pinch bolt confusion

Jon March

Member
1) Nowhere in the manuals, nor did folks mention, to be sure that when assembling the rear axle/tube/tension nuts/oscillating arm - to be sure to go to the car and remove the little L-shaped brake cable/hose bracket:
>> it needs to go ONTO the pinch bolt before you put it all together and set the correct "gravity-drag" for the oscillating arm.

So lets say you did all the setting up of the assembly , and put the correct tightness with the axle tube/flange and the oscillating arm....and say you DID forget to put the L-shaped brake line support under the pinch bolt.:
QUESTION: once the nut at the bottom is loosened, should the pinch bolt come right out, or is there (supposed? to be / sometimes there is??) some sort of side-tension on the pinch bolt being applied by the double-nuts & cupped spring washers?
Here is why I ask: with the frequent mention of a special tool that gets threaded into the M8 grease fitting hole at the end of the axle, I (apparently wrongly) thought that it was meant to relieve some sideways "pull" by the U-channel in the axle end, caused by the cupped washers and double nut tension setting. But after setting my oscillating arm tension exactly correctly so that it would stay at 3 oclock horizontal unless helped downward and installing the axle into the body tube and driveshaft carefully into the trans - thats whrn i discovered i had forgotten the brake line bracket goes under the head of the pinch bolt.
Now i was worried, because i didnt have the tool that i could have sworn was needed to help relieve the side tension, to be able to remove the pinch bolt without scoring it upon re-insertion. I quickly looked in the Maint Manual, and saw an AC15 U-shaped puller-bracket tool in a pic.] So i went to home depo to make up a DIY tool that would screw/nut washer into the greasefitting hole to help relieve any tension.
But before attaching my new contraption, i tried the nut and pinch bolt...and lo and behold: it came right out - there was NO side force to even RELIEVE.

Im frustrated and confused. First, the manual doesnt tell you to remember that goddamn bracket.
...Second: am i crazy? -I could have sworn i remembered Gord or someone saying you need some way to relieve tension on the side of the pinch bolt , or without the tool, the u-channell wouldnt line up, the bolt would be not only stiff to remove ...but the sharp edges of the axle u-channel will scounge the bolt going in, creating rough scars exactly where it wants to seat smoothly in the channel when tightened..

So, is the pinch bolt supposed to be able to just pull right the f. out after the back-nuts have been tensioned per instruction? (Actually tensioned even a little tighter - 1/2 turn instead of 1/3)

Then i went to the manual to read more carefully about the AC15/22/2 u-bracketand threaded bolt/nut/washer contraption, and although it mentions using it to help pull the axle INTO the oscillating arm (for folks that didnt go all they way and remove the axle to set the tension, etc) - but i cant find it mentioned to use that tool to relieve tensioning side pressure on the pinch bolt to prevent scoring it. Am i dreaming?? Please clarify!

i dont want to introduce "play" with a defective understanding of the forces that need to be correct - and that u-channell edge is awfully sharp and even cuts into grade 12.9 bolts easily.

(see other thread for that info)

Screen shot 2017-08-02 at 2.24.58 AM.png
Screen shot 2017-08-02 at 1.41.22 AM.png
 
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mschlem

Amphicar Expert & Former IAOC President
I'm sorry to tell you, but what you are thinking is correct....if all is set properly, you shouldn't be able to freely slide the pinch bolt out.
The torque on the bolt isn't critical from a "holding the oscillating arm tight" point of view. The bolt is acting more like a pin in the groove of the stub axle. The bolt drops in freely (with the inside tension released) and then it's drawn back with the big nut on the inner end of the stub axle.
Proper thing would be to go through the tensioning process again....but you are far from the first person who forgot that bracket. My guess is many of those folks did not re-set the tension. To be honest, many people don't set it correctly to begin with! That's the value of a group like this, to help people learn what is and isn't right.

Marc.
 

Jon March

Member
MS - you are a kind and empathetic counsellor!

Well - being nearly certain that I recalled that (once the proper arm-drag is locked in) that there should be SOME sideways tension on the pinch bolt, I did indeed remove the whole assembly (at least the drivers side--so far)

Its a heavy assembly, but 2 milkcrates are a perfect height platform after pulling them out.Oof course, now that the entire accordian-booted driveshaft and hub are mounted in the hub, i cant very well do the "tube in the vice/ oscillating arm gravity-drag"-procedure it a weighs too much
But 2 things are on my side to help me guesstimate how tight it all should be

1) the Maint manual says to tighten the 1st nut so that the Belle springwashers are barely rotatable my fingers..
...then turn 1/3rd past that - i actually did more like 1/2 tyrn to get the oscillating arm to lust stand horizontally at 3 oclock without falling...
Maybe my springwashers are tired? Does this happen / are they a routine replacement?

2)when all was tightened, the tube was quite hard to turn with both hands gripping it while oscillating arm was held still.


But here is where im not clear:

If you tighten the pinchbolt and oscillating arm onto the axle end before you set the springwasher tension, the oscillating arm will grab onto the axle end very strong - and wont allow the washers to apply proper sideways pull on the pinchbolt.

but if you leave the pinchbolt in its slot just finger-tight (so that the springwashers can pull the axle thru the arm until there is a bit of side-pull on the shaft of the pinchbolt..... I cant imagine continuing to turn the rear nut with to achieve correct assembly-tension between the tube and arm
- that is much more force, and would gouge the side of the bolt and possibly the u-channell in the end of the axle!

So how to you achieve the correct pulling-force on the side of the pinchbolt to keep it against the flange and prevent future "play".. (requiring the AC12 (or other DIY solution) tension-relieveing device, to remove side-tension on the pinchbolt when you want to remove /re-insert it??

