Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Timing belt trouble

I am sorry but having had the rear end of my M3W severely smashed at the beginning of this week, I am just a little touchy.

I just thnk it would be feasible and I have started to lay it out in AutoCad. I have also bought a spare camshaft support plate, camshaft pulley and crankshaft pulley from Matts Machine Shop to get the dimensions of hole centres, pulley bores and angular positions of keyways etc.

Despite the various doubters I will still look into the possibility of doing this gear conversion as long as the cost is not too prohibitive.

Well.. You have the extra time now...

If you decide to go ahead might it be worth considering lubrication of gears simply by using oil leaking past camshafts rather than a dedicated pool of oil, which may cause drag?

It's a while since I've worked on Guzzi engines but from memory the timing gears illustrated in earlier post, received lubrication in that manner since the was no camshaft oil seal. The dribble of oil then made its way via gears to bottom of chamber where it drained back into the sump via holes you can see.

A recent warranty job to cure leaking camshaft seals on my car indicates there is oil behind, so removing them may achieve the purpose, although not the double lip crank seal which may be holding back some oil pressure. Anyway just a thought.

Thank you Richard for your comments on the lubrication of the gears.

The arrangement I envisage will have 3 idlers, i.e. 1 between the crankshaft and the inlet camshaft and the remaining 2 would replace the current rollers that sit above the camshafts.

I intend to run these idlers on needle roller bearings mounted on fixed spindles, the outer ends of which will have an "outrigger plate" that supports their outer ends, (similar to the Vincent set-up).

The idler spindles would have an oil hole down the centre to feed oil to the needle rollers and this would be provided by an oil feed to each spindle, mounted in the timing cover and fed by a small jet in a line tee'd off the oil pipe returning the scavanged oil to the tank.

I believe that I am correct in saying that the oil pump scavanges oil from the camshaft cavity and not from the sump.
If this is the case and the timing cover is made oil tight, then possibly a hole could be made low down in the camshaft support plate to allow any oil building up in the timing cover to drain across into the camshaft cavity ready for returning to the tank. This drain hole would be below the crankshaft gear and therefore excessive oil drag would not be a problem and the gears would be lubricated by oil exiting from the idler needle rollers.

What do you think of this arrangement?

Sounds good, the needle rollers shouldn't need too much oil. Ironically I was just musing over your proposed mod and scribbled a layout to check for correct rotation. I came up with exactly the same for a gear wheel count of seven.

Since this would (maybe) allow you to use existing idler pivots, is this what you intend?

Is it possible I wonder if S & S originally designed engine with geared timing as an option.

Not sure where scavenge pump sucks from - where the most oil is I guess.

Because of the size constraints and the size of the gears I intend to use, the centres of the 2 upper idlers do not quite fall on the same centres as the existing tapped holes for the roller spindles.

There is however, sufficient meat in the bosses on the support plate for them to be drilled and tapped slightly off centre for the idler spindles.

The central idler between the crankshaft and the inlet camshaft will run on a spindle this is mounted in the area currently occupied by the spring tensioner device. The plate is tapped 7/8" UNF (14 T.P.I.) and i have made up a threaded plug to fit this thread which I have loctited and pinned in place. This plug will then also be drilled and tapped to take the idler spindle.

Note:- As the idlers will all be running anti-clockwise, they will all be screwed in using a left hand thread so that the natural tendency is to always tighten them up when the engine is running.

You have certainly put a lot of thought into this. Regarding exhaust cam idler location is there any leeway there since you don't need a specific number of teeth? Maybe you could be cunning here and arrange for hunting teeth by having an extra one, and so even out wear as per Velocette practice, although timing marks only align every x numbers of rotation then.

BTW had a look at exploded diagram of X wedge engine. It appears that the bottom of camshaft chamber is higher than that of crankcase. This would leave a certain amount of oil in bottom of crankcase if the scavenge suction point is in the former, but this may be by design. I note there is a magnetic drain plug in sump as well.

What I have never heard it explanation, however speculative, of why these belts seem to be fine when these engines are used in a motorcycle frame, yet they seem to have a very short life when used in the Morgan. You would think with the engine sitting up front and that time in case exposed to the wind that if anything it would be running cooler than it would be sitting out the side of an air cooled motorcycle. I don't know if any of the armchair Engineers here on the board have an idea about the actual cause of these failures.

I don't think the cam belt problems with the S&S X Wedge engine are restricted to the M3W installation, there have been problems in bikes as well I believe. Just off back to my armchair now.


http://www.bigdogbiker.com/threads/another-x-wedge-cam-belt-shreds.40080/

Absolutely correct, even Hesketh have had to put a vent into the cam belt area to provide some more cooling.