Confused of Norwich writes on the subject of coupling gears

[simon.holyfield]

Folks,

I may be being daft today, but I am getting ready to fit my coupling gears. I rather thought the 'pusher' provided by Drags would attach to the crankshafts and would allow me, with the aid of the puller, to draw the crankshafts through the coupling gears.

The mystery is that the pusher has no thread that matches the crankshafts, and indeed, the thread on the front & rear shafts is different.

Am I missing something?

[nevhunter]

Anything you do in that line will require the use of the threads on the end of each crank. can you make a tool using old damaged nuts and extend a threaded portion to pull the shaft through with. Nev

[simon.holyfield]

As I thought, the pusher has two large nuts machined to fit the crankshaft threads, which are visible when you take the tool to pieces. Wish I'd done that before I posted this question!

As Mrs H is always telling me, it pays to use your eyes, ears, and engage your brain before you open your mouth!

[MARK.WALSH]

I just bought one of these and i also was scratching my head on its use
If you look carefully there are 2 types of thread, one matches the crank, so I assume you lock it in with the crank retaining nut. Have not tried it out in anger yet as im still stuck with a completly dismantled engine on my rebiuld (just spotted a hairline crack in the end cap of a con rod)....more money!
Mark

[nevhunter]

Not too difficult to make a new cap out of a suitable bit of alloy. Nev

[malcolm.johnson]

On the subject of coupling gears, happily I have got passed the assembly point and have done about 200 miles with my newly finished iron 4G. The engine is smooth and runs well, but I am struggling to accept that the coupling gear noise is ok. In an article and road test (Classic M/C Sept 1990) the writer says " The muffled sound of mashing coupling gears was slightly disconcerting,.....". Is that a general description of what to expect in the way of noise? For such a lovely engine to be spoiled by that "corn mill" sound seems alien to me. The gears looked good and damping discs were replaced. Are there any ways of improving this?

[nevhunter]

The original gears are ground to final finish. This is the only way to get a good fit, as there is always some warping with heat treatment to harden them. Backlash in the gears is the cause of noise. Any wear will make this worse and the engine cases expanding when hot will make it worse also. You could go to a lot of trouble and not get it perfect. Nev

[john.whiting]

Straight gears are allways noisy,you have to go to helical gears for silence.Some truck gearboxes with straight gears actually make a screaming noise when the gears get slightly worn.Its caused by the sudden tooth contact as the gears mesh.Then theres also rattling at idle to put up with.Regards John.

[simon.holyfield]

Basically it's a robust, low cost installation. The gears are strong, easy to make, you don't have to deal with axial loads - but the price you pay is the extra noise.

[brenton.roy]

Straight cut gears are the preferred racing option. Also, there's that awesome square four whir...
I don't think they should 'mash' though. That sounds a bit harsh. Whir yes, rattle, a little..
They may bed in a bit Malcolm.