Twist throttle, hall type, advice on how to fix them

Hi, today I (with some help) managed to brake my second half-twist throttle. It's an em3ev model, lovely feel, the one that has the 3-speed infineon switch and cruise. http://em3ev.com/store/index.php?route=product/product&path=41&product_id=91

Both have broken in the same way and I think it's fixable. I borrowed the bike to a collegue to take a ride and he kinda panicked and after accelerating, in order to brake in stead of releasing the throttle and press the brakes he just over-untwisted the throtle body, like to brake with the throttle. I heard a crack, plastic-crack-type.

The way the throttle works now is fine unless it's released (like at zero volts) and on what is supposed to be zero it sends something like 1/3 throttle signal, or close to that effect. The follwing situation occurs: I brake/stop at a light, release the throttle and the bike jumps ahead from under me ; it can be solved by cutting the power at each light, but it's anoying... Today I borrowed the bike again and the second throttle started doing the same as the above, while the throttle seems to have a bit too much play.

I have two questions basically, do you have any advice on how to fix/debug or have you seen this type of 0=30% throttle fault?

drebikes said:

Hi, today I (with some help) managed to brake my second half-twist throttle. It's an em3ev model, lovely feel, the one that has the 3-speed infineon switch and cruise. http://em3ev.com/store/index.php?route=product/product&path=41&product_id=91

Both have broken in the same way and I think it's fixable. I borrowed the bike to a collegue to take a ride and he kinda panicked and after accelerating, in order to brake in stead of releasing the throttle and press the brakes he just over-untwisted the throtle body, like to brake with the throttle. I heard a crack, plastic-crack-type.

The way the throttle works now is fine unless it's released (like at zero volts) and on what is supposed to be zero it sends something like 1/3 throttle signal, or close to that effect. The follwing situation occurs: I brake/stop at a light, release the throttle and the bike jumps ahead from under me ; it can be solved by cutting the power at each light, but it's anoying... Today I borrowed the bike again and the second throttle started doing the same as the above, while the throttle seems to have a bit too much play.

I have two questions basically, do you have any advice on how to fix/debug or have you seen this type of 0=30% throttle fault?

Click to expand...

Sounds like one of the magnets inside the throttle has become adrift from its fixing point.

If you carefully take it apart, you will find a small piece of black plastic inside. It is the stop where the magnet stops. the piece is right at the edge of the tree way switch. you need to glue it back in place. Then you need to put a piece of rubber behide the stop so it doesn't break off agin.

it took me an hour and 2 broken throttles to find the problem.

it is very fixable, take you time opening it.

Dan

Thanks for the replies. Here's what happened and a fixing guide just below. I haven't found magnets in the throttle body, so the next thing obviously was a bit of plastic that limits the race of the throttle - it was bent backwards, see pics.

This leaves the throttle go further back than it's meant to; now I know it's broken, but the failure mode seems a bit severe - a bit of broken plastic to put the throttle normally-closed when it's supposed to be normally-open. One may say it's a bit dangerous, but let's not over-think it.

Be that as it may, here's how to fix it

1. Disassemble the throttle body. The easy way I found was to remove the two Phillips screws that hold a cover behind the 3speed and cruise buttons, remove the cover and jam a flat head screwdriver to push the grip off the body of the accelerator. A word of advice, be careful against what you jam the flat head screwdriver, don't put it against the Hall sensor, there's some space around.

2. Initially the broken plastic tip looked like this. It was the same on both my throttle bodies, but on the other it was completely sheared:

3. Plastic tip jammed up and supported in the back with matches. Yes, I've put a wooden peg to hold the thing and superglued everything into place. The last part will be to trim the matches down to assemble the throttle back


Hope it helps. I've tested the fix and it seems to work, there's no throttle signal on the signal wire on what is supposed to be the position zero. I guess we'll see how the matches hold in time; in an ideal world I'd 3D print a part to jam the plastic into place and add some rigidity to the structure 8) One should preventively modify their new throttle by filling up the hole behind the plastic bit

Maybe you're too 'enthusiastic ' using the throttle? If this were a general problem there'd be more broken throttles.

alsmith said:

Maybe you're too 'enthusiastic ' using the throttle? If this were a general problem there'd be more broken throttles.

