4 replies to this topic

[cooperbloke]

Good morning all. It's been a long time since I’ve posted in here, but I do constantly use it as a reference. The assembled knowledge base in this forum is amazing and sets it apart from others. Thank you.

 

With that, I would like some guidance myself now please. I have built a 1299cc Cosworth BDA ‘screamer’ on a modified remote-type Jack Knight dog box using an original one piece Gordon Allen steel crankshaft. Both the engine and the gearbox have been fully checked and rebuilt. Over the summer I’ve installed it my spaceframe Mini and now I’m struggling to get the clutch to fully disengage so I can cleanly select a gear. I know it’s a dog box so ‘on the move’ selection may need to be aggressive, but I can’t disengage the clutch to get first (or reverse) to get moving.

 

Here is a list of the equipment fitted and the efforts I’ve taken to get the clutch to disengage sufficiently. The Mini has an adjustable Tilton pedal box. The clutch pedal stop screws are set for maximum stroke.  This pedal box was working well with the previous A-series engine and rod-change 'box. The clutch arm, bearing carrier, both clutch arm clevis pins and the slave cylinder are new. I’ve fitted an adjustable clutch pushrod and it’s set so the CSC piston is fully retracted for maximum stroke. The throw-out nuts are temporarily backed out (so they have no influence on max clutch operation.) I’ve adjusted the clutch arm stop-bolt to have minimal clearance for maximum operation. I’ve bled the clutch – there’s no air in system. In fact, the clutch arm operates immediately with no ‘slop’.  I’ve spaced the bearing on the carrier away from the cover so there’s minimal clearance to the diaphragm bearing plate. There was originally a 9mm gap! 

 

The following do not have any bearing on clutch operation, but I found them interesting enough to share. The flywheel on the crank relies on the taper only – there is no flywheel keyway. The taper on the crank and in the flywheel centre are unique and not the same as a standard Mini taper. The arrangement does not have a ‘C’ washer or thrust plate for the primary gear. This unit was originally competitive in motorsport in Sweden ‘back in the day’. I bought in UK but had been fully dismantled.

 

My feeling is that the machined height of the three ears on the pressure plate may need to be adjusted, but I'm inclined to think it must have been correct at one point in time. I'm confident the parts I have are all original to this engine and 'box, but I can't be sure there was nothing missing...

 

Does anyone have any more suggestions? Happy to provide any additional photos if required.

Thank you in advance! 

 

Steve

 

 

 

 

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[Spider]

Lovely bit of kit !!

If I can suggest a starting point here, measure how much movement you are getting on the backing plate, plenty of places you can do that from given your set up. You need a minimum of 1.0 mm. When everything is new and tip top on a stock Mini, they get just on 1.5 mm. If you are running a paddle type Clutch Plate, you can get away with less.

This will help guide you where you need to look.

Given that you're essentially using the flywheel fit (it seems) on the taper to set the primary gear end float, it maybe that the primary gear is getting pinched.

[cooperbloke]

Lovely bit of kit !!


Given that you're essentially using the flywheel fit (it seems) on the taper to set the primary gear end float, it maybe that the primary gear is getting pinched.

 

Thanks Spider! 

 

That is a very good suggestion. When I got it back, the machine shop had cleaned up the flywheel taper - it looked brand new. 

I wonder if they took sufficient material off that the flwheel is now fractionally closer and has indeed pinched the primary gear. Even the slightest pinch would cause it it to drag and give me the disengagement concerns I have.

 

Thank you my friend.  

[stoneface]

Hi Steve,

Good to see you're making progress. You might remember me as I emailed you with oil pump and thrust bearing advice.

Although my mini is using a standard mini taper I too don't have the standard C and thrust washer.

I have a bronze washer between the primary gear and inside face of the flywheel.

The thickness of this bronze washer took me many hours to obtain with consistency.

I torqued the flywheel many times and set the primary end float with plasti-guage. It took many goes until I was happy that the end float would be as required when torqued up. It doesn't take much difference for the end float to be reduced.

The first engine of this type I built suffered primary drag which got worse as the engine warmed up and the thermal expansion reduced the end float.

Not saying this is your issue but worth considering.

Edited by stoneface, Today, 12:52 PM.

[cooperbloke]

Hi Steve,

Good to see you're making progress. You might remember me as I emailed you with oil pump and thrust bearing advice.

Although my mini is using a standard mini taper I too don't have the standard C and thrust washer.

I have a bronze washer between the primary gear and inside face of the flywheel.

The thickness of this bronze washer took me many hours to obtain with consistency.

I torqued the flywheel many times and set the primary end float with plasti-guage. It took many goes until I was happy that the end float would be as required when torqued up. It doesn't take much difference for the end float to be reduced.

The first engine of this type I built suffered primary drag which got worse as the engine warmed up and the thermal expansion reduced the end float.

Not saying this is your issue but worth considering.

Hello again 'Stoneface'! 

 

I certainly do remember you - your advice about 360 degree thrusts and oil return lines was invaluable during the build - thank you so much.

I feel I should have anticipated this primary gear issue, but now that both you and spider have suggested this possibility, it makes sense. 

 

Thank you. I'll let you know how it goes!