Read an article in a popular mag entitled 'diss Torsion' about fabbin' a torsion bar suspension for a trad beam axle-split bones setup. Got to liking the idea so I went to the Schroeder pages and printed off all the charts listing their torsion bars by the various lengths subdivided by the various diameters available for each bar. After spending a half hour or so trying to nail down just which bar would be right for my app., I began to notice that the exact specs for say a 30" bar at 7/8" dia. and using a 10" torsion arm could also be found on the chart for a 28" bar at 7/8" dia. using a 10" arm. I looked a little more and found that the specs for any length bar could be found on the chart for any other length bar. I went back to the article that I read in the first place and they show two of the actual Schroeder charts in the article. Sure enough you could find the same specs line that they highlighted on one chart also on the other chart! So I went ahead and emailed two of the tech editors asking them about this...no answer. I emailed the mag's open forum...no answer. I tried Schroeder...no answer. Now I'm putting the question on the H.A.M.B. to see if anyone knows how to decipher these charts or how someone decides which is the correct bar length for a given app. Am I missing something that's painfully obvious or is this some kind of hot rod voodoo? Youth and enthusiasm is no match for old age and treachery!
I got a set up done by a roundy guy in denver back in the late 60,s early 70,s on my beam frt 59 mopar drag car heavy but cool it,s f100 with cross torsion and coil over well engineered but heavy all stick welded and STRONG!!! I,ll see if I can get some pics its on the hoist now
This is the http://www.streetrodderweb.com/tech/0902sr_putting_torsion_bars_on_a_hot_rod/index.htmllink to the mag article
I'm still hoping someone has the answer to my original post.(below) The mag article is at http://www.streetrodderweb.com/tech/...rod/index.html and all the charts are at www.Schroedertorsionbars.com
Magazines rarely give enough information, on any subject. The first 9 charts on this page: http://www.schroedertorsionbars.com/OWbarsPage.html are part numbers based on outside diameter and overall length. For example: # 225SD725 = 7/8" od, 22.5" long, solid , .750 working dia. #29GD750 = 1 1/8" OD,29" long, hollow, .750 working dia. # 30GD750 = 7/8" od, 30" long, hollow, 750 working dia. All step down to the same working diameter, but are different lengths, with different diameter splined ends. These charts: http://www.schroedertorsionbars.com/TorsionBarChartPg-Nu07.html give you the spring rate based on bar size and the torsion arm length. First axample above: # 225SD725 = 7/8" od, 22.5" long, solid , .750 working dia. Look on this page: http://www.schroedertorsionbars.com/TrsionBarRate-07PDFs/78SH225.pdf Effective bar length 18.5" 9" arm-> 238.4 lbs/in 12 arm-> 152.9 15"arm-> 85.8 Third example above: # 30GD750 = 7/8" od, 30" long, hollow, 750 working dia. Look on this page: http://www.schroedertorsionbars.com/TrsionBarRate-07PDFs/118SGD30.pdf Effective length 24". 9" arm-> 183.8 lbs/in 12" arm-> 103.4 15" arm-> 66.1
The first number, is the size of the splines. 3/4", 7/8", 1", 1 1/8". They come in straight and tapered. http://www.schroedertorsionbars.com/OWarms.html This is also the size of bushings used in the frame. Most bars step down smaller in the middle, to what I refer to as the working diameter. Calculations are based on the length of this working diameter, not the overall length.
Obviously WAY over their heads. They just publish what they are given, maybe edit for spelling and sentence structure.
Once you design your suspension for a given dia and length bar, then you can substitute different "working diameter" bars to get the wheel rates close to what you need. Then fine tune with arm length. Plan ahead, some sizes offer for options than others. eg: 7/8 x 28" goes from .400" to 1.000" With a 12" arm, that goes from 8.36 lbs/in to 326.7 lbs/in. Should cover almost anything. Personally, I'd try to use the same dim bars, front and rear. Just change the working dia to get the wheel rate. For the street, I'd stick to solid bars. Hollow bars are for serious racing, but don't last as long.
Check the top of each chart: 7/8" x 28" bar has a 24" effective length. 1" x 28" bar has a 24" effective length. 1 1/8" x 30 bar has a 24" effective length. So even when the size of the ends are different, the working diameter and length are the same. So with the same working diameter, effective length, and arm, the rates will be the same.
The Jalopy Journal