Click to expand...

I don't think so. The tab that broke off has no support to take the shock, from full throttle and let go is a snap ad a shock to the stop.

Like driving a car. Do you slowly raise your foot and then step on the brake when a car cuts you off? No you move quickly from the throttle to the brake, so the throttle snaps back to a stop.

I havn't broken any other half-twist in the same way. Shifted a magnet but not broken plastic stop.

I am sure this is not a design Paul made, just what is out there and fits the system. As I said I broke two and since reinforcing the reglued tab it has been fine for about a year now.

Dan

I had the same problem and super glue managed to fix it for a small while, it broke again after few weeks

The key seems to be filling that area behind the broken part- a nice big puddle of epoxy to support it would be good. Superglue has never been very good on plastic ime

alsmith said:

The key seems to be filling that area behind the broken part- a nice big puddle of epoxy to support it would be good. Superglue has never been very good on plastic ime

Click to expand...

Agreed, you need to offer some sort of support to that plastic bit, because once broken/glued it would be even weaker than it was at the beginning. I filled it with wood and drowned it in superglue so it's solid. The idea with the epoxy is far better, I wish I thought about it.
A side benefit of epoxy-filling is waterproofing. After filling the hole there was superglue dripping near the 3-speed switch, tiny hole, which now is filled with glue. Some said there are issues if wet, well filling that space in th ethrottle body with something should make it more water tight.

It's not Paul's fault for this design, far from it. He sent me a replacement right after the first one broke, so no complaints from me. This fix just allows me to avoid waiting for the shipping from Singapore for yet another replacement.

@alsmith: yes, those that broke it were clearly too heavy handed, but like with the Iphone4 antenna design fault, you can't just say "you're using it wrong". The purpose of this thread is showing that spending 5mn to drip in some epoxy can make this throttle quite a bit tougher than it is by default.

would this epoxy work?
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=61492

it does not have to be epoxy. dan observed, and you should use the info, that the critical thing to do is to reinforce the broken tab with the matchsticks or other material to keep it in place when the throttle rotates back against it.

you could use other material for backing. you could even use wood glue on these match sticks. you don't have to use wood either, it could be another piece of plastic cut to fit the space. then you could use contact adhesive to hold it in place. i prefer contact adhesive on plastic.

Actually my goal is to make it waterproof. I had 3 throttle failing within a week due to british weather

Just about any epoxy will work. But it sure makes impossible to change the 3 speed switch then.

I have the same problem with the switch, chaned settings so the setting I want most is in the middle. thhat setting is default whan not connected at all. You even can switch the wires around at the plug to get that setting.

Dan

cwah said:

Actually my goal is to make it waterproof. I had 3 throttle failing within a week due to british weather

Click to expand...

Just give it a good spray on the inside with a good silicone spray or pack it with silicone grease (even better)

gwhy! said:

cwah said:

Actually my goal is to make it waterproof. I had 3 throttle failing within a week due to british weather

Click to expand...

Just give it a good spray on the inside with a good silicone spray or pack it with silicone grease (even better)

Click to expand...

I don't think silicone spray or grease work as it release acid while curing that attacks metal.

cwah said:

gwhy! said:

cwah said:

Actually my goal is to make it waterproof. I had 3 throttle failing within a week due to british weather

Click to expand...

Just give it a good spray on the inside with a good silicone spray or pack it with silicone grease (even better)

Click to expand...

I don't think silicone spray or grease work as it release acid while curing that attacks metal.

Click to expand...

no not that sort of silicon .. the regular silicon based grease it dont set same with the spray

cwah said:

Actually my goal is to make it waterproof. I had 3 throttle failing within a week due to british weather

Click to expand...

cwah, out of curiosity what broke due to the water? Something shorted or corroded? (Northern) French weather isn't much better than UK's, maybe I just got lucky until now? Or them being watertight is a byproduct of the match+superglue fix I did earlier...