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About to do something crazy... (adding 12" rear suspension)
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Author:  rifleman [ Mon Jun 22, 2009 12:28 pm ]
Post subject:  About to do something crazy... (adding 12" rear suspension)
Hello! Nice forum here, thanks to the guy who posted the link on dune-buggy.com when it went down.

I posted this over on samba but thought I'd get some input over here as well:

Currently I've got a IRS rear with boxed in arms on a medium weight buggy. I'm looking to add 12in of travel (17" total) which with my current swing angle (33.5*) I'll need to fabricate 13" longer arms--I may go about 4" inches wider (I'm a bit limited b/c of my trailer)

I'll be running 7100 18" Bilstiens with reseviors and big fat torsion bars (not sure of the diameter, but they're as wide as the splines)

For the trailing arm pivots I'll be moving to a heavy duty helm joint.

And for the CV's, I'll be fabricating a custom rig utilizing pto universal joints. I realize I'll get some pulsation, but I'll be offroad and at least I'll have 17" of travel

I'll be moving the engine/trans back accordingly as well.


Autocad .jpg here: http://images.thesamba.com/vw/gallery/pix/568569.jpg
edit - I was playing around with using 930's when I drew this up. I doubt these dimensions would work-I would think you'd need the distance between flanges just over 18.75 based on the cv dimensions.
Image







Your thoughts?



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Author:  MickeyMouse [ Mon Jun 22, 2009 12:45 pm ]
Post subject:  Re: About to do something crazy... (adding 12" rear suspension)
Hey Rifleman,

Welcome to the forum.. There are great guys on here with TONS of knowledge. The Samba is nice but if you need Off Road advice, this is the place to be..

As for your post, I am a bit confused.. I understand that you want 17 inches of travel but why do you need 13 inch longer arms? Do you really only have 5 inches of travel today?

At the end of the day, you are on the right track, 2x3 or 3x3 arms will get you the travel you are looking for. 930 CVs should be able to handle the angle with no problem. You do not need to calculate the entire swing angle, just the angle from the horizontal.
Author:  rifleman [ Mon Jun 22, 2009 6:28 pm ]
Post subject:  Re: About to do something crazy... (adding 12" rear suspension)
Yep, only 5" in the rear right now because of some stops I welded in to save the shocks--But I've upgraded shocks so the stops will come out (giving me that 34deg angle).

I may notch the spring plates to increase the angle and then the arms won't have to be so long. I know they'll be alot of stress on the torsion bar splines--is it possible to weld them in or maybe drill and use a grade 8 bolt without taking away their strength?

edit- I know I've seen a 3d solid modeling file of the stock torsion arms somewhere on the net (maybe BCR?) but I can't find it anywhere. Does anyone have this? Autocad would work too.


thanks,
adam
Author:  RaceBugg1098 [ Wed Jul 01, 2009 10:11 am ]
Post subject:  Re: About to do something crazy... (adding 12" rear suspension)
Welcome, rifleman! I'm all about long trailing arms, but 13" over is a little much. The arms I built for my race car are about 10" longer than stock and 9" wider per side. That is about as long as you want to go without major engineering. I think if I wanted to go longer, I would actually loose travel. Right now I'm getting just under 21" of usable travel with a max cv angle of around 22*. The trans is 4" back from the "stock" location. Look at june of '08 BOTM for pics. Another thing to keep in mind, you gain travel quicker by going wider than by going longer. The longer you can make that axle, the more travel you can get, and longer axles will "wrap" acting like a shock for your trans.
Author:  Dave Winterburn [ Wed Jul 15, 2009 12:56 am ]
Post subject:  Re: About to do something crazy... (adding 12" rear suspension)
I'm right cofused, "Big fat torsion bars" and hiem joint spring plate ends? Did you mean axels instead of torsion bars?
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