Would you pay $80 for a torque arm?

[TricycleMichael]

Don't care much for the looks of torque arms and garden hose clamps that I see around. Grin and such.
I"m thinking about titanium. Costly to produce and what volume would be needed - thinking about 10k and $80 would yield a proper margin.
I know a bit about this. Please check out my YouTube post and search for "slickfoote" the video is titled "Stiletto Titanium Hammers."
Looks are important to me and this is my preferred style, can't find them anymore:

 

[scianiac]

I think the answer for most will be no when a Grin V7 is cheaper and better. The problem with torque arms and why they always look ugly is you have to make them to fit a very wide range of conditions. For instance that style probably won't fit as many bikes since you can't rotate the angle. And the fact that it's not clamping which one of the only ways you can really make a torque arm better. If someone really cares about looks the solution is often to just make a torque arm that fits the frame/fork perfectly. Also combined with the fact that the vast majority of hub motor builds are cheap builds, that is to say the Grin stuff is already way to pricey for the majority of the market. It's not a market that values premium products, it's a value market.

 

[wturber]

Ditto what @scianiac said. Take a look at the Torque Arm Picture Thread.

Here is my torque arm posted there. These rear dropouts posed a pretty difficult problem for many conventional torque arms. So I custom made my own.

torque arm picture thread

Only a Q100H, but it's an alloy frame, so I made two like this on both sides of the axle. Damn, after shaping the slots for the axle, I two ruined plates trying to drill the mounting holes. So I only used one hole. Decided to make the slot wider to accomodate the funny washers. Only a Q100H.

endless-sphere.com

BTW, I agree about the hose clamp thing. I really dislike it even though I can appreciate the utility and pragmatism.

 

[LewTwo]

Short answer NO !
Long Answer No: Easy enough to lay them out in a cad program and then have then laser cut or water cut from 1/4 inch SST.

 

[TricycleMichael]

"For instance that style probably won't fit as many bikes since you can't rotate the angle"

Mongo - The arms pictured are adjustable for angles differences and will fit over wires. Good point.

I like CAD and laser/water cut from SST. Just thinking about scale - 8 Billion people and possible manufacturing corp. buyout.

 

[neptronix]

I would buy a grin torquearm on the basis that it has dropout clamping. This has a greater effect of transferring torque than choosing a harder/better metal. This is because axle width in hubmotors are highly variable.

Grin is some decades into solving this particular problem & i know they have an excellent product. I'd be hesitant to try anyone else's unless it had clamping and angle adjustment also.

I think from a business standpoint you would have a hard time competing with them.
I suggest you put your efforts into doing something nobody else is doing well. That's where the good opportunities exist.

 

[Mongo]

Back to @scianiac's post, and his line, "It's not a market that values premium products, it's a value market."

I suspect the vast majority of hub motor conversions start by using the eBay/Amazon/Alibaba sub-$200 kits, by peeps that just want cheap transportation and/or fun - often they're not bicycle nutters, nor do they have to be. So, a $10 versus $80 torque arm they don't even know they should have (or why, until it's too late), and you can guess which purchase they'll click on.

 

[wturber]

"For instance that style probably won't fit as many bikes since you can't rotate the angle"

Mongo - The arms pictured are adjustable for angles differences and will fit over wires. Good point.

I like CAD and laser/water cut from SST. Just thinking about scale - 8 Billion people and possible manufacturing corp. buyout.

I see that you have it etched as patent pending. Unfortunately, I cannot read the patent number. I'm curious about what it is exactly that you are attempting to patent.

I can also see upon closer inspection that you have a rotatable spline for the flatted axle - seemingly similar to what Grin is doing. It wasn't obvious in the photo. So yes, it's adjustable as you subsequently pointed out.

The only other thing I'd add is what others have alluded to - I don't see titanium as being particularly necessary. Saving a few ounces (or less?) on and ebike component isn't usually particularly important. Not if it runs at a premium cost. The corrosion resistance would be the main strong point for titanium. But stainless steel manages that.

 

[99t4]

Judging by the majority of TA questions we get from posters requesting help with TAs or reporting problems, they are almost all using the cheap ubiquitous knockoff of Grin's long discontinued TA v1:

which is unsatisfactory on so many levels, but is ubiquitous, cheap, and seems to be almost universally offered in kits. Evidently most buyers don't know its pitfalls, at least until it fails.

So that is where the market is. Would need to make your TA cheap, efficient, easy to use, and (most importantly?) well-marketed.

 

[lnanek]

I use Grin's TAs. Sometimes I'm a little short on axle length, though. I suppose if titanium allowed the TA to be thinner for the same strength, there might be a benefit. Or if I only needed one TA instead of two, changing the tire becomes easier. It's so annoying, I forgot to put a bolt through my derailleur hanger last build, and still haven't bothered to undo everything to get that missing bolt in, ha.

