mistergrumpy
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| posted on 1/9/06 at 10:35 AM |
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Wishbone Sizes?
Was wondering just what it is that determines the required length of front wishbones? Chassis, steering rack? I'm going for the standard chassis
front from the McSorley plans so I gather my wishbones will just be as is in the 'book', but just got me wondering as I feel I'm
overlooking summat.
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phelpsa
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| posted on 1/9/06 at 10:41 AM |
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The steering rack, but you can make extensions 
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StevieB
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| posted on 1/9/06 at 10:45 AM |
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As far as I can gather, the wider the better (working on motorcycle principles, the longer the swing arm, the better the handling/smoother ride). And
obviously a wide car handles better through the corners.
Other than that though, I can only assume the steering rack is a general basis for the from track.
MK shorten the sierra rack and use extentions to the track rods, so I guess you can have whatever dimensions you want at the end of the day.
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mistergrumpy
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| posted on 1/9/06 at 10:48 AM |
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Hmm, so if I used book bones on a book chassis with a Sierra rack, would the rack have to be cut? Wonder if I can get around rack mods. Don't
mind the extensions to the track rod ends but rack mods seem a bit too much.
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StevieB
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| posted on 1/9/06 at 10:59 AM |
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The actual rack stays the same, it's just the casing that gets cut down and welded in the middle.
Having said that, I'd avoid using a sierra rack and go for the escort version, as the sierra item is a hideous and heavy unit.
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ecosse
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| posted on 1/9/06 at 11:03 AM |
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The width of the front bones will likely depend on the back axle width i.e. if using sierra/capri/cortina axles on a book chassis the front bones
would be best to be wider than book or it may look odd (not sure what it would do to the handling)
The consensus seems to be that all racks will be best shortened on a standard width chassis (to avoid bump steer), although the escort rack should be
a straight fit on a +4 chassis
Cheers
Alex
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nick205
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| posted on 1/9/06 at 11:09 AM |
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MK narrow the whole steering rack (casing and actual rack). the reason being to bring the inner pivot points of the track rods vertically in-line
with the inner pivot points of the lower wishbones. This is done to minimise the effects of bump-steer (where suspension movement induces unwanted
sterring effect). Extensions are then fitted to the outer ends of the track rods to restore the overall track width of the modified rack back to
original Sierra dimensions.
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James
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| posted on 1/9/06 at 11:22 AM |
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quote:
Originally posted by nick205
MK narrow the whole steering rack (casing and actual rack). the reason being to bring the inner pivot points of the track rods vertically in-line
with the inner pivot points of the lower wishbones. This is done to minimise the effects of bump-steer (where suspension movement induces unwanted
sterring effect). Extensions are then fitted to the outer ends of the track rods to restore the overall track width of the modified rack back to
original Sierra dimensions.
And also, it should be added, to get the rack mounts *inside* the car! As they're too wide for the car as it is.
Cheers,
James
------------------------------------------------------------------------------------------------------------
"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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mistergrumpy
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| posted on 1/9/06 at 11:24 AM |
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Hmm, Escort rack then, thanks for the tip. Does anyone have any dimensions for the front bones then for the standard chassis with a Sierra De Dion
rear axle. I only ask because I can't get my RHS today because of half day finishing and I seem to have found some tubing in the garage so was
going to have a bash at knocking some up over the weekend. Got an itchy trigger finger 
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nick205
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| posted on 1/9/06 at 11:31 AM |
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 good point james
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StevieB
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| posted on 1/9/06 at 11:41 AM |
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I though the sierra rack casing only was shortened to fit inside the body to make a neat job - oops!
What would be really good would be to find a rack of the right dimensions that has a nice alloy casing, rather than the heavy, rusty beast that the
sierra unit is!
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MikeRJ
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| posted on 1/9/06 at 12:46 PM |
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quote:
Originally posted by StevieB
I though the sierra rack casing only was shortened to fit inside the body to make a neat job - oops!
