Side casing

[rossclark]

I've gone to test fit the side casing to an engine I'm building on SIL casings I got from SR a couple of years back. I've already had a couple of issues I've had to fettle on these casings. The gear shaft would not fit in the hole at the bottom of the casing, the hole had to be reamed and a couple of the endplate threads weren't tapped deep enough.

Now with the side casing it seems that the casting where the bronze push rod for the clutch goes is sat on the clutch centre so the casing rocks from side to side

Anyone else seen this ?

I presume it'll be fine to just file down the rim of this by a mm or so to give some clearance?

[Warkton Tornado No.1]

Hi Ross

With all the shenanigans encountered when fitting ‘homebrew’ extended or motorcycle clutches in casings, I’ve had to do this on occasion, but only a nat’s. I've never bought a new cover but you'll get the similarity!

Obviously, the really thick crankcase gaskets (excellent from the likes of Chiggy, if you don’t mind orange) help.

Mark

[rossclark]

Cheers.

The clutch itself is an MB pressure plate and spider with 5 of the red BGM plates in, 1.5 steels and there's plenty of separation when compressed. I could probably have sneaked another plate in if I'd been willing to put thinner steels in or fitted a couple of thicker steels and if the thicker ones I have hadn't been a bit rusty...

I think the pressure plate may be sitting a little tall but this combo is designed for 4, 5 or 6 plates, another plate might force it down enough for clearance.

I've often wondered how much clearance there was in this area and I suspected that in most cases the bronze push pad sat on the centre plate, I guess now I know it's not much...

I'll have a look at thicker gaskets before I get the files out.

[Warkton Tornado No.1]

Beside motorcycle clutches, I have used CamLam plates & steels for years but they are expensive although good quality. Prior to their availability, I used to surface grind old steel plates to 1.2 mm (or less) to fit more plates, leaving the surface deliberately roughish. It may not be the first thing in most people’s minds as we’re all a bit ‘OCD’ but steel plates (& even friction plates) don’t all need to be the same thickness, though I would advocate thinner components toward the top.

I’m sure that you are aware that absolute clutch clearance is one of the key factors affecting gearbox life.

One of the best conventional ‘fit & forget’ six plate clutches I’ve encountered is the scootRS set-ups but they are no longer available, presumably. Recently, I stripped one out of a very torquey (240 plus) engine to check & the condition was superb, though I do use a very 'non-conventional' oil.

[rossclark]

Yes the usually quoted minimum figure is 1mm of clearance with the clutch fully compressed but no-one ever quotes a maximum figure.

When I built it in the first place I used the 2.5 mm top plate but when I saw the amount of clearance it had I swapped it for a 3mm one. After which I have about 2mm I did consider changing the bottom two steels for 1.7s which would have brought the overall clearance down to about 1.6mm but I thought it better to have a bit more rather than a bit less to ensure it disengaged properly as I doubt the lever will compress it as far as the tool does.

[Warkton Tornado No.1]

The limiting elements within obtaining more clutch compression motion are the position of the internal clutch cam, the clutch arm & the handle bar lever. I don’t like a lever with a massive hand span so have had to think laterally if using ’say', Serveta dog leg levers with clutches requiring more clearance.

The internal clutch cam can be optimised in the case of the thimble type as with thicker gaskets & shims under the thimble it can be ‘tuned’ to an optimum.

I also set the clutch arm toward the back of the engine to give more angular movement (despite reading much contrary advice on Forums!) & even use shortened, welded clutch arms on clutches with more than six plates, but understand that not everybody believes this works. If you sketch it out, it makes sense. Liken it to the top end (piston @ TDC has the least piston movement but the crankshaft has the greatest angular movement) but in reverse as the greatest angular movement is desired in the case of the clutch arm.

I hope that makes sense.

[rossclark]

Found half a 1mm thick orange gasket in the bin and tried that and it seems to put things far enough to out to stop it touching the clutch. It might not be enough tightened down so I think I'll order a 1 and a 1.5 and see how it goes.

[corrado]

Mr B has posted an interesting article on FB with regards to thickness of steels and mixing them up with thicker steels to the bottom. He's even thinking of making a 2mm steel.

[rossclark]

The BGM corks must be quite thin as I've got 4 x 1.5 mm steels in no bother at all. A 2mm one at the bottom would definitely bring the gap closer to 1 mm when compressed.

I'm a little confused by the point though as he starts off talking about drag which is caused by not getting enough separation. I'm guessing that this applies in situations where you're struggling with getting the separation in the first place.

You stocking them yet Martin?