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TR2/3/3A TR3A Chassis restoration

vype

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Hello everybody,

I am currently working on the restoration of the chassis of my TR3A.

I have a problem with the left lower fulcrum pin of the front suspension. The pin is twisted on its rear part and its fastening tabs are partially cracked.
I plan to cut the two existing brackets at their base and make new ones. Then remove the part of the bracket around the pin extremity and try to heat the pin to straighten it.Then solder the new long bracket at the pin extremity and finish by welding the two brackets on the frame.

Do you think it's a good idea and it's the right way ?
 

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TomMull

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CJD

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Like Tom says, that pin is the single hardest part to replace on a TR3. I would try to bend it back as you plan first, as it would save several weeks labor if the pin has to be replaced. On straightening:

I would not worry about heating, so long as you do not quick cool the pin at any time. Quick hardening can cause cracks, and with cracks it will eventually fail. The pin in factory form is almost dead soft.

The sleeve assembly that must go over the pin to hold the A-arm is a very precise fit. While straightening I would have both your A-arm and a new bushing kit on hand to conduct many "test fittings", making sure the pin is finally absolutely straight and un-mangled.

When done, the center of the outside of the a-arm MUST be dead center under the upper ball joint, within at least 1/16". If it is not, the suspension will bind at the trunnion, eventually causing failure.

You will also have to ensure the pins are located in the in/out direction properly, or the un-adjustable camber will be more positive than it already is stock.

In my opinion you do have to attempt the repair to your pins. Just be aware of the complication of the fix so it comes out good in the end.
 
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vype

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Thanks Tom and John for your feedback,

The link is very interesting and informative.
I hope I can straighten the fulcrum pin without having to disassemble everything like Kerry but if necessary ...

I intend to slide a tube of about 10 inches on the bearing surface of the ring, torch the axis near the weld with the turret and twist the axis gently using the tube as a lever arm (without hammering).
The most difficult will be to align the axis. It is a good idea to test directly with the arms of the wishbone.

But sorry John, I'm not sure I understood your explanation of how to check the alignment. Do I have to put the upper wishbone, the upper ball join, the vertical link and the trunnion up on the lower wishbone?
How can I check if the dead center under the upper ball joint is at least 1/16" ?
What do you mean about the in/out direction ?

Claude

 

Frank Canale

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Hi Claude, As John has stated this is a very complicated repair. Before You start to do any straitening it is important to establish a center line from front to back. I used a laser but a string will work. There is a frame drawing with detailed dimensions in the service manual. Everything is based on the centerline. The lower fulcrum pins are braced inside the spring tower so you must be very careful that you don't fix the lower fulcrum pin problem only to cause another problem with the upper fulcrum pin alignment. The frame is only 16 gauge sheetmetal channels welded together to form the frame tube. Becareful clamping to the frame as not to deform it. The outer most bracket that the end plate bolts to looks like it does not need to be removed. Place a heavy plate under the frame across both vertical walls of the frame and with a C clamp compress it back into position and re weld it. The fulcrum pin is cold roll steel and should not require any heat to bend it. Once you get it close you might be able to heat one side or the other and let the heat pull the pin one way or the other as it cools. I have done this repair and you do not want to remove the lower pin or its supporting brackets if you can avoid it. You can search[h=3]1960 TR3A starting chassis work to see detailed description of the process. GOOD LUCK and take your time.[/h]
 

bobhustead

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Once you have the bracket with the 2 bolt holes welded back in place, offering the end plate intermittently as you bend should provide a handy indicator whether you have the bend right. As noted, removal of the fulcrum pin will likely produce practically irreparable harm.
Bob
 

CJD

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I intentionally didn't provide a means of measuring the alignment of the upper and lower control arms...as it is going to take some real ingenuity to do it! I merely point out that they absolutely must be aligned to prevent binding. On most cars you have an upper AND lower ball joint, so the ball joints can absorb any mis-alignment, and the worst case you change caster over the suspension travel. The TR has a lower trunnion, which only pivots in one direction, not all 360 degrees like a ball joint. So a mis-alignment in the TR will put a bind on the brass trunnion, eventually leading to a broken trunnion or vertical link.

Assembling the entire suspension will definitely work to test alignment...but should not be necessary as you are doing the straightening. You will have to assemble the upper ball joint to measure the relative position of the lower a-arm center point. with strings/levels and some ingenuity it should not be too hard.
 
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vype

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John and Bob,
Thank you for these information.
As Frank advised I will take my time and try to find a way to check the alignment before doing anything on the chassis.
I already have some ideas. I'll submit them to you when it's more concrete.
 
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