I need a foot clutch design

[lingeringstin...]

For reasons I can’t begin to go into here I need to make a foot operated clutch on an MZ frame.

MZ's don’t have a lower frame to attach anything to. The MZ frame just hangs the engine out there and there’s no undercarriage of any sort as far back as the rear engine mounts on the swingarm.

I refuse to continue using the standard MZ footrests because they are rubbish and I’ve hated them forever. They will be removed and left out of the equation. If you aren’t familiar with what an MZ TS250 frame looks like without footrests then you’re in for a laugh.

Before you say it, I can’t use the rear footpeg hangers either. They do use them on MZ race bikes but on my bike it can’t be done for several reasons and they are already being used for other things anyway. It would be too much complication to change it now, so they’re out of the question.

So, as I refuse to use MZ footrests and can’t use the rear footpeg hangers the only thing left is probably the swingarm bolt, which is about halfway between the two MZ footpeg positions so it's within reason. Easiest thing I can think of would be to make a longer swingarm pivot bolt that sticks out six inches longer on each side and use that as the solid footpegs to cobble pedals to.

The brake shouldn’t be a problem but I need to design a cable or hydraulic clutch pedal that has the capability to have the clutch stay disengaged on it’s own until I want to engage it, even without my foot on it.

The gear lever will be a simple long handle affair attached directly to the engine’s shifter shaft.

I’m thinking of modifying the five speed gearbox into a four speed by welding a blob into the selector drum so that it can’t go down past neutral, so that means no first gear. That way when you come to a halt you can engage the clutch and just bang the jockey shifter forward to go down-down-down until the last thing you hit is neutral. Then when you go, all the gears pull toward you to shift up, a bit like one of those fancy pants automatic gearboxes some sporty cars had when I was a teenager. I’ll upgrade the clutch and gear it so starting off in second gear is feasible. Not after great top speed or burnouts so I think it will work OK.

I want to make a clutch pedal that will keep the clutch engaged by itself much like old bikes used to have. The aftermarket foot clutch kits I’ve seen are too expensive for what they are and made to fit to a frame (which I don’t have any of there) and I’m having trouble imagining how to make a pedal from scratch that will stay put until I want to engage it.

Don’t care if it’s cable or hydraulic or both somehow. There may be some sort of electronic valve thingy that could be used on a hydraulic setup? Seems like I'd heard of such a thing for trike handbrake use but I don't know what they are.

There’s some waffle about foot clutches here that explains pretty much why I want a clutch that stays in position:



https://www.sturgis.com/content/blog-home/entry/no-such-thing-as-a-suicide-shifter.html



There’s some awkward traffic lights on hills that have given me some brown trouser moments more than once in the past when loaded up with camping gear and pulling a trailer to a rally. If I hit the lights at the wrong time I’m sitting on a steep uphill grade with dodgy brakes. In all other respects I like my old Yamaha TLS front brake but the one fault with them is that they are really quite shit at braking in reverse, so having to sit on an uphill slope at the lights can be frightful.

It has occurred to me that by making a foot clutch pedal it leaves the lefthand handlebar lever doing nothing. I want to keep the switchgear which is connected to the lever mount so perhaps there’s some way to use the now defunct handlebar clutch lever to do something.

[hmmmnz]

does it have to be a foot clutch??

your problem going to an old harley/indian style foot clutch as that they didnt have springs to hold mulltiple wet clutch plates together,

just disengaging the plates is easy, but holding the clutch disengaged might be considerably harder, unless to use a lock that engages when you depress the pedal, then you knock it off and release the clutch pedal as normal,


as for the frame, look at the mz500's i used to own one and they are a mz 250 frame, but with an extra cradle bolted on, to hold the big old rotax 500 lump in there.



i think you'll have to explain in more detail why you cant use the hand clutch but can use the same hand to change gear.


the obviously thing to do is run a dual lever set up, with a full sized cable clutch and a half sized hydraulic operated brake


or have a right handed clutch, and a foot brake that operates both brakes, far easier if the brakes are hydraulic then all you have to do is fit a bigger master cylinder and a bios valve
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[WD Forte]

My Old '59 Thunderbird had a 'slick shift' where the action of the gear change slipped the clutch prior to changing.
I could make something like this but I wouldn't unless it was on a trike
If you stop on a hill how can you use a foot brake and foot clutch at the same time?
Do you have disabilty that prevents or hinders you using a conventional clutch?
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[Teflon-Mike]

Initial Random thoughts:-
1: Footrests. The benly's have bosses on the bottom of the motor to take a bolt on sub-frame for footrests and side-stand.
I have chopped the footrests off at least one, n order to fit side-stand to a Super-Dream.. There-in may lie potential solution to both foot-peg and side-stand location issue.
2: Four-speeding a Benly... a) if any ratio is not needed on a 5-speed Benly its most likely top, not first. b) the 185 and 200's are already 4-speeds... box is actually a tad tougher, they have thicker cogs, and they are quite well spaced.
3: a 1930's style suicide shift.. err... yeah.. but Oh-Kay... two-foot lever of the change shaft, instead of a 2" one... have you looked at how many degrees of shaft rotation you will need? I would imagine that a lever that long is likely to need a 'stroke' like a skiff rowers, possibly begging a roller saddle to move it the distance needed! It's hardly a heavy box either! If you insist on a suicide shift; my imediete reaction would be to use a short lever pivoted on the tank, 30's style; with a par of bowden cables between rockers down to an abreviated shift arm, ala C90, to pll up and down.
4: in similar vein, with a suicide shift; imediete solution to clutch that is suggested is the old 'signal-box' lever actually on the shft lever shaft, you compress as you grip shift knob; if you wish to effect a clutch 'lock' then a latch that drops into the lever gap whe the lever is opened, and isbutto released to allow the clutch to be engaged, like a Hand-brake, would be the obvious solution...

