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  #81  
Old 01-04-2013, 03:28 AM
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deaner deaner is offline
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i hate to say it ,but i think you will have toe problems, bump steer, in the back also. as the bottom a-arm travels up and down, the angle of the a-arm to the upright changes. this changes the distance from the upright to the mounting point you used on the a-arm. the track arm/tie rod has to be mounted to the frame on the inboard end, and parallel to the bottom a-arm.
as for the front, the tie rod length needs to be a happy medium between the lower (longer) and the upper (shorter) a-arms. also happy medium as far as parallel to either arm unless the upper and lower a-arms are parallel. the inner pivot of the of the tie rod will end up toward the wheel because the outer end is out (closer to the rotor) to get full akerman angle. if you use a r&p box with a center load, you can use a spreader bar to get the inner tie rod mounts out to where you need them.(but if the spreader bar needs to be too long it will put too much stress on the center load r&p)
mounting the a-arms higher in the front works okay, but there are some things to consider. mounting them at say 10 degrees allows you to keep your a-arms the same shape and position to give you a 10 degree kingpin inclination,which is needed to keep the car straight without a fight. it also keeps things simply and neat, but when your wheel travels up or down it goes forward and back, which changes the geometry and can lead to bump steer. bump steer is very hard to eliminate with unequal length a-arms. Equal length a-arms give you better bump steer characteristics, but terrible camber change in corners as the body rolls.
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  #82  
Old 01-04-2013, 05:23 AM
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.

Last edited by Redliner; 01-12-2013 at 08:32 PM.
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  #83  
Old 01-04-2013, 09:10 AM
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350 Vortec 350 Vortec is offline
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Well you can race with no suspension at all if you wish-just wont get on so well.
Having taken a closer look through vids again i actually doubt you'll have what i would call long travel up front anyway-then long travel can be a matter of opinion
Again in my opinion Your rear track rod wishbone bracket's are not up to the job...and sack Mr mig (if you paid him)
Of course as you say-all weak points will be found when you start testing but obvious ones should be sorted beforehand to at least save possible knockon damage,we all have opinions and things we are good at-a little from everyone can make you a winner
It's a great project and i as with most i'm sure want to see you win in it!!
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  #84  
Old 01-04-2013, 12:50 PM
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If your rear upright stays vertical as it goes up and the lower a-arm goes up on the outside, won't the inner part of the a-arm (where the tie rod is mounted) get farther from the upright? I've seen this done on purpose to steer the rear slightly as the body rolls in a turn, but this was on flat track with very little suspension travel.
On the front, ackermann angle will increase as the r&p (or idler arms) are moved to the rear of the car, and decreased as r&p moved toward front.
Thanks for putting yourself out there, this is a great build to watch!
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  #85  
Old 01-04-2013, 02:18 PM
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350 Vortec 350 Vortec is offline
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Yes your right deaner,the rear will steer as it cycles,never thought of it before
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  #86  
Old 01-04-2013, 03:07 PM
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I understand the complexity of designing around 'yard parts' a new suspension design and the frustrations there of.
It is not like modifying a factory design where you are constrained to a fairly well defined envelope and so can not eeF-it up to badly. Start from scratch and suddenly what looks like a simple project of connect the dots turns into a quagmire where everything effects everything and more often then not in a negative way! It is therefor understandable that when a bunch of us webexperts chime in pointing out this or that, it sounds like negative criticism. Which it may be, though on the OFN it is intended as positive input, I shall not speak for other places.
I'll stay out of critiquing your design anymore then I have it, reads on this end like you have had enough of that. I am going to make a suggestion that may save you time. Build your front suspension out of ABS or PVC plumbing pipe (even wood) between your pivots and only tack the pivot points so that you can take them off and move them. You can then simply and quickly build full scale models of your ideas and then actually cycle them and watch the actual movement that you intend and what you didn't (IF that even happens).
I enjoy each installment, I'm pulling for ya
E
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  #87  
Old 01-04-2013, 05:54 PM
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Thanks guys. Entropy the whole front end is only tacked for that very reason.
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  #88  
Old 01-04-2013, 11:55 PM
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i agree with E. After drawing everything out, I mocked mine up with pvc. You can tap 3/4 pvc with a tap or just thread in a 3/4 rod end (fast, easy,cheap) I spent six hours trying to get everything right on mine after thinking I had it right on paper. Then after tacking it up, I still had to move the r&p back to get proper ackermann. It can be very frustrating. Hopefully we can pass on some of this information to make it easier for you and the readers.
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  #89  
Old 01-05-2013, 12:12 AM
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Quote:
Originally Posted by Redliner View Post
Part 5 video - Front suspension mounts & rear brakes

