Check out my custom torque arm!
06-15-2004, 09:43 PM
#1
Launching!
Thread Starter
Check out my custom torque arm! These are some pictures of the torque arm I made for my car this winter. As you can see, its tunnel-mounted and adjustable. After looking around at some of the torque arms out there, I realized that I could make my own using the resources we have at work. I also did some engineering work on the various parts and found some very interesting results in the process. Check out the pics and let me know what you think. If anybody's interested, I can explain all the specs and how and why I did it this way, as well as some of the interesting things I found from my engineering analysis. Just ask whatever you want, because I could write a ton on it, but won't unless you guys are curious.
The pictures show it only tacked together because I didn't want to trust my welding. One of my buddys at work welded it up solid later. Unfortunately, I don't have pictures of it mounted because these pictures were taken with my brother's girlfriend's camera, and they have since broken up. It fits like a glove, though, with no fitment issues at all.
Thanks for looking,
Chris
The pictures show it only tacked together because I didn't want to trust my welding. One of my buddys at work welded it up solid later. Unfortunately, I don't have pictures of it mounted because these pictures were taken with my brother's girlfriend's camera, and they have since broken up. It fits like a glove, though, with no fitment issues at all.
Thanks for looking,
Chris
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Wahab Affat (11-29-2019)
06-15-2004, 11:10 PM
#3
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looks nice. since you are already there, i would go ahead and install a driveshaft loop on that crossmember. it looks like you got everything to do it and you will eventually need it anyway.
06-15-2004, 11:46 PM
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At first glance it doesn't look like anything special. Looks are deceiving. That thing looks great.
And who cares about how it actually looks, it's underneath the car. Go test it out.
Hey, if it works good...I'm in the market for a tq arm.
And who cares about how it actually looks, it's underneath the car. Go test it out.
Hey, if it works good...I'm in the market for a tq arm.
06-16-2004, 08:15 AM
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Originally Posted by jd13
At first glance it doesn't look like anything special. Looks are deceiving. That thing looks great.
And who cares about how it actually looks, it's underneath the car. Go test it out.
Hey, if it works good...I'm in the market for a tq arm.
And who cares about how it actually looks, it's underneath the car. Go test it out.
Hey, if it works good...I'm in the market for a tq arm.
A+ job for hand made.
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06-16-2004, 04:34 PM
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It looks very well made to me. Nice job!
Looking at the rod ends, Did you weld nuts to the tubing or have the tubing threaded for the rod ends?
I am very interested in hearing a lot more detail on how you constructed it!
Steve
I can explain all the specs and how and why I did it this way, as well as some of the interesting things I found from my engineering analysis.
I am very interested in hearing a lot more detail on how you constructed it!
Steve
06-16-2004, 06:52 PM
#9
It is refreshing to see folks design components for their cars. There is a self gratifiying feeling that cannot be replaced.
Some constructive criticism for your design...no disrept whatsoever. Below are some considerations you may have overlooked.
1) From an engineering stanpoint, using two "truss's" running parallel with perpindicular connecting points is an inferior design to a triangulated construction. A trianglulated design will prove to be stronger and distribute the load better.
2) Higher HP setups will bend the floor panels with the front connection points your using. A more appropriate design is to tie the connection points into your subs for example.
3) The front brace you may end up bending that also...not certain of your wall thickness as well as the grade steel used.
Though i'm pointing out some of the negative aspects, overall, a good job and you should be proud of your accomplishment.
Steve
Pres.
Some constructive criticism for your design...no disrept whatsoever. Below are some considerations you may have overlooked.
1) From an engineering stanpoint, using two "truss's" running parallel with perpindicular connecting points is an inferior design to a triangulated construction. A trianglulated design will prove to be stronger and distribute the load better.
2) Higher HP setups will bend the floor panels with the front connection points your using. A more appropriate design is to tie the connection points into your subs for example.
3) The front brace you may end up bending that also...not certain of your wall thickness as well as the grade steel used.
Though i'm pointing out some of the negative aspects, overall, a good job and you should be proud of your accomplishment.
Steve
Pres.
Last edited by steve10; 06-16-2004 at 09:11 PM.
06-16-2004, 09:45 PM
#10
Launching!
Thread Starter
Thanks for the compliments guys. This will probably get pretty long, but I’ll try to explain a lot of the details about how I built it and the decisions I made along the way.
