and Pinion steering
« Reply #12 on: 25 May 2019, 09:16:56 am »
Maybe a little high on the load. Those leafs are still sitting here when you want them. £10 plus post.

Slack Alice

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Re: Rack and Pinion steering
« Reply #13 on: 26 May 2019, 04:30:31 pm »
Iíve thought of an unusual way to decrease the difference in length between the beam axle and the relatively short steering arm ( about 250mm if using a rack).
Mount the rack at a slight angle ( to the chassis!) and attach the left hand side rack end to the right hand steering arm. The right hand rack end goes to the left hand steering arm. This would increase the length of each steering arm by the length of the rack!
What do you think!
I will have those springs that you are offering please Rhys. Iíll email address details and you can bill me somehow!

RhysN

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Re: Rack and Pinion steering
« Reply #14 on: 26 May 2019, 06:06:21 pm »
As we are talking R&P, I have been emailing with my best CK buddy in NZ, people who were at the builders meet will understand why we have been talking together about yet another crash in the US. In this case we have seen the video, and both come to some conclusions, copied below are Mike's thoughts for you all to consider. I am changing what I was going to do on the Napier as a result.
 "I am starting to think light cars and drivers may not be such an advantage. As I replay the Vauxhall roll in my head I am convinced it wouldn't have rolled with me sitting in it. Not because of ability just the way it flicked. once Justins weight was jerked into a different trajectory the car tipped too easily. Would a heavier one have just spun? Small tires didn't appear to help matters.
The yellow car and even Als T push a lot then go quickly to oversteer. see how the yellow guy is so wide by the wall and in limited control.
Brians de dion has one of those little racks in it. its 1.5 turns lock to lock and on windy gravel roads isn't really fast enough. The Renault is 360 degrees lock to lock and is even a little slow when playing around trying to hang the back out. I think al has put his in the wall at slime dog,"

I have driven the car "Als T", at a Gittreville event last November. It has a steering box, and the first corner scared me witless as it felt totally disconnected, a few laps and felt more in control, but with the geared down steering I could not catch up with the need for opposite lock, only option to stay out of the hedge was go slower.
I have probably driven close to 50 cyclekarts, and I still can't see the need for anything other than the "go kart style", unless you can't move from the feel of a power steering Cadillac