Advice needed on lever effect

[tysonn]

Hoping a physics expert can advise.
I have a 1959 Morris Minor convertible that I bought in a state of half finished restoration.It had had the engine and box replaced with those from an MG Midget(1275cc).The midget originally had a diaphragm clutch hydraulically operated.The Minor had a coil spring clutch manually operated clutch using rods and levers.I can buy a manual/hydraulic conversion kit but its not cheap and I would prefer if possible to use what I already have.The conversion has been done before but it seems to make the clutch operation quite heavy and on/off in operation.I enclose a diagram of the clutch linkage.Part no:10 is the pedal assembly,41 is the rod that connects the pedal to the lever on shaft 56,the other lever on shaft 56 connects to the clutch adjusting rod 65.I have welded extensions to the 2 levers on shaft 56 and drilled holes in them so I have a variety of positions for the operating rods to attach to in the hope that by increasing the effective leverage I can give more control over clutch operation and also decrease the amount of effort needed at the pedal to move the clutch fork.
My question which (now longer) arm on shaft 56 should be the one that I use to give this effect?I realise I could just try all combinations but if anyone understands the principles properly(its given me a headache)they could point me in the right direction.
Thx
Mick

 

[rtbcomp]

Increasing the length of the lever connected to the pedal will decrease the effort at the pedal, put increase pedal travel.

Increasing the length of the lever connected to the clutch fork will have the opposite effect.

The effect is proportional to the perpendicular distance from the connection between the lever and rod and the lever's pivot.

It's impossible to say by how much you need to adjust the length of the levers without knowing what acceptable pedal travel and pressures are.

Personally I'd go for trial and error.

 

[piman]

Hello Tysonn,

The Minor clutch in standard form is light to use and progressive. Any modification that makes the pedal lighter will decrease the throw to the clutch and you risk not having sufficient travel to operate the clutch cleanly.

Alec

 

[rtbcomp]

Making the pedal lighter could either reduce the throw at the clutch as Piman says, or increase the pedal travel, each with its own issues.

The only way you'll get a lighter clutch with the same pedal travel is to use a servo.

 

[500e]

You have 2 points to fiddle with on the jack shaft one to the pedal 1 to the clutch actuation rod it is a trial & error as rtb said, there is also as last resort arm on pedal itself, have seen in the dim past a conversion with an extension on clutch operating arm.

 

[Terrapin]

Personally I would bite the bullet and buy the conversion kit. It will save you time and ultimately remove any reliability fears in the future. Just imagine that great summer road trip away from home ending because the linkage fails and it's made up of parts not available off the shelf!
You have to look at the wider picture sometimes

 

[tysonn]

The main reason apparently for clutch operation being heavier now than it was with the standard clutch is that this one is diaphragm type.It operates as it should as far as at goes its just that its more fierce now.I have read that increasing the leverage would make the force needed to depress the pedal to change gear less.

 

[rtbcomp]

That's true, but you will increase the pedal travel.

 

[tysonn]

Dont mind that as long as it reduces the effort.Thanks to all for the advice ;-).

 

[KemppiFrog]

Personally I would bite the bullet and buy the conversion kit. It will save you time and ultimately remove any reliability fears in the future. Just imagine that great summer road trip away from home ending because the linkage fails and it's made up of parts not available off the shelf!
You have to look at the wider picture sometimes

That made me smile..... The idea that there are any parts 'off the shelf' for a Moggy is a bit far fetched.

The later MMs had 1275 engines as standard, and were (are) a delight to drive, cept for the brakes being a bit feeble. Marina disks cure that, the hubs being similar, along with the suspension.

Diaphram springs are different to coils, in that the coil ones are progressively harder, while the diaphram ones get lighter as the travel passes passes a point ( usually after disengagment)

Suck it and see.
kf