Manky Monkey Motors

Decided to have a go at making an internal throttle. Partly because I'm to tight to buy one but mainly because I feel, most a too complicated.
The design is based on the old Honda one, (simple but let down by poor material selection) Has only two moving parts, the slide and the twist grip
and requires only one screw to hold it al together.
Usual disclaimer- This might not work. :P

Started with the slide, made from bits of brass scrap. The original Honda ones were a soft alloy casting and wore badly.

These have now been blind riveted together using copper pins until I get around to brazing them together. I used copper because one will have to be drilled out later.

you cant leave us in susspence like this you know

 ::)
I post as I go along. That way if I balls it up you will get to see that too and hopefully someone will tell me if I'm going wrong before I make a complete ass of myself.
It may not look it but the slide has so far taken a couple of hours to shape.
Once brazed it will have a diagonal cam slot cut across the top to match a spiral that will be inside the twist grip tube.

Getting it wrong.  :P

Starting to look complex...good luck .. Lol

Trying to get the pitch correct on the spiral is a pain but first try I even had the helix going in the wrong direction  :-[
Worked better second time around and have cut the slide to suit. Should be able to get the slide finished tomorrow by drilling and slotting to take the end of the cable.

Really looking forward to seeing this done :)

Me too  ;D
Apart from some smoothing out this is the finished slide.

The outer cable stop/guide.

A beautiful job as always Dave. I wouldn't know where to start, attempting to make one from scratch.
I picked up a Honda one from an autojumble once, intending to use it on my Reliant trike, but the throttle didn't turn far enough to fully open the Reliant's SU carb.

Yep that's always the problem.
Even doing it myself, have decided not to try to get the full travel at the twist grip, as it steepens the angle of the helix. This makes the throttle harder to turn and increases wear. Instead I plan on altering the length of the lever on the carb.

Throttle tube made along with the end bearing bush. Forgot to take a pic of the bush but basically a plain bush with two grooves in the OD that the grip tube has been roll crimped into. This will also be soldered into place.
The helix has already been soldered into place.

So you fitted the screw, (Helix), inside the twist grip tube by drilling through the tube & soldering from the outside?

Nope. Soldered it in place by standing the tube on end (the spiral is a very tight fit so stayed in its correct position), heating with a gas torch and applying flux then solder to the top of the helix. Gravity and capillary action meant the solder ran all the way down the spiral. Simples ;D

very smart

He's a clever old sausage is Dave.

Handlebar section/slide guide.
This took a while.
Starting with a solid bar 19mm Dia, the spigot was machined first, then the bar was bored out 10mm Dia. to depth. This leaves a 4.5mm wall which should give plenty of bearing area for the slide. Not having a mill meant that the slot had to be done the old fashioned way by drilling holes in a line then grinding and filing then burnishing out the rest. The spigot at the end is drilled and tapped to take the twist grip retaining screw.

IT WORKS  ;D 
Temporarily assembled ( but not welded ::) ) on a piece of tube left over from making the new bars.
Just over 1/2 turn (190 deg. ) gives about 35mm of pull which should be enough. The grip tube has been scored to ensure good gluing of the rubber grip.
Not my prettiest work but you wont see any of it.

That's good news, when are you going into production ;D

yep think there'd be a market all right

No way. Too much effort and I'm supposed to be retired.  :)