Handlebar expansion plug for e-throttle repair

Joined
May 28, 2013
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120
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Ottawa
Hey Zombiez,

Need the collective sounding board on this one. (Esp. After spending the last 36 hours awake due to a family emergency - all good now but waiting in hospital rooms on chairs that are harder than the steel used here to make trikes is not fun)

I have the pictured (at the link below -I hope this works from my phone) throttle and the corresponding expansion plug shown. As you can see it is a cast aluminium thing. One leg has cracked off, two more are in danger. Why? Probably due to not enough handle bar free to accept the expansion plug without undue tightening.

Throttle

Now, as I have no idea how pure or what alloy this is, I am guessing I can try using the Bernzomatic aluminium brazing rods to make the repair, but risk it snapping again. I don't have the ability to use Al wire in my fcaw machine, but I have a wide variety of torch heads mapp gas and of course my Oxy-Acet kit.

Or I can trace the circle on a bit of 1/8" steel twice, cut and drill those out. Weld 'em up and carve via trusty dremel the friction lock flange, and a t-cross shape that folds up around the centerbolt

What seems the best answer to the hive mind collective here?
 
Joined
May 31, 2013
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3,293
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South Benfleet, Essex, England, UK
It might be that the bars you are putting it in are too large a diameter and that is the first leg of the three to object?
What is the diameter of the handlebar tube (OD & ID)?
Can you put a thin metal (one or more slices of soda-can) wrapper around the 3 prongs of the expansion plug to make up any excess so the expansion wedge doesn't need to push the legs of the plug out so far?
 
Joined
Oct 19, 2012
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1,604
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Wakefield, UK
I'm struggling to understand why a throttle uses any such clamp. I'm also struggling to understand why a piece of metal designed to expand would be made of cast alloy, a material known for having no bending qualities whatsoever. It looks like as poor a choice of material as you could possibly imagine. I doubt that there is any point in trying to fix something so poorly designed for the task.

I'd be more inclined to drill and tap the housing, if there's some metal under the plastic that is, for a grub screw like most throttles are mounted.
 
Joined
May 28, 2013
Messages
120
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Ottawa
Danny,

I'll run the vernier caliper's over the handlebar tomorrow to get the actual OD/ID numbers, the part (which answers one of Popshot's questions) is made in China, resold by Grin Tech. over at ebikes.ca It will fit 17 mm or larger ID, but not thick wall aluminum as stated here: https://ebikes.ca/shop/electric-bicycle-parts/throttles/t-htwist-slim.html

I think that the shortish length and style of handlbar on the TerraTrike contributed to my needing to really crank this tight in order to get it to make a solid purchase on minimal metal - ie, the clamps for the shifter and break pushed the inner end of the throttle a bit too far out to get good mechanical contact.

As such, I'm not certain pop can metal which is bloody slippery, will have enough surface area to lock. The fact that two other tangs have stress cracks also bugs me. I'm game to try the Aluminum brazing rod, but it's such thin stuff - 2mm, I'm not sure it'll hold up.

As to why this sort of inner clamp vs an outer clamp like the brakes and shifter's use, I'd say for pretty factor, and cost. as for a grub screw Popshot, sadly there's just not enough material to get it to anchor and lock in, this grip is maybe 1-2 mm thicker than the SRAM bar end grips that were on the trike after I had to replace the original ones, which does make it a very nice grip size for my meat hooks.

David
 
Joined
May 28, 2013
Messages
120
Location
Ottawa
Thought about it. Would it have enough friction and what is the OD? Those were my intial thoughts.

Not abandoning the idea. I will test the aluminium brazing rod on a bit of scrap first. Then see about trying it on this super small part.

I have been given orders to improve the state of the house in some fashion as we will be hosting a very small celebratory dinner tomorrow to recognise both offspring's successful graduation from higher education. It is happening as the all important cake was purchased today. :)
 
Joined
May 28, 2013
Messages
120
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Ottawa
So Danny, handle bar inner diameter is 18.3 mm outer diameter is 22.2 mm.

Re the handlebar plug imamedik, I dunno. That looks like I would be cutting open the end of the throttle body, which can be envisioned as a capped at one end where the tensioning bolt passes through to pull the spreader wedge towards it's head (the bolt's head)

The business end of the throttle is on the open end of the cylinder.

I will report that the Aluminum brazing stuff did not work well on this itty bitty part. In fact I ended up melting the cast bit. Despite trying hard not to. The brazing material kept flowing away despite surface prep. I will try it again on a better grade of aluminium later.

Steel! Suit up! You're on next!
 
Joined
May 28, 2013
Messages
120
Location
Ottawa
ok... pattern scribed in steel. Will cut it tomorrow. Still knackered from a 37 hour day, 15 of which was spent sitting in a hospital emergency ward with a family member. They need someone to AZ-ify those chairs!!!

 
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