The first thing I built was the rear mount. I got the hole locations and plate spacing off of an extra LT1 rear end that we have. Knowing that it would end up way overbuilt, I would have liked to engineer it some, but was limited by the thickness of steel we had at work. The vertical plates are made of 3/8x2 cold rolled mild steel (same material as everything other than the tube) and the horizontal are from 1/4x4. Me and my brother machined each of these parts using the machine shop at his school so that they would fit together good. The extra hole in the vertical plate is for welding, so I could bolt the rod ends in there to hold them at the right spacing while welding on the top and bottom plates.
The next part I designed is the actual arm. The material I used was 1.25” OD x 0.095 electric resistance welded hot rolled 1026 steel. This is the cheap stuff (I got 23’ for $20), usually used for light structural construction like clothes lines. You may be wondering why I didn’t use heavier wall or higher grade (chrome-moly) steel. After some initial hand calculations trying to determine what tube to use out of what I had available, I found that this tube would be strong enough to handle more than I could ever throw at it. To verify my design, I ran a Finite Element Analysis on it, and the stress results are shown in the attachment. The analysis was run with the equivalent of 750 ft-lbs acting on the torque arm. The results show that the maximum stress (even at the stress concentrations) was around 20 ksi, with the vast majority well under 10 ksi. The material’s yield stress is 47 ksi, so using thicker wall tube or higher grade steel isn’t necessary.
Another interesting point is that people think that using chrome moly tubing makes components lighter in weight. Because the density of steel is the same regardless of composition, the only way to make parts lighter is to use thinner wall tubing. Since chrome moly steel has a higher yield strength, it allows added safety when going to a thinner wall. However, considering the stresses actually generated in applications such as this makes the use of more expensive chrome moly tubing less justified. Comparing 1.25” OD, 0.120” wall to 1.25” OD, 0.095” wall in the quantities used in a torque arm means that you save less than 1.5 pounds.
The construction of the arm was pretty straight forward, it just required a lot of time getting those angled and radius cuts right because all I had was a dremel. The threaded tube end inserts are made of 1.125” hex bar stock. Each insert is 1.5” long and turned down with a lathe to get it to slide into the tube around 1”. The threads are 3/4-16 tapped through the length of the inserts, and the rod ends used are QA1. The rears are just solid rod ends and the front is a spherical bearing rod end. The double adjuster on the bottom is also from QA1.
Now onto the final part, the front mount. This part is made from two 5/16x1 bars spaced apart 1” and welded to the mounting pads. I chose to orient the bars this way because putting them in this position gives the greatest stiffness in the vertical direction, which is the only force transferred into the front mount. When subjected to the equivalent of 750 ft-lbs at the rear wheels, the calculations show that the maximum stress was under 6 ksi and the maximum deflection was 0.006”, so bending it is of little concern. The bushing I used is a Prothane universal fit bushing (19-603, and I’ve got three extra if anyone wants one doesn’t want to spend a ton to get more than they need like I had to).
The total price for all my materials (tube, rod ends, and bushings) was $110. As far as the performance is concerned, the wheel hop is totally eliminated. I’ve had it installed for around 2000 miles and around 20 track launches with no problems yet. Everything looks as if it was just installed. You will see from my sig that my launches aren’t anything spectacular, but when they do get better, the torque arm will be the last thing on my mind.
If you made it this far, thanks for reading. I tried to explain most of the details my design, but if anybody wants to know more, feel free to ask.
Thanks,
Chris
The first thing I built was the rear mount. I got the hole locations and plate spacing off of an extra LT1 rear end that we have. Knowing that it would end up way overbuilt, I would have liked to engineer it some, but was limited by the thickness of steel we had at work. The vertical plates are made of 3/8x2 cold rolled mild steel (same material as everything other than the tube) and the horizontal are from 1/4x4. Me and my brother machined each of these parts using the machine shop at his school so that they would fit together good. The extra hole in the vertical plate is for welding, so I could bolt the rod ends in there to hold them at the right spacing while welding on the top and bottom plates.
The next part I designed is the actual arm. The material I used was 1.25” OD x 0.095 electric resistance welded hot rolled 1026 steel. This is the cheap stuff (I got 23’ for $20), usually used for light structural construction like clothes lines. You may be wondering why I didn’t use heavier wall or higher grade (chrome-moly) steel. After some initial hand calculations trying to determine what tube to use out of what I had available, I found that this tube would be strong enough to handle more than I could ever throw at it. To verify my design, I ran a Finite Element Analysis on it, and the stress results are shown in the attachment. The analysis was run with the equivalent of 750 ft-lbs acting on the torque arm. The results show that the maximum stress (even at the stress concentrations) was around 20 ksi, with the vast majority well under 10 ksi. The material’s yield stress is 47 ksi, so using thicker wall tube or higher grade steel isn’t necessary.
