James,
Thanks for the reply. The upper arms wouldn't have to be
considerably "longer", per say (or at least there length projected
against the horizon wouldn't have to be longer (go tell your old math
teacher, we're using Cosines in real life!!!)), but their mounting point
on the x-member would have to be lowered. I understand that most
kit-manufacturers would like to use stock mounting points and therefore
make a bracket that mounts to where the old Armstrong shock would
attach, but many of those kits also require you to cut the ends off the
x-mount so that the coil-over could fit. That being said, it shouldn't
be too much harder to mount the upper A-arm pivot-points lower on the
x-member. Ideally, I'd like to buy a post 74 x-member and some mustang
II parts and just muck around until I get a decent geometry. There are
some relatively cheap design packages for PC out there, too. One can
use them to find roll-center, etc. With a little inspiration, we could
also build in some anti-dive on the front end.
I've done some welding (even took a course once), but I wonder if I
would have to do any fancy heat-treating (stress relieving if I made any
of the new linkages? Thoughts from anyone??? I promise I won't hold
anyone liable for their welding advice if one of my a-arms flys off at
65 mph ;-)
James J.
james wrote:
>James, that is an interesting observation. I'd certainly be interested in
>anything that you find out. I haven't put a lot of work into suspension
>design because I've never really been at a point to do it all over. It is
>something I plan to do but not for a few years. I can, however, offer you
>two things. One, I have been told that the negative camber a-arms don't
>adversely effect tire wear if you are a spirited driver. Two, a whole lot
>of things get built but few ever really get designed. I think that the
>intention of many of the kits is to move the shocking and springing into the
>modern era with coil overs or with tube shocks. I would also guess that
>people have shied away from complete redesign because of development cost
>versus saleable cost and quantity.
>
>I suspect that one of the problems in making the upper a-arms longer then
>the lowers is the shape of the body. I think that in order to make the
>upper a-arms substantially longer, they would have to be mounted on the
>other side of the inner fender, perhaps on the frame rail. Just a couple of
>things off the top of my head.
>
>James Nazarian
>71 B tourer
>71 BGT V8
>85 Dodge Ram
>----- Original Message -----
>From: James J. <m1garand@speakeasy.net>
>To: <mgb-v8@autox.team.net>
>Sent: 26 January, 2003 7:25 PM
>Subject: test, e-mail notice, and suspension question
>
>
>
>
>>First, to my DC area friends, my e-mail is now m1garand@speakeasy.net
>>now that DirecTV has shut down their DSL service.
>>
>>Now to the group: (and answer me directly if you think it is off-topic
>>enough that the group wouldn't be interested) I've been reading up on
>>suspension design, primarily to see about options for the back-end, but
>>I also started looking at front-end design. What I noticed, is that
>>every author that I read said that un-even length, non-parallel a-arms
>>are the way to go in nearly evey case (so far, so good, for the MGB),
>>however they all suggest that the upper a-arm should be higher at the
>>wheel than at the cross-member. The reason being that when a car rolls
>>to the right (for example) the wheel on the right side also leans to the
>>right, reducing the size of the tire contact patch. With the MGB, as
>>that side of the suspension compresses, the upper a-arm travels up
>>through it's arc, becoming longer relative to the hub, pushing the top
>>of the wheel even further out and reducing the tire contact patch even
>>more. If the upper a-arm (in its static position) was angled upward
>>from the x-member to the king-pin, then any roll to that side would
>>compress the suspension and make the upper arm SHORTER relative to the
>>lower arm, and bring the top of the tire back in to reduce the camber
>>effect of the roll, and increase the size of the tire contact patch,
>>improving handling.
>>
>>First, I wonder what the MG guys were trying to achieve with that
>>design, and second, I've seen at least four new coil-over designs for
>>the MGB, where the old a-arms are dismissed with, yet none of them
>>change the geometry to "fix" the upper a-arm issue. The car can be
>>designed with some built-in static camber to compensate for this, but
>>that method increases uneven tire wear on the inside edge. Has anyone
>>here used a front-end design that corrects the camber issue? Most of
>>the kit/muscle/street-rod crowd have adopted the Mustang II front-end,
>>and the parts for this are plentiful and relatively cheap (Including 2"
>>dropped spindles). (remember that this car was the same platform as the
>>Pinto/Bobcat.......Kaboom!!!!!)
>>
>>So if anyone has any experience, I'd love to hear from them. Also, if
>>anyone is interested in working with me in trying to adapt the mustang
>>II front end to the MGB, let me know. When things get a little quieter
>>around my house this spring, I want to start taking dimensions off the
>>MGB for the front-end and back end and putting them into CAD, and
>>playing around with them. TurboCAD is cheap and powerfull. If anyone
>>has done something similar, and would like to share their files, please
>>let me know, too.
>>
>>Thanks, and my apollogies to those who don't want to read about
>>suspension design.
>>James J.
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