Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Steel Sprocket

Supermax advise in BOLD capital letters "Do Not over tighten The Belt".

Mine has done 18000 miles with the belt pretty slack. As long as it doesn't jump a tooth on hard acceleration it's tight enough.

My ali sprocket had only done about 1500 miles.

Morgan set up the drive belt tension VERY tight. They do this in an attempt to minimize vertical movement of the NVH mounted bevel box which can move quite considerably, especially on power take-up. A more usual/correct belt tension allows for a 45 degree twist of the belt.

As an aside, Supermax are insistent on their pulleys being used with a low belt tension.

Forgot to mention, I don't have the NVH kit.

It's a fine line we walk with drive belts. Too tight, just right, or too loose.

Too tight can wear the pulley and belt and also create some unwanted noise.

Just right is somewhat subjective. In the Harley world, and suggested many years ago on this forum, in mid belt being able to twist it 90 degrees is about right. There's also the deflection method, but in the case of the M3W, there really is no reference to the amount of deflection based on a certain pounds/kgs of pressure. I have a couple spring tension devices that will measure the deflection at a certain amount of force. But again, twisting the belt is probably about the closest method of tensioning. AND yes, they do feel very tight even with that method.

Too loose. I know that if they're too loose to a point that they can jump teeth, but that does have to be very loose to do that. But the main problem with running, in some cases too loose, is that if the Polychain lugs are fully seated on the sprocket teeth, there's a straight pull force on the belt and that's good. But when you run too loose, the belt tends to climb the lugs out of the teeth and that creates a mechanical advantage between the two and puts WAY too much force on the length of the belt when the teeth climb with that leverage. Many Harley belts have snapped by running too loose and with the belt climbing out of the sprocket the stretch force on the belt is tremendous.

I know Supermax has lots of experience and knows their product inside and out, but again, running loose is very subjective and borders on letting the belt climb the teeth of the sprocket putting way too much tension force on the belt. Those that have the Supermax sprockets have surely by now developed a technic to get it right as 18000 miles is very nice to say the least.

I'm just throwing this all out there to possibly add just a tid bit more information and help make good choices.

On Harleys, the belt pivot point is forward of the swingarm pivot, so from time to time with loading and unloading of the rear wheel when riding, the belt tension does vary some. But as it appears on the M3W, the centerline of the swingarm and the centerline of the BB is about the same, so once tensioned, the belt tension will not vary much at all during use, regardless of weight load.

Sorry if I'm being redundant in this post, but you all have to be careful and follow proven setup practices from other M3W owners. Experience is worth its weight in gold. Bad experience, don't repeat, Good experience becomes the norm!

I hope you are all staying safe and healthy in these very trying times!

Dan

Just to follow up on what Dan has written about the concentricity of the swingarm pivot and the bevel box sprocket; on my first chassis (late 2012) it was very close to concentric so very little change in belt tension with swingarm travel, the second chassis was much the same but with my current chassis there is a little bit off a gap between the centres so the tension does change as the swingarm moves. My chassis is a slightly odd hybrid of the later type with welded in front bracing but with the earlier, solid bevel box mounting. I suspect that the rubber mounting for the bevel box may increase the gap between the centres so there is a greater change in belt tension.
Incidentally, in bike chassis design the offset between the centres of the swingarm and sprocket centres is deliberately played with in both distance and height as it affects the way the back tyre finds traction under power. Various bikes have tried the concentric arrangement but it generally hasn't led to good handling though chain life might be good!

Adding my two bits: I went through 3 aluminum sprockets and was the first to jump to the SuperMax. I was very happy with that and it did quite well. It imploded after 19,000 miles as whatever they used to bond the resin to the wheel did not hold up and the little bolts that are used to increase the bond failed one at a time. When I removed the sprocket most of the bolts had worked out and bent over and a few were just gone. The bolts they used are very small due to no room for anything bigger. Small steel bolts tapped into a soft aluminum rim are just a time bomb waiting to happen. Maybe they have improved the process. The middle of the belt showed a bit of damage due to the bolts sticking up but we kept it as it is still stronger than s**t. When that happened I just gave up and went for the steel sprocket as that was finally being offered. No noise and I don't think about it.

From what I understand from their email. Morgan spares will send me the new sprocket and I'll send back my old one.

Good News
I've one steel and No problem since despite 30000 miles

Those little bolts are actually nothing more than grub screws. I noticed one of mine starting to come undone after running for a while so removed them all and re-fitted them with some glue on the threads. No problems since, although I haven't done 19,000 miles on it!

There is an alternative to the factory steel item and one of the chaps on here - Fabian Corona - made a number of beautiful billet steel versions, one of which I was fortunate enough to purchase. They weighed something like 3.2kg (little more than the original alloy version) and would have worked perfectly well as a mantlepiece ornament, such was the machining quality of the thing. It's been on my car for some 10,000 miles and has no signs of wear whatsoever. If you search the Forum for his name, then you are bound to come acorss the thread where he told us about his (possibly one-off) efforts to do a proper engineering job on the item. Fabian was in France I believe.