Another interesting point is that people think that using chrome moly tubing makes components lighter in weight. Because the density of steel is the same regardless of composition, the only way to make parts lighter is to use thinner wall tubing. Since chrome moly steel has a higher yield strength, it allows added safety when going to a thinner wall. However, considering the stresses actually generated in applications such as this makes the use of more expensive chrome moly tubing less justified. Comparing 1.25” OD, 0.120” wall to 1.25” OD, 0.095” wall in the quantities used in a torque arm means that you save less than 1.5 pounds.
The construction of the arm was pretty straight forward, it just required a lot of time getting those angled and radius cuts right because all I had was a dremel. The threaded tube end inserts are made of 1.125” hex bar stock. Each insert is 1.5” long and turned down with a lathe to get it to slide into the tube around 1”. The threads are 3/4-16 tapped through the length of the inserts, and the rod ends used are QA1. The rears are just solid rod ends and the front is a spherical bearing rod end. The double adjuster on the bottom is also from QA1.
Now onto the final part, the front mount. This part is made from two 5/16x1 bars spaced apart 1” and welded to the mounting pads. I chose to orient the bars this way because putting them in this position gives the greatest stiffness in the vertical direction, which is the only force transferred into the front mount. When subjected to the equivalent of 750 ft-lbs at the rear wheels, the calculations show that the maximum stress was under 6 ksi and the maximum deflection was 0.006”, so bending it is of little concern. The bushing I used is a Prothane universal fit bushing (19-603, and I’ve got three extra if anyone wants one doesn’t want to spend a ton to get more than they need like I had to).
The total price for all my materials (tube, rod ends, and bushings) was $110. As far as the performance is concerned, the wheel hop is totally eliminated. I’ve had it installed for around 2000 miles and around 20 track launches with no problems yet. Everything looks as if it was just installed. You will see from my sig that my launches aren’t anything spectacular, but when they do get better, the torque arm will be the last thing on my mind.
If you made it this far, thanks for reading. I tried to explain most of the details my design, but if anybody wants to know more, feel free to ask.
Thanks,
Chris
06-17-2004, 12:36 AM
#12
Looks like you did some homework. FEA is a great addition to analysing stress loads. If you've never worked with nastran, it's worth checking out as it is a fantastic program. http://www.nenastran.com/index.php
Though it may work well for your situation, I would keep track of your results in the areas I've discussed. It appears the FEA results may be a bit lacking from imput data...the moment stresses among others do not seem addressed. Deflection of less then .006 doesn't make sense, though i'm sure fits the data entered. Stresses i.e. shear stress, axial loading #'s are going to be hard to guess and use for imput #'s to FEA without actual testing an analysis from the area's of consideration. I'm unsure how you transferred you the limiting stresses placed on the arm i.e. 750ft/lbs...I'm unsure if you used that number as something that your engine would put out at a max tranferred to your driveline etc, I don't believe that number would be correct to use as your limiting #'s at the points of interest.
Regarding the materials used, chromoly's density is similar, though the carbon and chromium among other metals content is higher resulting in a harder material which will result in lower amt of deflection and deformation. This is one of the great benifits of using chromoly over other mild steels, ie 1020. The downside is since it deforms less, and is harder, it will be more brittle...as long as you stay above your fatique limit, it is very safe to use. and the choice of material from a strength to weight standpoint. Other areas of considering woudl be even the weld pool and surrounding area of mig over tig for example will result in a lower heat concentration area resulting in elongation of atoms creating higher deformation near the weld...small though present. Tig welding is a much better process regarding heat concentration so not to temper the surrounding areas differently.
This is all probably very boring to some...though material science, and M.E. design are facinating topics (to me at least). I really enjoy topics of discussion you brought up. Some folks don't have the knowlege or equiptment for testing and anaylsis, so real life testing is done instead. Though shooting from the hip with some designs can be inovative, it's great to see testing and analysis done from a higher level and a more detailed thought of how a product will theoretically perform before actual real life analysis.
