Rob
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May 21, 2007 20:26:11 GMT
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Hey again.... I have recently been looking at different front ends for the Marina. I think the only piece getting in the way of a decent engine position is the steering rack (which is mounted above the trans tunnel on the firewall) With this moved I can move the engine back and up those vital inches. So... I'm prepared for lectures on steering geometry . . . It is currently like this :: Now circled in green - could it be moved to either place in red ? (obv it would require fabrication) but could it keep the geom? if the distance / arc of the arm remained the same ?  |
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May 21, 2007 20:30:51 GMT
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we managed to get a pinto in without too much trouble, notched the top of the bellhousing for clearance and it is all OK, doubt you could get it much further back without modding the bulkhead.
You need to have a good look at the steering geometry before you move it, remember the geometry might not be ideal to start with!
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Rob
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May 21, 2007 20:36:21 GMT
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I have no issues with chopping the trans tunnel - the only bit that concerns me is the geometry - I'm sure there is much more I SHOULD be concerned with !?  |
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paulw
Part of things
Posts: 217
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May 21, 2007 20:52:12 GMT
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The chances are that you'd end up needing a rack of a different length. If you imagine a line drawn between the inner pivot points of the top and bottom susp wishbones/links, then the inner pivot points of the steering arms at each end of the rack will need to be roughly in line with those and parallel to the suspension links. This is a bit of a simplification but you can see that since the suspension probably has longer links on the bottom you'd need a different length rack to get this sorted. Plus you've got all the fabricating of the steering arms, which not only have to be strong but shaped to put the steering forces directly through them with no twisting or deflection. There's some shocking conversions for sale in the states that have all sorts of bodged steering arms spacers and extensions that I wouldn't trust to the end of the road... It's not going to be easy - it can be done, but needs plenty of sums doing before you start  |
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Lotus Seven
'58 Ford Special
64 Barracuda
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Rob
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May 21, 2007 21:15:22 GMT
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Cheers Paul - excellent answers. Anyone have any sites with drawings on em ? Re fab - I have John Sleath local to me so would be consulting him on this... I know what he'll say tho.. "rip it out, spaceframe it, and bolt up a viva unit or fabbed a arms" He's such a pro... |
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v8ade
Part of things
Posts: 947
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May 21, 2007 21:24:23 GMT
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V8 on open headers at full throttle "Heaven"
Jaguar xf SportBrake
rover 820 Turbo vitesse
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v8ade
Part of things
Posts: 947
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May 21, 2007 21:28:05 GMT
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V8 on open headers at full throttle "Heaven"
Jaguar xf SportBrake
rover 820 Turbo vitesse
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Rob
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May 21, 2007 21:38:38 GMT
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Cheers Ade - they're excellent ! PS: anyone got a viva front end for sale ?  no - seriously... |
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Last Edit: May 21, 2007 21:51:55 GMT by Rob
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stealthstylz
Club Retro Rides Member
Posts: 14,959
Club RR Member Number: 174
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May 21, 2007 21:52:20 GMT
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Keep the rack rearmounted will make it easier to calculate the ackerman angle etc
Matt
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Rob
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May 21, 2007 22:05:11 GMT
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Looking from above - directly down on the king pin.
If I move the steering arm (how will come later) to a point directly vertical / plumb from the point it's currently at - would that keep it ?
ah... will it change depending on the kingpin castor angle ?
Am I getting this ?
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Dez
Club Retro Rides Member
And I won't sit down. And I won't shut up. And most of all I will not grow up.
Posts: 11,790
Club RR Member Number: 34
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May 21, 2007 23:03:03 GMT
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looking at that, you should be able to moove the rack straight down and it'll handle exactly the same. keeping it behind the hubs is definately the best option.
post a pic of the backside of your discs/caliper/stubaxle arragement so we car see the scope for new mounts.
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rod
Posted a lot
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You gotta also watch the relationship of rack steering arm pivot point to the pivot point of the bottom susp arm . I put a rack on my A40 Farina from a Mini ...It bumpsteered all over the place ! Have seen bellhousings notched in the past ..think as long as you don't go too deep ,and radius all the corners to minimise stress points it should be OK .......Just my 2p........
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Last Edit: May 22, 2007 5:22:44 GMT by rod
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I'd be looking at looking at swapping a whole front clip in from a Viva or some other car which uses a double wishbone setup. Rack retains its relationship to everything then as you use the one off the clip donor.
