Tube size/wall for trans mount

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Tube size/wall for trans mount

Post by BOOT » Wed Mar 21, 2018 11:44 pm

Gonna make a new trans x-member for a 2nd gen s10, it's a manual 2.2 so no big load but gonna drag it some. What size tube & wall should I use? I understand more od is stiffer than wall thickness.
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Re: Tube size/wall for trans mount

Post by BOOT » Sun Mar 25, 2018 12:56 am

Seriously, couldn't get an answer on YB either LOL Ah well I'll use 1-3/4 .120
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Re: Tube size/wall for trans mount

Post by mk e » Sun Mar 25, 2018 11:20 am

BOOT wrote:
Sun Mar 25, 2018 12:56 am
Seriously, couldn't get an answer on YB either LOL Ah well I'll use 1-3/4 .120
That seems way plenty....but i've never build one so I didn't what to comment. If you have room, going up to 2" would let you drop the wall to .060 and have almost exactly the same strength but just over 1/2 the weight...bending strength is dia^4 so a small increase goes a very long way.
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Re: Tube size/wall for trans mount

Post by pdq67 » Mon Mar 26, 2018 6:54 pm

We used to buy tubular tranny mount kits from W/JCW years ago, but I don't know if they still sell them or not?

The kits were in with their engine transplant parts.

Back then the tubular tranny kits were so cheap that I would have been hard pressed to make one..

At one time we could buy almost everything but headers from them to put any engine into any vehicle! The Jeep conversions were way helpful...

Totally off topic, but our beloved old SBC engines have three cast-iron exhaust manifolds that allow installation of it in about anything.

Early top 265 and later V-8 Monza top logs, ramshorns, and finally the bottom logs. And if you look, you will find truck and 'Vette stainless steel tubular header type exhaust manifolds too..

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Re: Tube size/wall for trans mount

Post by BOOT » Mon Mar 26, 2018 9:27 pm

idk bout 2" or larger, .060 is pretty much 16ga exhaust pipe(I'm sure the steel is better than exhaust pipe but just saying)

I've seen a few decent kits on ebay, summit, or speedway for example https://www.speedwaymotors.com/Speedway ... ,4219.html Most kits don't say the tube size or wall(that one does). I got time so I like to explore options and often something turns out a bit better if you make it yourself. I can get some straight pipe cheap n bend it at a friends as well, cheaper would be nice as I am limiting myself to a very tight budget. I've had a few sbc s10's and used manifolds for one because it was easy, this 2.2 is more of a personal challenge.

Also doing the exhaust myself so I'll just have to wait n see if I even need to bend any.
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Re: Tube size/wall for trans mount

Post by mk e » Tue Mar 27, 2018 2:23 pm

I built a whole race car using 0.028". I also build a car car like thing from exhaust tubing once. Just saying :)

Modern chassis are sheetmetal. They work because the whole surface is loaded making the load everywhere small. With tubing stuff you look at how much load, what will fit, and also will it see livsl impacts that cause dent or damage the tube. With thin wall tubing the weight is proportional to diameter but bending strength is proportional to dia^4, so strength hoes up WAY faster than weight as you increase dia....then you can tb in it out to the strength you need and have a much lighter design.

Just to hold up the trans behind a 2.2l.... I wouldnt think twice about using 2" exhaust tubing unless you need to put holes or notches in it, then the areas around the holes and notches will need more metal.
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Re: Tube size/wall for trans mount

Post by pdq67 » Wed Mar 28, 2018 10:41 pm

Who had the AA/FA with a, "muffler moly", frontend on it??

I think the story was that the front was always getting dinged so it was easier to fix tailpipe than real moly frame tubes...

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Re: Tube size/wall for trans mount

Post by Hrdlx62 » Thu Mar 29, 2018 2:36 pm

Google, transmission cross member kit. Your answer is within.

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Re: Tube size/wall for trans mount

Post by RCJ » Thu Mar 29, 2018 8:39 pm

I would 1 1/2 x.125 dom. I have tried the larger dia. and thinner pipe, It doesn't work as good as the smaller thicker pipe.If space was a problem I would use 1 1/4 x.125 dom and add some small braces or gussets.

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Re: Tube size/wall for trans mount

Post by mk e » Fri Mar 30, 2018 9:06 am

RCJ wrote:
Thu Mar 29, 2018 8:39 pm
I would 1 1/2 x.125 dom. I have tried the larger dia. and thinner pipe, It doesn't work as good as the smaller thicker pipe.If space was a problem I would use 1 1/4 x.125 dom and add some small braces or gussets.
Just curious, was there a problem with the larger, thinner tubing? or was it just a lot easier to work with heavier wall tubing? Or something else?
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Re: Tube size/wall for trans mount

Post by BOOT » Fri Mar 30, 2018 3:24 pm

RCJ wrote:
Thu Mar 29, 2018 8:39 pm
I would 1 1/2 x.125 dom. I have tried the larger dia. and thinner pipe, It doesn't work as good as the smaller thicker pipe.If space was a problem I would use 1 1/4 x.125 dom and add some small braces or gussets.
Some gussets or bracing is always a nice addition, I've herd of some bolt-in tube cross members sagging once the load was placed on them for certain cars.
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Re: Tube size/wall for trans mount

Post by mk e » Sat Mar 31, 2018 6:22 am

BOOT wrote:
Fri Mar 30, 2018 3:24 pm
Some gussets or bracing is always a nice addition, I've herd of some bolt-in tube cross members sagging once the load was placed on them for certain cars.
That is the reason for larger diameters or taller general profile, they are much more rigid for the same weight. But smaller thicker tubes are easier to fit and work with so that tends to be the preference if weight is not really a concern. Also bends are bad, notches in the top of bottom are bad, holes are usually not too bad unless they are removing more than 50% of the material or are not centered up/down. just general fabrication good practice rules.
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Re: Tube size/wall for trans mount

Post by 77cruiser » Sun Apr 01, 2018 1:03 pm

How long is it? Is it straight or bent?
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Re: Tube size/wall for trans mount

Post by BOOT » Sun Apr 01, 2018 6:45 pm

I've still not measured it really or checked how the exhaust will run. Bout 3 feet and might not need a bent or only one side for the single exhaust pipe. Kinda leaning towards larger tube size n dual bends incase I v8 or v6 it later, but if I can get away with straight for now I'll do that later.
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Re: Tube size/wall for trans mount

Post by RCJ » Mon Apr 02, 2018 6:15 am

With the larger dia. thinner tube once you start adding tabs ,welding, etc..It would fail at those points.I know the argument would be to redesign the mounts to spread the load or you are not welding correctly but those did not work as good as adding mass back in to the pipe.

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