Swing Arm Pinch Bolt

[Tedredamphi]

:032:What is the story on the swing arm pinch bolt (4-20-11) that Hugh Gordon is referring to in his latest weekend special? "Never touch it! Never remove it!" is what he says, but why? Couldn't come up with an explanation by searching the archives.
Thanks,
Ted

 

[Ken Chambers]

NEVER drive the pinch bolt out or in!

Two larger heavy duty spring washers on the inner end of the solid
axle pull with a substantial amount of force against the pinch bolt.
The pinch bolt is all that holds the trailing arm and accompanying
brake and wheel components from coming off the solid axle. The bolt
lines up as an interference fit in a circular groove near the axle
end. Same setup on both front and rear suspension.

To remove a trailing arm it is necessary to either: 1) remove the
entire solid axle axle assembly and relieve the spring tension using
the large adjusting nuts, or 2) remove the grease fitting on the end
of the solid axle and use a rather special puller to pull on the axle
against the trailing arm to overcome the spring pressure so the pinch
bolt can then be slid out. Need to use the same puller technique to
reinstall the pinch bolt.

Just so happen to be performing this maintenance right now rebuilding
the front end with new brass bushings and tie rod ends.

Ken Chambers, CA
'64 Red



On Apr 25, 2008, at 9:35 PM, Tedredamphi wrote:

> What is the story on the swing arm pinch bolt (4-20-11) that Hugh
> Gordon is referring to in his latest weekend special? "Never touch
> it! Never remove it!" is what he says, but why? Couldn't come up
> with an explanation by searching the archives.
> Thanks,
> Ted
>

 

[Ron Green]

The special tool works great as I just updated my pinch bolts a month ago. Gord has access to this tool (for sale). I went from grade 10 to 12.9 grade which will not stretch and will tighten things up. You must also use grade 10 washers and nuts if unable to find 12.9. A world of difference when driving.

 

[jwillia]

Ron

Which hardware did you upgrade and where did you get it ? I am just getting ready to put this back together.

Thanks Jeff


To: jeffreyd_7@hotmail.comSubject: RE: [General Amphicar Discussion-t-19965] Re: Swing Arm Pinch BoltDate: Sun, 27 Apr 2008 06:35:28 -0400From:



The special tool works great as I just updated my pinch bolts a month ago. Gord has access to this tool (for sale). I went from grade 10 to 12.9 grade which will not stretch and will tighten things up. You must also use grade 10 washers and nuts if unable to find 12.9. A world of difference when driving.

 

[Tedredamphi]

Ron,
I'd also be interested to know where you purchased grade 12.9 pinch bolts and hardware?
Thanks,
Ted

 

[PeterP]

Anyone have a picture of this thing?

 

[HDavidS]

Here's a photo of a 1/43 scale miniature (4 1/2") that comes mounted on a plinth in a display case. $69 plus 7.95 shpg - Also in Blue, Mint or White.


----- Original Message -----
From: PeterP
To: dave@miniauto.com
Sent: Sunday, April 27, 2008 6:44 PM
Subject: RE: [General Amphicar Discussion-t-19965] Re: Swing Arm Pinch Bolt


Anyone have a picture of this thing?





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[Ron Green]

I went to a local speciality commercial hardware supplier that caters to construction contractors. Fastenal ( http://www.fastenal.com/ ) is where I bought them however any decent supplier should be able to help you out.

The bolts are allen cap screw (hex heads need ordered from overseas). Are 10MM x 80 MM long with a 1.25 fine thread. I use 2 washers on top and 2 on bottom and crank them down. Let sit overnight and check tightness again. Any play will be gone.

 

[PeterP]

BoltDepot seems to have a pretty good assortment of grade 12.9 hardware. I have not ordered anything from them before, but they are well regarded online:

Metric socket products, Metric socket head screws, Steel grade 12.9

I'll order from them when it's time to put my rear axles back together and let everyone know how it goes.

 

[mike_israel]

From years back I know there is a reason why gorilla tightening the pinch bolt is not considered a safe or permanent fix.* I do not recall why but am sure someone can chime in.
Mike

 

[Ron Green]

From the way back achieve machine Billy Syx recommended this (grade 8) to get a few extra miles out of your expensive axle.