,...but then continue to have the increased tension to hold the oscillating arm at the proper drag-setting (way too much to ask of just a tiny contact area on the side shaft of the pinch bolt.


It seems to need to be a 2-step process
1) setting just enough tension on the pinch bolt
2) tightening to far more tension (this time with the pinchbolt now tightened fully, with oscillating arm firmly grasping the end of the axle - to achieve proper drag-tension against the buffer washer between the oscillating arm and outer tube-flange brass bushing.
PS - which brings to mind: keep the exle end where it gies into the oscillating arm dry for best grab... -
ie: would light oil or grease screw up the needed "grip" on that small shaft-end.??
 

mschlem

Amphicar Expert & Former IAOC President
I do the "vice/drop test" that you mentioned with the driveshafts installed.
I put the pinch bolt in (with all tension on the stub staff removed) and finger tight the nut. Then I draw the inner nut on the stub shaft just enough to nicely seat the back of the oscillating arm against the face of the bushing/washer on the round housing. I then tighten the pinch bolt. I did not use a specific torque setting, just tightened using good judgement. Then I proceeded with tightening the nuts on the inner of the stub shaft. I tighten until the oscillating arm assembly just barely (or not at all) drops from the 3:00 position. (Remember, you will have the weight of the wheel installed later which will help even more with the rotational movement). In the end, the housing was quite hard to rotate by hand.
The only thing that I might change after reading some of the other recent posts is maybe I would double check and get a higher grade bolt (I used one from Gordon's - not sure what it is), and check the torque....again, not because I think it is overly critical, but mainly to verify that my best judgement wasn't too much or too little.
And to answer one of your other questions....the end of my stub axle was dry where the oscillating arm attached.

Have fun!
Marc.
 
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Jon March

Member
Boy , i would love comment from Gord, Dave, and/or the Chapmans here.... (dry vs greased . how to set correct side-tenion on bolt shaft before tightening the pinch bolt, etc
 

SNOWBIRD

Amphicar Expert
To much reading... All you need is Tool #12(read info above)Jeff in Toronto makes this tool.
I can get and sell for him.
Tighten tool, drop bolt in. put on nut Very tight, Your DONE! Take tool off.
Do it all the time..


IS part #21 in place the large washer?

20s.jpg
 
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Jon March

Member
Gord-my problem is not the pulling tool to relieve side tension on the bolt… my problem is that even after I thought I sent the correct drag tension with the large nuts on the back that there was no tension at all on the bolt: it slid right out even...without the AC 12 / tension relief tool .

That was my question as to what I did wrong if I tightened it up for the proper drag on the assembly and yet there was no side tension on the pinchbolt, and it pulls out freely?!
 
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strandweiss62

Active Member
Did you really separate axle and Swing arm during restauration?
Otherwise they can be rusted together, or someone welded them.

You should grease all parts before assembling and tightening the back nuts.
If you can pull of the swing arm now, you can assemble a spacer disc (like 5-21-55) on the outside, to set correct torque.
 

Jon March

Member
Oh, it was ALL apart!!

And i took both assemblies out- to re-do

While out, im gonna put speedi sleeves to eliminate the wear-lines from the seals
 
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Must use a 12.9 grade pinch bolt. They should really only be used once, also nut must be same 12.9 grade. The real problem here is they work loose and then the housing then wears oval - the forces are very high when cornering - and the housing is much softer than the shaft. To make an Amphicar stable at high speed this must be right. A lot of cars you can see or hear movement if you hold the rear wheel at 12 and 6 and pull/push. The best way is to machine and put a split sleeve (stainless) in the housing and this then clamps to the shaft with the pinch bolt.
 
Here you go, dad said the housing is machined and the stainless sleeve fitted, all to very tight tolerances. The split is so the high tensile pinch bolt can squeeze it on to shaft.
This was done almost 20 years and thousands of miles ago Still no sideways movement at all. It's on our main 80mph Amphicar.
acarpivot.JPG
 

Jon March

Member
Nice work! - a couple comments:

What would you recommend as a source for the hardware?
Fastenal, here in the states, is a popular place, but when i asked where they get their bolts of that type, they said "R.O.C." - and ive been warned that Chinese manufacture, at the all-important micron level, is nowhere near the quality of the steel from other, better QC countries (Germany, maybe Russia?) PS - i think i recall seeing that maximum safe torque on a matching12.9 bolt & nut combo is about 61 ft/lb?

That said - I got a warning-comment from a respected Amphi restorer here, whose friend is an aircraft engineer, warning that 12.9 might pose a danger under those stresses;

to wit: a grade 10 is a bit more "forgiving" under stress, whereas a 12.9 is far more brittle, and in the wrong circumstances have been known to just snap. Nothing youd want to risk at that assembly....

Made sense to me - your reflections on this perspective?
 
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Very difficult to get quality fasteners now. This was designed and put together by a "proper" engineering company in Birmingham who did prototype work for Landrover. Dad thinks they skimmed the face where it goes on the brass bush and then milled / drilled / reamed 90 degrees to that but see they didn't drill all the way though. Top quality work. It all works superbly and has never been apart. Well of course the driveshafts have been changed a few times but we never undo the pinch bolt ! The other think we do is rotate the housing by 1/6 every year or two such that there is no wear spot on the brass bush. That is what the red dot is about. Re fasteners, Dad looks for aircraft companies. He bought a lot of stuff in the 90s when the Concord production stopped and they sold of their stock, quite a bit of that holds our cars together.
 

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