http://www.youtube.com/watch?v=aH6EEjzmOYM
At 2:09 of your video, you've got the spindle upside down, you have the left side spindle on the right side of the buggy...
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  #90  
Old 01-07-2013, 11:32 AM
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Any progress? Maybe pics of pvc a-arms?
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  #91  
Old 01-08-2013, 08:03 AM
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Part 6 - Fabricating the Front Wishbones

http://www.youtube.com/watch?v=pMu-606UUPU
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  #92  
Old 01-08-2013, 12:30 PM
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alwaysFlOoReD alwaysFlOoReD is offline
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I got a chuckle out of the first part of your vid.

Richard

Last edited by alwaysFlOoReD; 01-13-2013 at 04:05 AM.
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  #93  
Old 01-08-2013, 05:39 PM
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TBH Making little of ppl with good advice and intentions here is how it sound's to me..................
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  #94  
Old 01-09-2013, 12:55 AM
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Whats the scrub radius with the uprights upside down?
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  #95  
Old 01-09-2013, 01:01 AM
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What's the camber at full drupe? Oh ya, you can't measure that with the frame screwed to the table.
What's the camber at ride height? Oh ya you can't measure that with the frame screwed to the table.
Well the camber is probably okay cause its set at 1 degree at full compression. LOL
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  #96  
Old 01-09-2013, 01:03 AM
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Are the a-arms equal length with the upright upside down, or is the top one longer? LOL
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  #97  
Old 01-09-2013, 08:13 PM
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Redliner,

It looks like you are better at engineering than re-engineering, so why don't you build your own uprights?
You can make them lighter with everything in the correct place for your car.
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  #98  
Old 01-10-2013, 11:35 PM
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Deaner all those measurements will be checked after the wishbones are tacked. Then the car will be pulled forward so the arms CAN be tested through their travel range. This is only a first tack up.

I don't mind being wrong, and I appreciate advice from those who have actual build experience before me. But that can be delivered in a constructive or a smart arse way & I just don't need negative attitudes & criticism in my life, or people presuming I am unaware of what I may not yet have included in my build videos.

You guys need to remember I am stretching myself in building something totally new both to me and most other racers, and that there ARE no earlier builds for me to follow on this whole project. To those critical of me I would ask - just exactly how many fwd to mid-engined buggies have you built?

I really don't like the tone of some of the responses I'm getting here of late, and am very close to just pulling this whole thread.

Last edited by Redliner; 01-10-2013 at 11:53 PM.
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  #99  
Old 01-11-2013, 08:51 AM
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12husky 12husky is offline
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I have been watching silently and enjoying every part of the build so far. I am currently building a small buggy using a stock VW front end and a Mazda RX7 rear. My build is using all stock components to get me some more experience before I try one with custom suspensions like yours. I have been keeping my eyes out for a donor such as yours to start the next one from.

I guess what I am saying is, please don't pull your thread as there are those of us watching to learn from what you are doing so we can apply it to our own projects.

Thanks and good luck!
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  #100  
Old 01-11-2013, 11:18 PM
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Redliner, In my first post I tried to give enough info so others might be able to understand what I was talking about. I think you took that the wrong way.
SteveL was nice about telling you your upright was upside down in the video.
If you put a straight edge on your back hub and point it toward the front, then lift the hub to full compression and see where it points. That will indicate bump steer if there is any. A video of this would be great so we all could learn something.
I've been interested in this thread because I have been fabben for a long time and built a sand car last year using a GM fwd eng/trans in the rear. I fabbed up all four uprights and two a-arms on each corner with 20-22 inches of travel.
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