A Chevette might by aboiut the right width.
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Last Edit: May 22, 2007 8:00:40 GMT by akku
1941 Wolseley Not Rod - 1956 Humber Hawk - 1957 Daimler Conquest - 1966 Buick LeSabre - 1968 Plymouth Sport Fury - 1968 Ford Galaxie - 1969 Ford Country Squire - 1969 Mercury Marquis - 1970 Morris Minor - 1970 Buick Skylark - 1970 Ford Galaxie - 1971 Ford Galaxie - 1976 Continental Mark IV - 1976 Ford Capri - 1994 Ford Fiesta
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Rob
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I think you might be right Alistair... BUT. Just for those who may be interested. My front suspension set up. (Cheers Dez by the way)    |
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John
Part of things
Posts: 347
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May 22, 2007 16:51:24 GMT
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You can mount the rack anywhere you like and get no bumpsteer (or minimal in the range of suspension travel that matters). However the chances are you will have to alter the length of the rack, that is pivot to pivot.
For bumpsteer the position of the pivot is critical. As has been explained before there are ways to find the correct rack length.
The easiest way to avoid bumpsteer is to build a replica of the suspension from card, ply etc. have pins at the pivots of the wishbones, a dummy upright etc. Then you can move the suspension up and down. Try putting a steering rack in different places with a steering arm and moving it up and down.
Ackerman is easy in comparision. Just make sure a line from the track rod end to upright points to the centre of the diff ( or close).
If you move your steering rack and arms straight up then the rack will require shortening.
You could swop the uprights left to right and swop the steering arms round and get a front mounted rack but this will mean the engine a long way back to clear the front of the motor. You may find theres a woodruff key on the steering arm, leave it out and 638 Loctite the arm in.
However this is how I would do it. (We had this same issue when messing with Minors and I could never come up with a solution, but now I just seem to have so many more ideas........)
Mount the rack low and at the front. Use the 4 bolts that mount the caliper to attach a steering arm. You will have to fabricate a steering arm that bolts on and make sure it will not fatique. Then you will have to get a rack the correct length.
Shortening A Rack....... This is fortunately quite easy. Where the track rod pivot is there is normally an external thread and some bores in the end. A machine shop can easily replicate these. The casing is easy.
I hope this helps,
John
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May 22, 2007 18:08:51 GMT
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Nice challenge I've been through all this when I ditched the firewall mounted steering box on the Celica and dropped in a front mounted rack. It does seem a bit daunting to begin with, but its only pivot points, and once you can figure out how they all work and interact together it's not to tricky. Biggest problem I found was mounting the rack where it needed to be without compromising anything. Spent a fair few hours measuring racks and even bought a fair few scrap racks just to experiment with. Ended up with a Volvo 240 manual rack, all hooked up with Flaming River UJ's and shafts.  The only custom part I needed was the steering arm to correct the ackerman angle:  Would I do it again? Would I f##k. Not much help I know, but it shows with a bit of homework and experimentation it can be done. |
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stealthstylz
Club Retro Rides Member
Posts: 14,959
Club RR Member Number: 174
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May 22, 2007 18:33:37 GMT
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Is the steering ok like that the uj angles look a bit sharp unless its just the pic
Matt
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May 22, 2007 18:57:20 GMT
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Probably the photo. It's an early shot (it's all hidden by the engine now) so I doubt I'd set the opearting angle correctly then. All the joint angles are adjustable by the height and position of rose joint support bearings. The top joint is a double UJ  Will accomodate up to 60 degrees. The one on the rack is a single joint and limited to 30 degrees. |
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trevd
Part of things
Posts: 51
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May 22, 2007 19:06:35 GMT
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the ackerman angle needs to be correct , this is probably the most vital thing to consider , as said before , draw a line between the diff and the ball joint pivot point ,(this can extend forwards) if the track rod ends lie on this line it will handle ok , as for bump stear thats the easy one , if you look at the suspension from the front, with the steering straight ahead, the steering rack pivots need to be in line with the inner pivot of the A arms (a little more dificult to calculate if using struts). if you have any problems let me know , i can fabricate parts to suit
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too much is never enough
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Rob
Posted a lot
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Posts: 2,515
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May 22, 2007 21:21:20 GMT
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excellent all round ! I really appreciate people helping (i bullied john up here ! thanks;))
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no - seriously...
