I have a question concerning the rear spring on a Model A, vs the rear springs on a normal/newer rear leaf spring car. On the regular leaf spring car, if you take the weight off the rear axle, you can disconnect the rear springs from the body/shackles, and remove the axle and springs without issue. Why is it so dangerous to do that with the Model A. If you take the weight off the rear axle, why can't you disconnect the spring from the body, and remove the axle with the spring attached. I have read articles on the subject, but still confused. Thanks..TommyJ..
31 Model A rear spring
- Thread starter tommyleea
- Start date
Tommy - you can do this, but it's unadvisable. The Model A spring is under tremendous pressure when attached to the shackles. It is not slack (or nearly so) when at rest like many modern cars, that's why you have to use a spring spreader to install it. What holds the leaves together is a single bolt through the center of the leaves. The leaves at rest have curvatures much tighter than when assembled, and when you compress the leaves the energy to flatten them is stored in the leaf. If this (maybe 90+ year old) bolt breaks, then all that stored energy in the spring is released catastrophically. That is why you constrain the leaves with C-clamps and chain when you disassemble the spring on the bench. I've had that center bolt break on me when releasing it during disassembly of a spring, and it's frightening when you hear the BANG and everything jumps.
When in the car, not only is this spring contained within the channeled crossmember, the spring leaves are constrained by the two U-bolts that hold the spring assembly within the cross member.
So - it's not that you cannot remove the axle assembly with spring attached, rather it's a safety issue that you should not lest that single bolt fail. Body parts are slim protection against that much energy released at once. Use the spring spreader, spread the eyes to release tension on the shackles, remove the shackles and then drop the axle assembly with the spring extended on the spreader. If you need to work on the spring then release the tension using the spreader, and only then remove the spring from the frame.
We really don't want to read about you here as a "what not to do"...
ThirstyThirty
Senior Member
to do the job safely, calls for a Model A spring expander. even then... it is a task best accomplished with a full understanding of what you are doing, what can go wrong, the consequences of such... and a lot of well thought out attention to detail!!
uh-huh ~
uh-huh ~
Copy..Got it. Thanks
Copy..so the pressure isn't off the spring with the weight off the axle. That make sense. Thanks.
Tom Endy
Well-known member
Thanks Tom..That is great..
Tom, as always, says it best.
Bob Bidonde
Well-known member
The front & rear springs are stretched when installed. So regardless of the weight acting on those springs, you should use a spring spreader to safely remove them.
Phil Brown
Well-known member
The A also only has one spring streched out to support the cars weight where as a newer car has two springs with only one end in a shackle so there not streched or compressed to install (only after the cars weight is put on them)
Brentwood Bob
Well-known member
A good time to restore the spring. That old center bolt is an unknown.
I painted my springs (the rubbing surfaces) with graphite paint when I rebuilt the springs. Haven't finished the car enough to know if it makes a difference, but the leaves sure did slide together nicely when I assembled the springs. Some of the leaves were rust-pitted but I tried to smooth those out with a flap wheel without reducing the thickness.
nkaminar
Well-known member
The reason why the Model A springs are under tension is, as Phil Brown said, the springs on a modern car are attached to the frame at one end. That anchors the spring and keeps the axle in place. The springs on a Model A are not anchored but have shackles at both ends. So the tension keeps the axle more or less in the center of the car. A track bar will anchor the rear end to eliminate any side movement, however slight, in the rear end.
Diastole
Senior Member
Please advise: Rear spring bolt fractured!
My 30 coupe is getting an overdrive. I am in the planning stage.
The rear spring bolt is missing the bottom half. I can feel the fractured upper half in the hole and feel the nut end on top of the channeled cross member
What should I do in dropping the rear axle. As I let the axle down all but the last leaf should loosen and fall out and since nothing is retaining the spring it should be ok, correct?
Diastole in the Smokies
My 30 coupe is getting an overdrive. I am in the planning stage.
The rear spring bolt is missing the bottom half. I can feel the fractured upper half in the hole and feel the nut end on top of the channeled cross member
What should I do in dropping the rear axle. As I let the axle down all but the last leaf should loosen and fall out and since nothing is retaining the spring it should be ok, correct?
Diastole in the Smokies
1930artdeco
Well-known member
Two things:
I had to rebuild my Mitchell due to my mistake. I took the whole thing out at once but could not get it back in. I had to take the rear spring off, install it separately and then axle. But while it was out of the car I had at least one 6" clamp on it. going back in I had two more added and a chain-probably should have done that in the beginning. Either way I had to put it in separately and then the axle. Still hate dealing with that thing.
Diastole: with a broken bolt that means there is nothing holding that spring pack together. So I think you have one option: Release the tension very slowly by raising the body off of the axle or dropping the axle. Making sure that the spring can't fly off in any direction. Do this by clamping the spring pack together, lower, add a clamp/chain, lower and add a clamp etc., etc. I am sure someone smarter than me will chime in with a better idea. My 2 cents worth.
Mike
I had to rebuild my Mitchell due to my mistake. I took the whole thing out at once but could not get it back in. I had to take the rear spring off, install it separately and then axle. But while it was out of the car I had at least one 6" clamp on it. going back in I had two more added and a chain-probably should have done that in the beginning. Either way I had to put it in separately and then the axle. Still hate dealing with that thing.
Diastole: with a broken bolt that means there is nothing holding that spring pack together. So I think you have one option: Release the tension very slowly by raising the body off of the axle or dropping the axle. Making sure that the spring can't fly off in any direction. Do this by clamping the spring pack together, lower, add a clamp/chain, lower and add a clamp etc., etc. I am sure someone smarter than me will chime in with a better idea. My 2 cents worth.
Mike
katy
Well-known member
You'll still need a "spring spreader" for the main leaf and and when re-assembling.
I’d try to push the broken bolt upwards from the bottom, then install either a new one or a length of 3/8” all thread from the top to contain it. Do this with the two brackets still on. Then use the spreader, remove the spring shackles, drop the axle out of the way, remove the spreader, remove the brackets and remove the spring. You may have to gradually lengthen the all thread as the leaves separate.
BTW, if you’ve never used a spring spreader, you will be surprised at how much oomph it takes to expand it to push the spring. That’s how much energy you are containing from escaping.
The nut should be on the bottom of the spring, and it gets the threads of the bolt peened over after trimming to length. The square bolt head fits into the square hole in the crossmember to center the spring.
Charlie Stephens
Well-known member
You need the spreader. Check to see if your local club has one they loan.
Charlie Stephens
Charlie Stephens