Torque Arm Installation - Rear Hub - Best Practice?

[portals]

Having rejigged my rear hub setup and repositioned derailleur away from dropouts the rear hub axle now fits much snugger in end of dropouts. No more trips to local bike shop guy to get him to refit it

I have been messing with putting on two torque arms (one each side) and had a few basic questions, trying to get my head around what the best (strongest) way is to counter the opposite torque.

This it what my dropout looks like on drive side (pic below).

1. If I can fit the hammer ebike torque arm (pic below) in one of the two eyelets is this a STRONGER and so better solution that running the arm up the chain stay (or seat stay) and jubilee clamping it in place?

2. Do these eyelets tend to be a standard size of M5 (5mm), this is a decades old Halfords MTB.

3. Does it make any real difference what the order of the torque on the axle is, is it better to slide the smaller axle part next to frame when have other arm on outside or does this not really matter?

4. C-clips - what should they be used for, are they actually needed for any specific task or just another type of spacer washer?

5. Does the orientation of the two arms make any real difference, what I mean is in the two final pics you can see I've orientated the two arms (that make one arm) differently on the drive and non-drive side?

6. I would assume 'mixing' the configuration on both sides isn't a problem, so could mix hammer one side and standard arms other side etc. to get best fit as well as orientations as really it's all about not letting the axles fall out of the dropouts?

Any thoughts/tips appreciated.

Dropouts:



Hammer ebike torque arm - uses eyelets


Drive side - jubilee clip:


Non-drive side - jubilee clip, both parts of arm are orientated differently from drive side above:

 

[saneagle]

You can use the mudguard fixing point to screw directly into the main part of the torque arm, which will be much more secure. You need a 5% cobalt drill to drill the torque arm because the steel is pretty hard. You could drill right through with a 6mm drill and use a 6mm nut and set screw to hold it all together, or you can mark the torque arm through the hole and drill it say 5.5mm and use a 5mm screw through it into the mudguard fixing.

I don't trust those ones you show in the 2nd photo. The slot is too big for the rmm screw. I'd rather make my own arm with the holes in the right place out of a bit of strip mild steel. It only takes a couple of minutes.

Likewise, those ones with the jubilee clips around the frame are not very reliable. I've seen the clips break in their time of need, and they can also slip if you set it up so that the arm is going to move in the direction of the frame. It's a flawed design. It's better to forget the stupid jubileed clip. Just drill it and fix it to something solid with a screw.

 

[portals]

You can use the mudguard fixing point to screw directly into the main part of the torque arm, which will be much more secure.

By mudguard fixing point you mean one of the two eyelets in first pic, or something else?

Yes one short arm would be best, I will see how they all fit.

I don't trust those ones you show in the 2nd photo. The slot is too big for the rmm screw. I'd rather make my own arm with the holes in the right place out of a bit of strip mild steel. It only takes a couple of minutes.

Well I have one on way, keeping options open I suppose.

Likewise, those ones with the jubilee clips around the frame are not very reliable. I've seen the clips break in their time of need, and they can also slip if you set it up so that the arm is going to move in the direction of the frame. It's a flawed design. It's better to forget the stupid jubileed clip. Just drill it and fix it to something solid with a screw.

I was hoping maybe two of these and with the axle now being fully in dropout might be enough, maybe not.

 

[AntonyC]

Here's AlanB's TA done as saneagle prescribes:


and my Hammer arm done in the same sequence. You want an arm of the TA snug against whichever eyelet so as not to exert leverage on the 5mm threading.

 

[portals]

Thanks for replies.

So have made a custom TA that's looking a lot like a halloween ghost, I'll take it given time of year...




This is what it looks likes on the bike.

 

[portals]

Making progress...

 

[portals]

Looks like drive side will work too once I've removed the flange inside the derailleur dropout so it clears the screw.




Already removed the flange on the outside with my new favourite toy, an angle grinder!

 

[chris_n]

You may find that on the drive side the torque arm needs to be outboard of the derailleur mount to get all of the gears. Depends how thick your torque arm is and how much adjustment there is in the derailleur.

 

[AntonyC]

Nice, how did you transfer from printed template to steel accurately, especially the hole with the flats?

 

[portals]

You may find that on the drive side the torque arm needs to be outboard of the derailleur mount to get all of the gears. Depends how thick your torque arm is and how much adjustment there is in the derailleur.

Thanks, when I've got the steel version I will have a play to find the optimum order on the axle that still allows the H and L set screws to move across all of the cassette.

Tbh I don't use many rear gears, it's 7 speed and I tend to leave in either 3/4/5 use the front 3 gears to get some resistance when pedalling so I get some exercise.

 

[portals]

Nice, how did you transfer from printed template to steel accurately, especially the hole with the flats?

I'm looking at that now, either a local metal shop where I can give them the .obj / .stl / .svg and they can CNC cut it or use an online metal shop service to CNC it.

Or get them to trace around my template but that would be open to errors and last time I got something cut (2mm thick steel plate for 3D printer PEI sheet), they botched both the width and breadth by a good few mm....

 

[portals]

Final edit before it goes to CNC. Going for 4mm thickness, not sure 5mm would add anything.

 

[AntonyC]

Hang on, aside from the hole clearances that's a zero tolerance part. Are the holes slightly oversized as a simpler alternative to arc-ed slots? That would work but the torque limit for the 5mm frame threads will be low. Maybe it's wiser to follow the traditional 2 piece pattern with high torque on the external joint between the pieces?
(Sorry I was dozing up-thread )

 

[portals]

Yes holes are slightly oversized to allow fitting whilst still holding the axle firm, whilst I'm not the world's greatest 3D designer I have been doing this for few yrs now so am not a total numpty

General consensus here was the two 5mm eyelets is the way to go rather then the cheapo 2 arm TAs held with jubilee clips that I've posted above as that's a weak point.

I may just do both imagine that, 4 TAs on the rear hub...not see that before...

 

[portals]

Does anyone have any further comments on the pros/cons of using a one piece custom TA versus the cheap 2 arm TAs with jubilee clip?

 

[guerney]

Final edit before it goes to CNC. Going for 4mm thickness, not sure 5mm would add anything.

View attachment 60381

Is this for a 2000W motor? Although I know absolutely nothing about hub motors and their WTF PLC settings, I'm curious about what metal this CNC object is going to be cut from and how much it's going to cost. Suitability for intended use is for the experts to comment on, but could you thicken areas to add warp resistance?

 

[portals]

1500W motor (sheep, lamb etc.)

Current plan is TA will be cut using 4mm (or 5mm) 304 stainless steel, still looking at quotes, it's a small part, approx £20 - £30 for 2 pieces I will be ordering at some point next week.

Or I can buy my own 5mm sheet for under £5 and take that to local CNC guy, probably a better idea than online as all their 'online quote' systems are, being kind, ****...

 

[thelarkbox]

Does anyone have any further comments on the pros/cons of using a one piece custom TA versus the cheap 2 arm TAs with jubilee clip?

Cost??
Not an engineer, but it strikes me by the time the 2nd part of a 2 part arm comes into play the bike frame and or the first part will have already failed.

I would go with your design and SS or extra strong machine screws to fix.

 

[thelarkbox]

Also - a smear of jbweld between the matting faces might reduce the shear strain on the screws

 

[AntonyC]

By 2 piece pattern I was thinking of your CNC part but in 2 overlapping pieces, using the two 5mm eyelets and not a jubilee clip. Then precise orientation of the 3 holes and the flats is no longer critical, in fact the holes can be oversize, exhibit waterjet taper and what not. Just take out the slack by applying the opposite of in-service load to the 2 parts before torquing up.