Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Bevel Box Noise Survey

First I apologize for the length and the rambling on and on and on... Sorry there I go again!

Laurens,

I agree with you 100%...

There are two issues here, getting a proper belt tension and a loud BB.

Some here think that the two might be related.

Having the correct belt tension checked and set first will let one rule out the belt as the culprit and then concentrate on the BB noise.

There were thoughts that an overly tight belt could be causing the whine in the BB, but in my opinion that's doubtful.

As most here, I believe that there are internal BB issues that are causing the whine.

In my industry, we use recirculating ball screws and nuts to move carriages back and forth with servo motors, really fast motion.

When we started on a new product line we ordered a screw and ball set with a certain thread pitch. We had several options all for the same diameter and thread pitch. The pitch is how far we move the carriage in one revolution of the screw. With this setup we can control the start/stop position with servos to within +/- .010" at very high speeds.

We opted for the cheap version and quickly found out why it was so cheap. The finish in the thread grooves that the recirculating ball bearings in the nut ride on were not micro polished. It lasted for all our testing and was not a wear issue, but boy did it whine while moving.

On our first production machine we purchased the more expensive screw/ball combo and it was whisper quiet.

My point is that if the Quaife box is properly setup, gear depth, gear alignment, backlash etc, if the teeth are not finish polished to the inth degree, it will still make noise. Maybe Quaife has elected to not fully polish their gear sets as racers may not care if there's a noise as long as the gears don't wear out or break. Things expand when warmed up and the "possible" combination of less than micro polished gears and increased clearance when warm, you get noise.

I would be very interested in what the other member finds out with his BB after the expert takes it apart for review and setup.

The bottom line is this, none of us know what the problem is...

We're only speculating based on previous experience with similar types of gear sets, differentials and other final drive assemblies.

Only Quaife knows what's making the noise. My guess is that they're well aware of it. And it seems like even new BB's make noise, but do eventually wear in like Ken says his has. But still, how many people would approve of buying a new Mini and have a noise in the drive that "may" quiet down after a 1k miles or so. I think there would be a recall or they would not sell many as soon as the word got out.

Now we have Mark Evans active in this thread can we get a Morgan answer to..

A. The correct fill hole on the bevel box.
B. The volume of oil it should hold in ml.
C. What oil the factory are putting in it and telling dealers to use.
D. The oil change interval.

A data-point following Mark's instructions - applying 7.5kg force with a spring balance to the lower run gives about 10mm deflection on our early 2012 example - suspect this is outcome of ~1000miles driving since being full reassembly at the factory for a new chassis. Rear sprocket is well worn but the belt is not showing any sign of jumping.

Thanks Dan.
always interesting to hear from a proper engineer.

I do believe that the M3W was rushed and that the younger designer involved was not up to the task.

MMC are now almost where the car should have been at launch ...but not quite.

I have not had any issues with belt jumping or the like, but is quite loose. Can easily get more than 10 mm deflection of bottom run.
I did notice yesterday as I was starting to prepare for bevel box removal that the bottom belt was very close if not actually touching part of the frame.
When fully jacked up it very definitely fouled the frame.
This might complicate any deflection testing
Mine is a early 2012 model, lowered at front to level off the steering arms.
When I reassemble I will look to be a bit tighter.

Sorry Dan wasn't criticising your post, just making a point regarding accuracy of centre line alignment.

It seems likely that MMC did originally intend the BB box to be accurately aligned with swing arm pivots since with a clean design sheet there would be little credence in not doing so. As production changes have been made though, particularly the retro and production isolastic mountings, then maybe a small amount of mis-alignment has crept in, hence Laurens findings.

Richard, no problem on my end. Thanks.

lets all buy a belt tensioner,preferably the same!!...on amazon a H-D tensioner costs £19.We can then make proper comparisons&get it right once&4all!

Just can't get myself motivated as I'm 99.99999% sure this is totally unrelated to belt tension. By nature, the myriad of people in here with BB noise have varying belt tensions. It's obviously heat related, and I doubt heat itself is the cause...all diffs get hot. It has to do with bearing support (or lack thereof) and/or the finish/cut of the gears.

I agree, Ken.But an optimum belt tension must be estabished by MMC & the the only constant way to measure this is with a device easily available to us all....but that is another thread.