Hopefully all your tests from a the theoretcal standpoint stands up to the real life tests. Pay attention to the areas that I've brought up. In the past, the some of the areas I've discussed have been a high stress point and have had plastic deformation as discussed. I wish you all the best!
Great stuff!
Steve
Pres.
Though it may work well for your situation, I would keep track of your results in the areas I've discussed. It appears the FEA results may be a bit lacking from imput data...the moment stresses among others do not seem addressed. Deflection of less then .006 doesn't make sense, though i'm sure fits the data entered. Stresses i.e. shear stress, axial loading #'s are going to be hard to guess and use for imput #'s to FEA without actual testing an analysis from the area's of consideration. I'm unsure how you transferred you the limiting stresses placed on the arm i.e. 750ft/lbs...I'm unsure if you used that number as something that your engine would put out at a max tranferred to your driveline etc, I don't believe that number would be correct to use as your limiting #'s at the points of interest.
Regarding the materials used, chromoly's density is similar, though the carbon and chromium among other metals content is higher resulting in a harder material which will result in lower amt of deflection and deformation. This is one of the great benifits of using chromoly over other mild steels, ie 1020. The downside is since it deforms less, and is harder, it will be more brittle...as long as you stay above your fatique limit, it is very safe to use. and the choice of material from a strength to weight standpoint. Other areas of considering woudl be even the weld pool and surrounding area of mig over tig for example will result in a lower heat concentration area resulting in elongation of atoms creating higher deformation near the weld...small though present. Tig welding is a much better process regarding heat concentration so not to temper the surrounding areas differently.
This is all probably very boring to some...though material science, and M.E. design are facinating topics (to me at least). I really enjoy topics of discussion you brought up. Some folks don't have the knowlege or equiptment for testing and anaylsis, so real life testing is done instead. Though shooting from the hip with some designs can be inovative, it's great to see testing and analysis done from a higher level and a more detailed thought of how a product will theoretically perform before actual real life analysis.
Hopefully all your tests from a the theoretcal standpoint stands up to the real life tests. Pay attention to the areas that I've brought up. In the past, the some of the areas I've discussed have been a high stress point and have had plastic deformation as discussed. I wish you all the best!
Great stuff!
Steve
Pres.
Last edited by steve10; 06-17-2004 at 03:30 PM.
06-17-2004, 08:31 AM
#13
As a mechanical engineer its all very interesting reading to me, and brings back memories of college (which was only 3 years ago!).
But anyways, impressive job on both fabbing, and engineering your own torque arm! You ought to sell them and make some money on the side
But anyways, impressive job on both fabbing, and engineering your own torque arm! You ought to sell them and make some money on the side
06-17-2004, 09:48 AM
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Chris, thanks for posting some of the details.
I may try making one for myself in the future. Regarding the threaded inserts you made for the tubing ends, Where would one find threaded hex bar stock to turn down for a slip fit inside the tubing and do you feel that method is strong enough vs threading the tubing ends directly?
Any links to material suppliers?
Is it necessary to use a urethane bushing on the front mount or is that more for noise control?
Steve
I may try making one for myself in the future. Regarding the threaded inserts you made for the tubing ends, Where would one find threaded hex bar stock to turn down for a slip fit inside the tubing and do you feel that method is strong enough vs threading the tubing ends directly?
Any links to material suppliers?
Is it necessary to use a urethane bushing on the front mount or is that more for noise control?
Steve
06-17-2004, 10:25 AM
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John, That looks similar to the Jegs style T-arm. How well does it work for you?
And another question for Chris, I see you used 750ftlbs of TQ in your equations.
I'm not sure why you used that number and I am certainly not an Engineer.
But for instance a engine making 500lbs/ft at the crank with a 3.06 1st gear and 3.50 rear gears, is sending 4800+lbs of TQ to the rear wheels and even more for a brief instant from torque converter fluid multiplication.
How does that fit into your equations?
Steve
And another question for Chris, I see you used 750ftlbs of TQ in your equations.
I'm not sure why you used that number and I am certainly not an Engineer.
But for instance a engine making 500lbs/ft at the crank with a 3.06 1st gear and 3.50 rear gears, is sending 4800+lbs of TQ to the rear wheels and even more for a brief instant from torque converter fluid multiplication.
How does that fit into your equations?
Steve
06-17-2004, 10:45 AM
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Very nice work.
Have you felt much of a difference off the line when compared to the stock arm? I also assume your rear mounting point for the LCA's is stock?