What would be really good would be to find a rack of the right dimensions that has a nice alloy casing, rather than the heavy, rusty beast that the
sierra unit is!
I have an alloy Sierra rack, I didn't realise they were ever made in iron.
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ecosse
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| posted on 1/9/06 at 12:48 PM |
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quote:
Originally posted by mistergrumpy
Does anyone have any dimensions for the front bones then for the standard chassis with a Sierra De Dion rear axle.
+4 inches (total width) or 2 inches each side on the book dimensions is how I did mine.
Cheers
Alex
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procomp
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| posted on 1/9/06 at 12:55 PM |
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Hi for the standard book front just use a std escort rack with or whithout extensions to suit the whishbones your going to use. Positioning the rack
to suit after will take care of the bumpsteer.
cheers matt
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StevieB
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| posted on 1/9/06 at 01:42 PM |
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My sierra rack is a bit funny - half seems to be allow, but the other half is caked in rust, so obviously ferous. In my opinion, the whole things is
far too heavy for the locost application, it'd be nice to find a lightened casing to use that is the right size for locosts - anyone own a
machine shop that could turn these out?
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nick205
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| posted on 1/9/06 at 01:57 PM |
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All the Sierra steering racks I've seen (PAS and non PAS) have been alloy cased. Are you sure it's off a Sierra?
A good clean with gunk and a stiff brush should bring it up almost like new.
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StevieB
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| posted on 1/9/06 at 02:40 PM |
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My steering rack (and all donor parts) came from MK - the rack was already modified. I'll degrease it and give a good scotchbriting (the best
rust remover and aluminnium cleaner ever invented!) and see how it comes out. Would still be nice to have a lighter unit (does anyone know if the
escort units can be fitted to the MK easily?)
PS - Apologies if I've hijacked the thread, sorry!
 
Rescued attachment Steering Rack and Track Rod Ends.jpg
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mistergrumpy
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| posted on 1/9/06 at 03:21 PM |
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No worries over hi jacking Stevie, I'm soaking all the info up myself.
quote:
2 inches each side on the book dimensions is how I did mine
Ah but is yours a book chassis, says 442 on your avatar don't it. What concerns me is the length though.
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StevieB
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| posted on 1/9/06 at 03:24 PM |
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This is first time I've really looked at my steering rack - I'm fairly sure the two halfs aren't from the same car!
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mistergrumpy
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| posted on 1/9/06 at 03:29 PM |
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Hmm, one of the ball joints looks different to the other don't it. Ones round and ones flared?
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StevieB
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| posted on 1/9/06 at 03:34 PM |
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They're both flared, but on the same side, so obviously both from the same side of two different cars. That's not a problem, because
it'll be new TRE's when I get round to that bit anyway (soon).
What really bothers me is the actual rack casing - I like the principle of less is more, and would really like to get a unit that is smaller and
lighter if possible. I have a friend who's got an original Lotus 7 and he was quite taken aback by how ugly and heavy the sierra stuff really
is - way off the original concept of being quick because there's no unnecessary weight being carried!
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ecosse
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| posted on 1/9/06 at 04:54 PM |
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quote:
2 inches each side on the book dimensions is how I did mine
Ah but is yours a book chassis, says 442 on your avatar don't it. What concerns me is the length though.
442 chassis (which is the same width as book at front), full width sierra axle and +2" added to each bone to compensate for the wider rear
track
Cheers
Alex
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JoelP
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| posted on 1/9/06 at 05:24 PM |
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some sierras had steel racks. I own both!
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StevieB
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| posted on 1/9/06 at 06:48 PM |
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I obviously have half of both!
I was planning on painting it to stop it rusting again - guess I'll have to use a bit of etch primer for the aluminnium part
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nick205
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| posted on 2/9/06 at 11:39 PM |
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Joel - I stand corrected on the steel Sierra rack.
StevieB - If it were me I'd go back to MKa nd get them to supply you a modified rack made of ally left and right halves at the very least. I
think that's a poor effort on their part 
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