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Cutting down an escort steering rack to reduce bump steer?
alister667 - 12/1/05 at 11:20 AM

I was just wondering has anyone tried cutting an escort steering rack down in size (similar to what MK do with the Sierra rack) to get the ball joints at the end of the rack to line up better with the suspension pivot points and reduce bump steer?
I've never seen this done on a escort track width locost, I have a mate planning on doing this and I was wondering why isn't this more common?
Is there a good reason it isn't done?

Thanks

Ali

David Jenkins - 12/1/05 at 11:42 AM

It certainly does get done - but maybe it's the justifiable mistrust of DIY welding that puts people off!
I know that i would want to know that the work had been done by a first-class welder before I took it on the road...
David

Bob C - 12/1/05 at 11:43 AM

I did this (took 3.5" off the rack & 3" off the housing), there should be a picture in my photo archive, there's definately one on my website. Note I use butchered MX5 uprights so my requirements might be different to yours!
cheers
Bob

Bob C - 12/1/05 at 11:46 AM

I was not too concerned about the welding; only the housing is welded & even if this completely breaks, the wheels are still pretty well located.
Bob

Cita - 12/1/05 at 05:04 PM

I chopped an Escort rack for use in my single seater and by chopped i mean that the UJ's of the rods are 20 cm apart now!
I was surprised that the rack bar wasn't hardened.I just cut through it with a hacksaw.
Took me about 1 1/2 hours to do the job.

Rob Lane - 12/1/05 at 05:42 PM

It's not difficult to cut and rethread the rack or to cut and weld outer tube.

One of the reasons it's not done is that the pinion end has to be moved inwards to get the correct pivot point. This then tends to put the downlink through engine or at least a component of engine.
It's not always easy to accomodate even with a double joint.

Cita - 12/1/05 at 05:54 PM

quote:
Originally posted by Rob Lane
It's not difficult to cut and rethread the rack or to cut and weld outer tube........


Nobody said that it was a difficult job

alister667 - 12/1/05 at 05:57 PM

Thanks for that lads.
I didn't think there was any good reason, it's just that I hadn't seen a book locost over here that had that done to it.
Cheers
Ali

Rorty - 13/1/05 at 03:32 AM

quote:
Originally posted by Cita
I chopped an Escort rack ...
I was surprised that the rack bar wasn't hardened.I just cut through it with a hacksaw.

AFAIK, a lot of racks are not through hardened. On some racks just the teeth are induction hardened.

Rorty - 13/1/05 at 03:42 AM

quote:
Originally posted by Rob Lane
...the pinion end has to be moved inwards to get the correct pivot point.

I haven't modified an Escort rack, but I've shortened plenty of other makes and what I did, was I shortened both ends.
The pinion ends get shortened first, and I usually allow a little leeway so I can put a PU washer on the end for a bump stop.
When the pinion end is done, I then measure the new rack length and chop the other end off to the required length.
Shortening the pinion end means you can keep it and the steering shaft over to the outside of the engine bay.
As Bob C says, there's no welding in any critical components, so there shouldn't be any concerns.
Steel rack housings can be welded back together with a MIG using a length of angle iron and a couple of clamps to align the two halves.
If you've got a TIG (or a friendly TIG owner), then you could obviously weld an alloy housing back together too. Most of the alloy ones I've done, I've simply slipped a tight fitting piece of tube over the join and left it as is. There's no real load on it.

erwe - 13/1/05 at 05:39 AM

Very easy, did it twice ona sierra rack.
Nothing is hardened, only the teeth.
Make sure that the hole for the thread is done on a lathe so it is in the middle (seems logic).

Rob Lane - 13/1/05 at 08:54 AM

Rorty,

On an Escort rack the pinion housing is cast and is also the end point of the rack, so it's not possible to shorten that end.

The opposite end of steel tube is shortened and the rack moved more central, this does usually cause major probs with fouling. The pinion comes out at around 80 degrees and doesn't lend itself easily to a double joint offset because of rack to engine distance.
I've seen a nice short, very angular, double joint, it comes from a Transit van and it's the steep 'downlink' through bulkhead.

'Easily' is the keyword in the above.

The rack is hardened on teeth only, hence cutting in the valley between teeth makes it an easy job. Getting a 'die' to rethread is the hardest part nowadays, so few 'real' tool shops left.

(I'm not a lathe man, hence the 'die' )



[Edited on 13/1/05 by Rob Lane]

NS Dev - 13/1/05 at 09:45 AM

Tell you what Rob, you're dead right on the tool shop front, but I have posted a very useful link on the Tools and techniques section which may help on this subject.

Bob C - 13/1/05 at 11:09 AM

here's a picture of my shortened rack on the car
http://www.locostbuilders.co.uk/photos.php?action=showphoto&photo=frsusp.jpg
You can see the sleeve where I welded the housing. You can also see where the pinion emerges - I would have thought it should be possible to miss most engines in this position??
cheers
Bob

Rorty - 13/1/05 at 12:11 PM

quote:
Originally posted by Rob Lane
Rorty,

On an Escort rack the pinion housing is cast and is also the end point of the rack, so it's not possible to shorten that end.

I hear what you're saying. When I mentioned shortening the pinion end, I was refering to the pinion end of the rack, not the rack housing. The idea (in my scenario at least) was to imagine the balljoint (on the pinion end) where it needed to be for the correct geometry, and then chop the rack to get the balljoint as close to the housing as possible, though allowing the pinion to remain within the chassis.
Though as I say, I haven't chopped an Escort rack and don't even know if it's desirable to move the pinion that far over for a Locost.
I bow to your intimate knowledge of the Escort rack.

Ian Pearson - 13/1/05 at 02:19 PM

The Yahoo list has loads of info on this as the Aussie Design Rules are very strict on bump steer. I can't remember exactly how much mine was shortened by, but I think it was about 110 mm. Had a local machine shop do it for me, and now have no visible bump steer.