a pics of trailer arm i build
- Thread starter sweetv6
- Start date
- Joined
- May 28, 2001
What's behind the idea of having all that threaded shaft sticking out??
- Joined
- May 28, 2001
That's the..
?.....
Bending stresses are going to show at the weak link. That threaded rod is the weak link.
??
?.....
Bending stresses are going to show at the weak link. That threaded rod is the weak link.
i dont think the rear end can broken, twins or bent a
3/4 grad 8 ( 56 000 psi ) threaded or not lolol
a screen shot of the ajustable one
Claude
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- Joined
- May 28, 2001
"3/4 grad 8 ( 56 000 psi ) threaded or not "
Whatever...
Whatever...
As a Mechanical Engineer I can appreciate that there are "stress risers" at the point where thread meets the shank of the rod end... and that is likely where the weak link is.... however since I haven't modeled it myself... it is hard to say if it will or won't be a problem.... You would have to assume some load to model it accurately... and it would be a "guess" IMHO.... without some data from an arm fitted with strain gauges and run through some testing where you load the crap out of it...
With that said... it is entirely possible that the size of the rod end... is plenty big and will never fail.... but who knows???
I hope SweetV6 has made his based off of either a similiar commercially available part... or assumed loads that are worse than it will likely see... and designed accordingly...
In any case... the solid model looks sweet.
Can we see the FEA output screenshot? .... and what loads did you assume?
The upper control arm is in tension on a launch so the threaded part will probably be okay, it's just a question of how many miles to pound out the rod end and if it's a race car that may take forever. The lower arm is under compression, however, and for a short column (I used 3/4" solid round x 4" vs. 2"x1.5"x0.125" wall x 4" as a guesstimate of the tube size to make a quantitative comparison) the rectangular tube can carry just under twice the load of the 3/4" solid round. Going up to 1" solid rod gets you back up to almost the tube strength (1300 lbs for the 3/4", 2600 lbs for the 1", and 2800 lbs for the tube), but in reality this is ignoring the thread depth so you really should go to 1-1/8" threaded rod to roughly equal the tubing as a column.
Basically, but with a column slenderness ratio of about 7-10 it should fail by direct compression, not buckling. I used a couple of different formulas built into an engineering program I have that include some empirical corrections based on the slenderness ratio (American Institute of Steel Construction and American Railway Engineers Association formulas if you care), instead of digging out the formulas and doing it by hand. This ignores the rest of the length of the control arm, and ignores any bending going on from binding bushings (where the smaller diameter compared to the rest of the control arm will really make it look bad), but I just wanted to get a feel for what size threaded rod would give a comparable column strength to my guess at the tubular control arm dimensions, since I "know" that they work and I don't know what the columnar load actually is in pounds . Go to Mechanical Engineering Software - Engineering Power Tools and get the freeware version of engineering power tools. It's really useful, and the full version is even better at a really decent price. I don't think the freeware one has the column and plate calculations, and it has fewer beam deflection geometries to choose from, but it is still good.
. Go to Mechanical Engineering Software - Engineering Power Tools and get the freeware version of engineering power tools. It's really useful, and the full version is even better at a really decent price. I don't think the freeware one has the column and plate calculations, and it has fewer beam deflection geometries to choose from, but it is still good.
- Joined
- May 28, 2001
On a comparative basis, those long bolts are waaay longer than any aftermkt arm I've seen, that uses a heim.
This includes 4 links, ladder bars, Caltracs, etc. Most all I've ever installed, had instructions that called for minimal thread exposure. Furthermore, all the systems I've used have all had male heims.
There's significant bending stress incurred when lifting the ft end of a 3700# GN. When we made our own bars, we used stresscoat, to see what was going on....
This includes 4 links, ladder bars, Caltracs, etc. Most all I've ever installed, had instructions that called for minimal thread exposure. Furthermore, all the systems I've used have all had male heims.
There's significant bending stress incurred when lifting the ft end of a 3700# GN. When we made our own bars, we used stresscoat, to see what was going on....
Hi guy
i based my arm design on pics att.
I had a comment from 2 mecanical engineer prof. and
it's ok for them. I think the arm should see only
tension and compression too. if the fissuration can
start in my threaded rod or if it is a weak spot
take a look on pics att. btw yes it is a guess design.
the 4 black arm on tile are under louis lopez's
car if my memory serve me well
the other are a commercial arm.
---------Can we see the FEA output screenshot? .... and what loads did you assume ?
i dont know FEA output may be the finishing element analysis
the load i assuming is the section of a tube 2" x 2" 0.100 Th 50W ( like we can see on commercial arm )
the limit of the rod is 3.1416 x .375 x .375 x 56 000 psi = 24 740 lbs, tube have .75" sec. area x 50 000 psi = 37 500 lbs
the maximum load on the rod end is 10 500 lbs it is the weak spot of the montage. there is why i think is ok
Claude
i based my arm design on pics att.
I had a comment from 2 mecanical engineer prof. and
it's ok for them. I think the arm should see only
tension and compression too. if the fissuration can
start in my threaded rod or if it is a weak spot
take a look on pics att. btw yes it is a guess design.
the 4 black arm on tile are under louis lopez's
car if my memory serve me well
the other are a commercial arm.
---------Can we see the FEA output screenshot? .... and what loads did you assume ?
i dont know FEA output may be the finishing element analysis
the load i assuming is the section of a tube 2" x 2" 0.100 Th 50W ( like we can see on commercial arm )
the limit of the rod is 3.1416 x .375 x .375 x 56 000 psi = 24 740 lbs, tube have .75" sec. area x 50 000 psi = 37 500 lbs
the maximum load on the rod end is 10 500 lbs it is the weak spot of the montage. there is why i think is ok
Claude
Attachments
And on all of those lowers the exposed length of thread is much shorter. I don't KNOW that yours are too weak because I don't know how strong they really need to be, I just wanted to point out that the threaded portion of your lower arms is only about 1/2 as strong as the tubular section it replaces.
imjoesnuffy
I just break stuff!
- Joined
- Sep 13, 2005
yes it's umi
but if you looking for a arms go with h & r parts and stuff
HRpartsNstuff "Your WWW performance parts supplier"
talk to Paul
imo
Claude
toofastforyou
2FAST4U
- Joined
- May 25, 2001
H&r...
I have the whole H&R setup on my car (adjustable upper and non adjustable lower control arms + sway bar) and I'm very happy with them, although I've not really begun yet to "fine tune" the suspension for better launches. I've also added QA1 shocks...
Claude :smile:
I have the whole H&R setup on my car (adjustable upper and non adjustable lower control arms + sway bar) and I'm very happy with them, although I've not really begun yet to "fine tune" the suspension for better launches. I've also added QA1 shocks...
Claude :smile:
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