Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 This really bothers me...

I suspect it is subtle changes in the amount of backlash in the gear mesh. My Ducati has helical cut bevel gears that were lapped at the factory and have to be shimmed to the same minimum clearance as they were set up to at the factory.

It costs money to lap in and shim precisely gears.

Gears whine because the gear faces are hitting each other taking up the clearance differently as the gear rotates. Round is not always perfectly round.

If the clearance is less, and you are lucky with nicely matched gears, then the box will be quieter, but still whine. Too much clearance and you get clatter on neutral throttle which is the noise of the gear faces slapping against each other on each side.

Straight cut gears hit across the whole straight width of the gear providing a wide contact line that does its best to roll around the involute form of the gear surface, whilst helical cut gears slide against each other along the length of the gear; so its a softer transition of forces. Hence less noise, but weaker gears.

(So, the cheapest and easiest solution for everyone would be if Morgan swapped the whining bevel boxes before they left the factory. It would be less waste of resources all around.)
I like that & hope thats what happenes before i get my m3w,because i want them to also do the first service before it gets shipped to kuwait.

I would have thought it was more expensive to deal with warranty claims, and it still doesn't explain why some do not whine from the get-go, while others do. Unless, of course, the designed-specifically-for-the-M3W-bevel-box is manufactured with such sloppiness that it truly is like a lottery. If so, perhaps Morgan should ask Quaife to up their game and be more precise with their cnc routing.

It should be, as it's CNC'd. It can certainly be done, and I very much doubt a big company like Quaife doesn't have the machinery.

In other words, it's down to pure luck, and lapping the gears won't do, as you first suggested. Seriously, we live in an age of CAD design and CNC machines which can take the cad files directly. It can be much more precise than some guy in a shed, and it is now down to "luck"? It may be, but it shouldn't be. Bevel boxes are everywhere, and it's not exactly cutting edge technology having a bevel box. Hell, Ducati and Harley Davidson have bevel boxes. Yet you don't hear them having whining bevel boxes to the extent that the M3W seems to have.

Yes, and all this should be no problem for a company like Quaife to take into account in the design and CNC cutting phase.

What I'm saying is that it doesn't matter how many potential problems you can list. The fact of the matter is that 1) bevel boxes work without whining in other vehicles, 2) Changing bevel boxes under warranty for what may be another faulty one (if it truly was a matter of luck) cannot be cheaper than doing it properly the first time around, and 3) A company like Quaife ought to have the knowledge and machinery to fabricate a bevel box without the whine. But as it's down to luck, perhaps they can't and it's impossible to do.

So, the cheapest and easiest solution for everyone would be if Morgan swapped the whining bevel boxes before they left the factory. It would be less waste of resources all around.

I would just like to say that i was only trying to explain why some boxes whine more than others. Not to justify noisy boxes in the first place which is clearly a touchy subject. I have had to have my box replaced not because of the whine but because of the excessive backlash causing a clattering on neutral throttle. This would have lead to premature failure of the box in my opinion. I am happier to have a box that just whines but would be even happier with a nice quiet one.

It remains a fact that Quaife are a quality OEM supplier and will supply to a specification set down or agreed by the MMC. Manufacturing tolerances are inevitable even with CNC machines and this will lead to a production spread in the amount of whine from the box.

If they want a low noise box then they should have specified a spiral bevel gear set like that used in most differentials. But that is more expensive to manufacture and any engineering project has a budget to be kept to. You are right though, with the amount of boxes they have been swapping out, it would have been more profitable to have fitted a lower noise box.

Bottom line: I knew that the boxes whined and there were problems with the compensator before i placed my order, the test car whined. I still placed my order and in the six months i have had the car it has been back to the factory twice for a total of six weeks. The problems with the compensator and the bevel box have tinged my enjoyment with worry and concern over the future. However...... and its a big one...... every time i go out and drive it, it puts a smile on my face.

In the end, that is what it is all about.