I think that not having these extremely tight will do more harm to both the axle and your wallet after you have ovaled things. I could tell the handling difference immediately after I cinched them up as my one was a tad loose.

 

[Canadian four amphs]

Late getting on the topic here,.
but as Ron Said I do have the special tool needed to change these bolts.
Jeff has a bunch made up also the one for the rear axle to pull it threw the Bearing.I sell them for Him..$50 a tool.
I do not know why Hugh made that remark about not taking this bolt out. with the tool I take them off on EVERY car I restore or repair.
Now I have found that on some car the front and the rear have diffent tread sizes in the greese zerk so need to know what your cars have.
These tools pull the tentinon on the swing arm and bolt just drops in, Tighten and your done!
GORD

 

[Ken Chambers]

Super tightening is a band aid for a problem. My car had very bad
ovaled holes in the trailing arms at the solid axle attach point along
with atrocious handling characteristics. On the road the car would
fish-tail about. Leading into a curve it would be necessary to
compensate for the fishtail with an opposite steering correction.
Very squirrelly.

So last year I rebuilt the entire rear suspension on my car. The
ovaled holes were bored round and steel bushings machined and
installed where there were none. Like night and day. It now drives
like a car - not a boat - on the road. No more fishtailing.

As Ron can attest, the handling of his car improved by clamping down
tightly on the pinch bolts so it's evident his trailing arm are
ovaled. But I would say that's a short term solution at best and a
dangerous one at worst. The trailing arms are cast iron - not a very
ductile material. There's a possibility the split clamp in the
trailing arm could break if over stressed.

Personally I think that joint is a weak design point in the Amphicar.
Both the front and rear are the same design but most of the driving
forces are concentrated laterally on rear joint that is only about an
inch in length. Any looseness works the metal resulting in an ovaled
hole over time. The solid axle itself is hardened so all the wear
occurs in the trailing arm.

It's easy to check that joint for looseness. With the car jacked up,
grab the tire at the rear and push and pull. If the pinch bolt joint
is loose you'll feel it and hear a clunk cluck. You may see a bit of
movement from the wheel bearings so try to discern any difference by
forcing the tire itself at opposite sides, left/right and top/bottom.
I had about half an inch of movement at the rear of the tire. Now,
after the rebuild it's rock solid with no movement at all.

It would be informative to find out if other cars have a problem with
the pinch bolt joint and if it's mileage related. My car has around
36K miles.

Been meaning to finish up that article to the club newsletter about
the trailing arm rebuild...

Ken Chambers, CA
'64 Red



On Apr 28, 2008, at 10:03 AM, mike_israel wrote:

> From years back I know there is a reason why gorilla tightening the
> pinch bolt is not considered a safe or permanent fix.* I do not
> recall why but am sure someone can chime in.
> Mike
>

 

[DavidC]

Ken is right. Once the axle housing has begun to go oval the only answer is to machine them out and sleeve them. Replacing / overtightening the pinch bolt really only shows you how good the Amphicar handling can be. If there is any sideways movement then it needs fixing. The reason for not removing the rear bolt is that it is very difficult to get everything back together as well as the factory. The clamping area has to be super clean, the right tension has to be set with the dished washers and the bolt has to be the correct tightness.

What worries me about super high tensile bolts is that those sorts of bolts can be brittle so instead of stretching they just snap. I've seen a few cars where the rear wheel has come off, it causes a lot of damage to the tunnel area as the driveshaft is pulled out however normally it happens at low speed.

It is a bit of a weak point in design but remember the tyres Amphicar had originally. The tyres we use today cause much greater loads on the suspension which is also why the front wheel bearings can be an issue.

The problem is more related to miles and type of roads / driving style etc. I think if a car has done more than 20K miles it may well need some sort of attention. The annual safety test here means the cars never get so bad that you need opposite lock on corners !

Other areas of wear that can cause the same symptoms are the brass bushes and sometimes the axle itself is worn.

David C in the UK

 

[Ron Green]

The case harden 12.9 bolts are much better then the original grade 5 factory bolt which is easy to over tighten and stretch or in a extreme case break off. Even when applying a normal tork I would trust a 12.9 bolt more so then the inadequate factory one in my opinion.

I totally rebuild my swing arms and upgraded to the new axle design 4 years ago. I am lucky as I caught the play before any serious damage was done. I wish I had a better grade bolt when I did the rebuild.