Rack and Pinion Steering

[StefansBus]

Hi all,

A friend and I have just installed a rack and pinion steering in my early bay. Some pics of the prototype "kit" and installation here: https://forum.bulli.org/forum/viewtopic.php?f=7&t=25532

It's a Opel/Vauxhaul early Astra/Cavalier rack and a T25 relay box plus a bunch of stuff designed by my friend. You'll see all the parts in my link.

Some metal work in the master cylinder mounting area was required as well as slight clearancing at the front beam between the tubes on the left side.

The steering is now very light due to changed gearing ratio (so it takes more turns form stop to stop) and is virtually without any free play.

I have noticed a decreased tendency to return the wheel to neutral out of a corner. I strongly suspect this is due to the motion of the tie rods which is now completely linear and was previously slightly "circular" due to the steering arm (idler arm?) at the centre steering bolt in the axle. This arm is now no longer needed so the inner and outer wheels turn at exactly the same rate, which is not quite the case with the original steering geometry.

I would welcome some feedback from others who have converted to rack and pinion as to whether or not the same has been observed.

Cheers

Stefan

 

[StefansBus]

Have had some good feedback on thesamba already. https://www.thesamba.com/vw/forum/viewtopic.php?p=8958514#8958514

Would appreciate any additional qualified comments, though.

Cheers

Stefan

 

[cunning plan]

Wow :shock:

Excellent engineering / fabrication work there! arty0021:

Thanks for sharing.

 

[gninnam]

Wow :shock:

Excellent engineering / fabrication work there! arty0021:

Thanks for sharing.

+1

 

[67panel]

You will have lost Ackerman angle as some is built into idler arm as you say, check castor angle as well and maybe add some more as that will make the steering self centre. Fitted polo rack to mine but it works relay lever so geometry is kept stock .

 

[StefansBus]

Thanks. Yeah, will check/add caster. Will also add fresh grease to NOS rack. It's pretty dried up in there which won't help. Might also have to loosen the rack and pinion a bit. It does have an adjustment screw. It is a little bit tight at the moment. Will see. Also the new tie rods are a bit stiff as are the not quite so new anymore ball joints. None of this helps with self centering of course. Not much I can do about the Ackerman angle, I guess.

We discussed keeping the relay lever but decided against it because its bushing is always a source of some play. I don't think the relay lever results in great Ackerman angles as the tie rods are so long that any change in angle only results in a small change in distance. But I'm sure you are right in that it does have an effect. I just don't think it's my only issue.

 

[cunning plan]

Fitted polo rack to mine but it works relay lever so geometry is kept stock .

:shock: Build thread?
oke:

 

[67panel]

pics on gallery spliffy build thread.

 

[cunning plan]

pics on gallery spliffy build thread.

Thanks, I'll take a look arty0021:

 

[StefansBus]

Thanks. Yeah, will check/add caster. Will also add fresh grease to NOS rack. It's pretty dried up in there which won't help. Might also have to loosen the rack and pinion a bit. It does have an adjustment screw. It is a little bit tight at the moment. Will see. Also the new tie rods are a bit stiff as are the not quite so new anymore ball joints. None of this helps with self centering of course. Not much I can do about the Ackerman angle, I guess.

We discussed keeping the relay lever but decided against it because its bushing is always a source of some play. I don't think the relay lever results in great Ackerman angles as the tie rods are so long that any change in angle only results in a small change in distance. But I'm sure you are right in that it does have an effect. I just don't think it's my only issue.

Quick update: Put some fresh grease in the rack and pinion. Also did another front end alignment. Camber was off on one side. Now in spec. Toe in in spec, Caster in spec (cannot add more). The self-centering out of a turn is already much better. I'd say 80% of what it should be. Driving the bus is if it had power steering. Steering response is also immediate. There is virtually zero play. It's like a different vehicle. Steering is noticeably less direct than stock but so much more precise.

Stefan

 

[StefansBus]

Further update. The front end has continued to break in and the slightly less pronounced self-return to center is now almost a non-issue.

A few people who know a thing or two about cars including, old busses, have now driven my bus with the rack and pinion conversion.

1. The guy who designed the kit. He couldn't believe how night and day the driving experience is. He is now working on a version for his late bay.

2. The master mechanic who owns a classic car garage/shop and helped us with the installation, alignment etc. Before he drove the new steering he probably thought the project was a bit unnecessary. After the test drive he said it was worth every hour and every Euro spent on it. He is not a man who gives much praise usually but he was full of praise for this conversion.

3. The local TÜV inspector (a government accredited automotive engineer) who inspected the conversion and amended the vehicles technical documentation to ensure the bus is still street legal, and thus insured, in Germany even after the conversion. Yes, we love our rules here :roll:

I myself wouldn't want to drive it any other way now.

Stefan

 

[ozziedog]

That sounds great Stefan. I’m guessing that even before the calculations of leverage here and there, you still have the fact that a peg and worm drive requires a lot of elbow grease (effort) to turn even before the rest of the steering starts to work.

Ozziedog,,,,,,,,,Thank you for the wonderful updates too :mrgreen:

 

[StefansBus]

Hi Ozziedog. You are most welcome. And I think you are absolutely right about the much reduced friction in this steering set up.

Stefan

 

[megabus]

Hi Stefan is a kit available for this steering conversion I have a 71' bay window.It looks fantastic many thanks Ian.

 

[Coda]

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