Tensile Strength

[wil_wil2]

Does anybody know what would be the easiest way to test tensile strength of bolts.

[Pineapple]

You need load cell to measure tensile force. Also need means to secure bolt on both ends. No welding the bolt cause the heat will change its property. Need digital load display which has max max hold display. You'll need enough bolts to test and use avarage for result.
Why do you need to test them?

[wil_wil2]

I have access to a test bed(tests linear breaking strengths) at work, but it will only test root strength, not tensile. I need to find bolts strong enough to support the load from my torgue converter on my '68. I have already went through a set of grade 5, 8, 10 bolts. They all broke when under heavy load.

So I was either thinking of finding some grade 16-18 bolts or getting some machine at work(this is why I need to test tensile strength).

[Pineapple]

You testing tensile or shear? Show me photo of the broken bolt. Either use bigger bolt, more bolts or custom make them with stronger material (4140, A2, D2, 17-4PH) and heat treat (full, case harden) them to spec.
You better find a way to calculate the load on the bolt first then look for bolt/material.

[wil_wil2]

I can test root shear, but I want to test root tensile if I have bolts machined.
I can't use bigger, or more bolts, because these are the bolts that connect my flexplate to my torque converter.
If I machine the bolts I will be making it out of 4140 steel, or a type of cold rolled, or a titanium. But if I machine them I want to be able to test tensile strength.
I don't know how I would be able to test the load that is put on them. The reason they break is because they are twisting from engine torque.

[Pineapple]

You need to test shear stength, not tensile stength. You need hard bolt. Maybe bolt with short shoulder to reduce stress. Drill the thread on torque converter side so the shoulder go in. This way the shoulder take the load and not the threads.

[Pineapple]

You can remove the threaded blocks on the convertor and weld on bigger threaded ones. Or even weld on more.
Make sure the bolts you use are not too long and the flexplate is tight on the convertor. If the flexplate is lose, the shock from start will cut the bolts off.

BTW do not over torque the bolt.

[wil_wil2]

I will be testing shear strength, but I want to be able to test tensile as well. I am already using bolts with minimal shoulder. It is not possible for me to put the shoulder in the torque converter, the bolt comes through the flexplate and then into the torque converter.

You can't weld onto the torque converter, because of the metal it is already made from(I had already thought about this and tried).
The torque converter and flexplate are not tight against one another(I already knew this was the problem). So when I initially installed the tranny I called around and asked to find out the best way to correct the problem, and I was told just to use spacers and it should be fine.

So I need to find a high grade bolt that is easily strong enough(probably going to machine them). And if I machine them I want to test the tensile strength to make sure everything is strong.

[Pineapple]

Weld the spacer on the flexplate. Make sure its tight on the bolt. If the flexplate is lose, nothing will hold. Either the bolt break or flexplate. My stock torque convertor got welding all over it. Unless you got one that is casted there is nothing wrong with welding.
Look up grade 8 bolt spec and spec material and heat threat with higher stress value.

[wil_wil2]

I have tried to weld on my torque converter when I first installed it, but it will not ground through the converter. I have already went through grade 5, 8, 10 bolts none of them were able to withstand the twist of the motor. Normally the grade 8 and 10 bolts should work, but with this space I'm dealing with allows the motor to twist more.

[Pineapple]

It doesn't work because you're not shearing them. You're bending them till they break which reduce the load carrying of the bolt.

Weld spacer on flex plate or thicken the plate. Lose spacer between the plate and convertor won't work. You'll need to balance the flexplate after you weld the spacers.

Unless the convertor is plastic, there is no reason why metal can't ground. It may have coating/paint that prevent current.

[wil_wil2]

Yes I know why they are breaking.

I dont want to weld onto my flexplate. I don't think welding the spacers in place will make any difference, as they are tight when installed.

I have never seen a torque converter that can be welded. You have to remember not all types of metal can be used in welding. It is the same way with my carb, it cannot be welded.

Anyways, I talked to my dad(who is my foreman), and our test bed can be set-up to test tensile strength after all. But thanks for all your input Pineapple.

[Pineapple]

You've never seen one but I happen to have photo on hand:

All the tabs are welded and the whole thing is sheetmetal. I can see weld burn on the other side for all the fins inside the converter.

Welding the spacer will help. With spacer moving between the flexplate and converter, you got 2 shear planes. This create a bending moment on the bolt instead of pure shear.
Oh well what does a fucking engineer knows anyway.

BTW I'll rather the bolts break than the engine trying to twist the flexplate off the converter.

[wil_wil2]

Well, I have never seen that before, all the ones I have used/worked on were all cast, so nohing was welded on. I have only tried to weld on it the once, and I could get current to run through it.
I just figured if the spacer was tight there would be no movement within it.

So do you think if I just tacked(instead of a full weld) the spacers on the flexpate, it would take out the twist that is put on the bolts?

[Pineapple]

That's 90 Celica auto torque converter.

It may take a bit more then a tack to hold the spacer. Also make sure the hole is just enough for the bolt to go through. Put as much tack as you can all around the spacer.
You can't weld cast but you can blaze it.

[wil_wil2]

I dont know how much more I can do besides a tack unless I pull the tranny back so I can get proper access to the flexplate.
By blaze do you mean braze? as in metal fusion?

[wil_wil2]

I am surprised no one else has had any imput on this subject. But your advice is greatly appreciated, none the less.