Have you felt much of a difference off the line when compared to the stock arm? I also assume your rear mounting point for the LCA's is stock?
06-17-2004, 12:26 PM
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Chris,
Great work!!
That looks very very similar to my Spohn TA down to the flat tunnel brace with out a dip in it. I am having a hell of a time finding a y-pipe to work with it. Can you give me any details on your y-pipe such as size or send me some pics. It would be greatly appreciated.
Thanks
Justin
Great work!!
That looks very very similar to my Spohn TA down to the flat tunnel brace with out a dip in it. I am having a hell of a time finding a y-pipe to work with it. Can you give me any details on your y-pipe such as size or send me some pics. It would be greatly appreciated.
Thanks
Justin
06-17-2004, 02:54 PM
#19
Originally Posted by S_J_H
John, That looks similar to the Jegs style T-arm. How well does it work for you?
And another question for Chris, I see you used 750ftlbs of TQ in your equations.
I'm not sure why you used that number and I am certainly not an Engineer.
But for instance a engine making 500lbs/ft at the crank with a 3.06 1st gear and 3.50 rear gears, is sending 4800+lbs of TQ to the rear wheels and even more for a brief instant from torque converter fluid multiplication.
How does that fit into your equations?
Steve
And another question for Chris, I see you used 750ftlbs of TQ in your equations.
I'm not sure why you used that number and I am certainly not an Engineer.
But for instance a engine making 500lbs/ft at the crank with a 3.06 1st gear and 3.50 rear gears, is sending 4800+lbs of TQ to the rear wheels and even more for a brief instant from torque converter fluid multiplication.
How does that fit into your equations?
Steve
06-17-2004, 04:08 PM
#20
Launching!
Thread Starter
S_J_H, you had a couple of questions...
First, the threaded tube inserts. Those were made from solid 1.125" hex bar stock, so I had to tap them in the lathe. During my research, I ran across a company that specializes in custom racing frames and suspension, Applied Racing Technology (www.appliedracing.com). They have a lot of cool stuff, and they offer the inserts completely machined. They call them "tube end adapters". Another note is that I bought all the QA1 parts directly from QA1. I didn't think they would let an individual buy from them, but they never asked if I was a business, so I didn't tell them that I wasn't. Even though plenty of other places sell those or similar rod ends, the one key part I couldn't find anywhere else was the double adjuster. Their prices were also lower than I found for the same parts elsewhere.
Your next question was about the 750 ft-lbs number. The reason why I chose this was because I knew the arm would be excessively strong and I wanted to demonstrate that by running the simulations with an unattainable level of torque. Well, unattainable for me, anyway! You mentioned the torque multiplication of the transmission, etc. I didn't think of it from that perspective. The way I thought of it was that if the rear wheels were delivering a certain amount of torque to the pavement, then by Newton's second law (second, right?), it has to be resisted by something. With the F-body suspension, the torque arm is what resists the vast majority of the axle rotation (maybe a small amount taken by LCA bushings and universal joint, but I neglected those). Resolving that torque to a tip force acting at the end of the spherical bearing rod end is the final step.
Chris
First, the threaded tube inserts. Those were made from solid 1.125" hex bar stock, so I had to tap them in the lathe. During my research, I ran across a company that specializes in custom racing frames and suspension, Applied Racing Technology (www.appliedracing.com). They have a lot of cool stuff, and they offer the inserts completely machined. They call them "tube end adapters". Another note is that I bought all the QA1 parts directly from QA1. I didn't think they would let an individual buy from them, but they never asked if I was a business, so I didn't tell them that I wasn't. Even though plenty of other places sell those or similar rod ends, the one key part I couldn't find anywhere else was the double adjuster. Their prices were also lower than I found for the same parts elsewhere.
Your next question was about the 750 ft-lbs number. The reason why I chose this was because I knew the arm would be excessively strong and I wanted to demonstrate that by running the simulations with an unattainable level of torque. Well, unattainable for me, anyway! You mentioned the torque multiplication of the transmission, etc. I didn't think of it from that perspective. The way I thought of it was that if the rear wheels were delivering a certain amount of torque to the pavement, then by Newton's second law (second, right?), it has to be resisted by something. With the F-body suspension, the torque arm is what resists the vast majority of the axle rotation (maybe a small amount taken by LCA bushings and universal joint, but I neglected those). Resolving that torque to a tip force acting at the end of the spherical bearing rod end is the final step.
Chris