A comment on the Grin v7 torque arm assembly

[offGridDownUnder]

As pointed out yesterday by the fabricator I am working with (Quantum Bicycles in Perth - I don't have a shop and they really know what they are doing).

With the Grin v7, there are two pinch bolts to provide serious compression on the axle clamp. The comment is to tighten them progressively - a bit of one, then the other, alternating. Tightening one first before the other can tilt the clamping pad causing it to jam in the channel well before it's tightened enough to provide enough clamping force. He even suggested working up to the full 12 N-m final bolt torque to avoid this - 2 - 4 - 6 etc. to avoid jamming.

 

[amberwolf]

Since the manual

https://ebikes.ca/amfile/file/download/file/260/product/1670/

doesn't specify how to tighten this, I'd recommend dropping a note to Grin info@ebikes.ca so they can add that for future revisions.

 

[neptronix]

Ah yeah.. not unlike torqueing down a valve cover gasket.

 

[amberwolf]

Which most people have no idea how to do. (and don't normaly need to...making it better to have this kind of detailed instruction in any manual for a device that needs this done).

I've fixed plenty of broken things of all kinds where it was obvious the mounting screws around it were tightened down completely one at a time, instead of a bit at a time on opposing sides or even just sequentially. Even brand new from factories.

 

[DogDipstick]

I anticipate this problem and designed around it.

Anybody working on their own bikes, or for someone else.. should be able to figure this out. Dont strip the bolt. ok. Dont force things. ok. Use more thread. Maybe use a real tq wrench some day too.

Yup.

I have seen many offerings of tq. arms and the GrinV7 is certainly the best retail. 100% the best. Nothing close to it . Its good metal.

Grins is kinda similar but mine is much strongers. I could tell you how the forces work. I think. Where the flaw is. I have my mooring sothat I can adjust the bearing force... like an old steam engine Babbit... and some screws locked against themselves... ( threads and surface area engagement increase.. like a 4 bolt main, not a 2 bolt main... Close fits. Low tolerance. Some lockwire and locktite to boot. )...

Plus I know some gunsmithing. Lol. Lil machining and tooling. DIY There is alot to know.

These have supported this 31lb motor, 41lb wheel,.... bike,... for about two years now at 60mph on the gusseted 14lb frame. Zero looseness or wear on the dropout or the axle.


Poem time.
Crimp' crepe' cramp' Krumpped. twist and turn... All you yearn .. pre-stress the tensile..... but... dont yield.... to your ... urn ...Just go another while. Its your fault if you F**K up your own bike and dont smile.

 

[99t4]

Very impressive DD. What is the purpose of the thread spools?

 

[TuomasK]

V7s work great. Using one each side to support 200Nm peak torque.

 

[DogDipstick]

Very impressive DD. What is the purpose of the thread spools?

Protect the axle nut in a crash, also a place to put the jack stands to have the bike sit there and work on it. Like they do at the racetrack with one of these stands. Its called a " Track Stand" and you wheel it up to the rear of the bike, set the bobbins in the little holders, and lever the rear of the bike into the air.

A track stand.