Washer?

[bball7754]

I have been looking to identify and source these washers off and on for several years.  They are on my Mallock, and are used on either side of a large bushing inside of a boss on the chassis, to which an aluminum plate is bolted and used as part of the engine mount.

 

They seem to be made of some type of fibrous material, sort of fabric like.  They are finally disintegrating, and the reinforced rubber replacements didn’t last 3 race weekends.

 

I know there are some excellent Google researchers here, with more knowledge and experience than mine.  Engine is currently out, so now is the time to replace.  An aeronautical engineer came up with this design when he built a replacement chassis, in case that helps.

 

A photo in situ, and a blurry photo to give a sense of size.

 

 

Edited August 29, 2023 by bball7754

[MV8]

Do you have a picture of the components? I expect the stack of washers was added in order to use an extra long bolt to move the aircraft bolt unthreaded, thicker shank completely through the aluminum plate but usually car parts are so over engineered/over sized that low-grade hardware store fasteners are more than adequate.

It looks like there are four rubber washers when there should be two. The bolt when tight should not compress the washers. A small gap is desired. The purpose is to allow minor movement at the bushing inside the black boss) without the black boss striking the aluminum plate. It could also be that the bushing is worn out or missing. It could be replaced by having a machinist cut new ones (nylon rod/tube would be a good choice but there are many options of varying hardness). The bush can be three piece with a bush and two washers or two "top hat" bushes with integral thrust flanges. This type of engine mounting is typically for racing and has no bushings at all if the transmission is also solid mounted. Otherwise, damage can occur to the transmission tail housing.

[MV8]

A pic may help to clarify. This is what I would expect to see but it can vary. Some compliance with using rubber washers and a bush would also allow for some misalignment/tolerances if everything is not squared.

[bball7754]

MV8 - that is the setup, incorporating the large machined hat.

 

So the length of the unthreaded portion of the bolt shank should be slightly less (1/16th ish?) then the total length of the washers, bushing, and the plate.  This will allow the nut to be tightened against the non-threaded portion with minimal compression (almost none) of the rubber washers, allowing them to retain their full dampening properties.

 

[MV8]

Yes. That is the practice/idea with using the longer aircraft bolt, but it could be threaded all the way to the head with no unthreaded shank and still be fine. The bolt is just a clamp for the steel sleeve/metal bush/machined hat, to float on the chassis tube via the soft bush with rubber washer thrust bump stops.

[bball7754]

So I think the issue with the replacement rubber washers was that I over tightened and compressed them, which led to them disintegrating.

 

I’m not totally comfortable with only relying on the friction of the nylock preventing the nut backing off.  As long as the unthreaded length is slightly longer, I can test fit just the plate and add one or two thin washers to allow me to tighten the nut, but not compress the rubber washers.

 

The original washers were less compressible than the rubber washers, and were more able to withstand my incorrect overtightening.

[MV8]

Everything red is fully tightened by the bolt and nut to where it does not matter if it is a lock nut or regular nut. The nut should not run out of threads.

 

If there is not enough clearance when tight, the metal bush/sleeve/machined hat is too short or needs deeper machining of the hat integral washer. A small od shim could be fitted or the machined hat replaced with a washer and longer bush/sleeve.