5: Notions of hydraulic clutch, I pondered fro last post, ad believe is a bit of a dodo.. if this one isn't. Cables actually have some inherent compliance under strain, from the twists of the strands; hydraulics suff viscouse drag. Comparing clutch action on hydraulic clutch CBX750 to the cable on same engine n the Seven-Fifty, advantage of a direct acting hydraulic, IMO are somewhat mute. You don't have as much feel on the hydraulic; its no more 'powerful', or any lighter, really, and on a motor that has large amounts of torque that begs very stiff clutch springs to keep plates together... not something a Benly engine is EVER likely to be accused of requiring, even if you supercharged it and ran it on nitro-methanol! 'Problem' of heavy clutch action isn't n the actuation method, but the heavy springs, and the 'solution' to my mind wouldn't be an alternative to the cable or hydraulics or a different lever ratio as often attempted to lighten clutches on trials-chops; but a 'servo'... you are probably more in touch with NADB tha I am, but I have seen somr pretty 'neat' installations of servo-clutches on car-style single plate bikes... err.. yeah... BMW's & Guzzi's then... that have used an electric 'Weasto' brake booster/servo on a hydraulic actuation to reduce the 'holding' pressure at the lever.. but on a Benly?!?!?!? I REALLY don't think you are ever likely to need go to anything so sophisticated!

Is the engine back in one piece yet?
How far have you got as far as the motor-mounting?

Suggestion for ow, would be to look at Benly footrest brackets, and ponder whether their peg position, basically middle of the sump, would suit; and or whether to relocate off that bracket. Then as far as foot-change goes, look at the CB125 Super-Dream rear-set linkage, and possibly the Rebel or Chinky derivatve's 'forward-control' linkages; that could be adapted, pretty easily to put foot-shift lever in best proximity to peg... OR, if you persist with suicide-shift, be adapted to a twin-cable operation from a short tan-lever you wont have to push or pull into the next county to get the selector travel!
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[Pete.]

Nick a heel-toe pedal off an old clunker and adapt that. Press front for brake and rear for clutch.
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132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[-]

Most one armed racers tend to use a thumb clutch on the same side as the throttle. Sounds much easier.
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[hmmmnz]

[bugeye_bob]

what about the Rekluse clutch system?
not what you asked for I know.

[lingeringstin...]

[quote=" The benly's have bosses on the bottom of the motor to take a bolt on sub-frame for footrests and side-stand.
Is the engine back in one piece yet?
How far have you got as far as the motor-mounting?
[/quote]

Yeah I have only just now seen the unused bolt holes on the bottom of the engine. That looks like something to be thinking about regarding footpegs and whatnot. I hadn't noticed them before because I have only been looking at my bike frame which still has the MZ engine on it so I never thought about looking at the bottom of the Chinky engine which has been in bits for a while. I only got a clutch nut tool a couple of days ago so I've never been into the bottom end until this afternoon but everything looks fine in there so I've just cleaned it all up and put the bottom end back together with a new gasket about an hour ago.

The top end could use a little attention. There's a ring of crud around the bore at the top that needs honed out and I'll fit some new rings. The gudgeon pins actually look OK and I'll take the valves out just to have a look but I doubt I'll have to do anything to them.

It was supposed to be a low mileage engine from a quadbike but quads tend to get razzed to death by spotty teenagers who abuse them mercilessly and never change the oil so I wanted to take this engine all apart just to see what it looked like. Seems fine so far.

As for the foot clutch that may be too much hassle for what it's worth. It all started when somebody gave me a nice new jockey shifter they bought and then decided not to use and I've been determined to do something with it ever since. Not liking the MZ footpegs just seemed like a good excuse do some remodelling since I'm going to have to make exhaust and motor mounts and rejigger the rear wheel and brake setup to come off the other side.

The rear engine mounts are going to be modified MZ mounts and they attach to the swing arm bolt which doesn't do much as I have struts instead of shocks on the back. I have a plan to bolt a down tube to the MZ frame just behind the headstock to hang the front of the Benly clone engine from using a quadbike front engine mount welded to the bolt-on down tube, and I'll use some Honda CD250 head mount brackets things welded to the MZ frame. That will give me three mount points that should keep the engine where it's supposed to be.

The problem is that I want to do the entire MZ to Chinky engine swap in one go so as not to be off the road for long so I'm gathering all the stuff together piece at a time. I've got all the leccy and carb bits now and the engine will be back together in a few days if I get round to it so it shouldn't be too long now. I want to do it all in one day but unforseen things will inevitably go wrong and it'll probably take me a week instead, but we'll see.