 

[Mongo]

Hi @wturber - I think the torque arm shown in the first picture is something other than the OP's product idea - I think it's a NLA product from/of ampedbikes.com, and maybe something the OP has ideas of copying.

 

[wturber]

Hi @wturber - I think the torque arm shown in the first picture is something other than the OP's product idea - I think it's an NLA product from/of ampedbikes.com, and maybe something the OP has ideas of copying.

Ah OK. In that case he'll really want to understand that patent.

 

[neptronix]

I use Grin's TAs. Sometimes I'm a little short on axle length, though. I suppose if titanium allowed the TA to be thinner for the same strength, there might be a benefit. Or if I only needed one TA instead of two, changing the tire becomes easier. It's so annoying, I forgot to put a bolt through my derailleur hanger last build, and still haven't bothered to undo everything to get that missing bolt in, ha.

This is the one thing that makes me love the grin all axle and gmac.
One bolt to remove, then detach the quick release.

After owning one and having it make life so easy when chucking an ebike in a small car, i don't want a hub motor with regular TAs anymore.

I think the Grin G7 s more in the direction of secureness over convenience. But it is nice to know that a motor ain't goin' anywhere.

 

[TricycleMichael]

Mongo, I should have posted this photo:

 

[Mongo]

Thanks for the update @TricycleMichael - it helps a lot.

 

[Chalo]

I'll point out that like almost all uses of titanium in place of steel, this is an inferior material for the job. It's only 60% as stiff as steel, which matters in this application. And it's only as strong as fair-to-middling steel, so maybe less failure-prone than cheapo Chinese cheese-grade torque arms, but less effective than Grin's stainless steel TAs-- let alone some custom item made from 17-4 stainless, AR500 steel, or heat treated CrMo steel.

 

[Chalo]

which is unsatisfactory on so many levels, but is ubiquitous, cheap, and seems to be almost universally offered in kits.

If they're installed on both sides, rolled all the way forward before tightening down, and not used with regen braking, those are almost always enough.

The problems with them are either from reversing torque (regen), not sufficiently tightening the axle nuts, or anchoring them in a way that allows movement at the anchored end.

 

[LewTwo]

I see that you have it etched as patent pending. Unfortunately, I cannot read the patent number. I'm curious about what it is exactly that you are attempting to patent.

I can also see upon closer inspection that you have a rotatable spline for the flatted axle - seemingly similar to what Grin is doing. It wasn't obvious in the photo. So yes, it's adjustable as you subsequently pointed out.

Well our good friends in SEA have already copied the concept of the star shaped insert. However the emphasis should be on the word "copied" as they have 20 points on the insert. Grin has 25 points. An odd number of points allows the the insert to be flipped over and produce twice as many possible angular positions. When I first saw this 'star insert' design on Grin's web site, I searched all over to see if they had tried to patent it. I found nada.

 

[chuyskywalker]

Long Answer No: Easy enough to lay them out in a cad program and then have then laser cut or water cut from 1/4 inch SST.

Yeah -- Grin's options cover 99% of installs. For odd-ball installs, or for those have specific design desires, the readily available laser-cut-on-demand services cover them pretty well already. Heck, I needed to secure a grin AA torque arm in a weird spot which is a full 5 axis CNC made piece (not flat) and it was $113. The custom AA inserts I made (out of titanium for fun) were about $140.

 

[wturber]

Well our good friends in SEA have already copied the concept of the star shaped insert. However the emphasis should be on the word "copied" as they have 20 points on the insert. Grin has 25 points. An odd number of points allows the the insert to be flipped over and produce twice as many possible angular positions. When I first saw this 'star insert' design on Grin's web site, I searched all over to see if they had tried to patent it. I found nada.

Yeah. I did a search and Justin/Grin have only a couple patents that I could find. I think they are more concerned with innovating and moving DIY personal electric mobility forward than amassing intellectual property.

 

[TricycleMichael]

The answer is stainless steel, just wondering about ES peoples opinions.
Still for me a big high hand to Grin. They rule, so far.

One of my friends, also an experimenter DIY has been running the arm ahead of the fork. Looks funny to me - I'm really aware of
looks. His garden hose clamp is nicer visually than other I've seen:

.

 

[offGridDownUnder]

I don't see that titanium is a good choice for the part that contacts the axle flats - that is about resistance to deformation and ingress:

Tensile yield strength: 350 megapascals for steel; 140 megapascals for titanium.
Stiffness: 200 gigapascals for steel; 116 gigapascals for titanium.
Fracture strain: 15 percent for steel; 54 percent for titanium.
Hardness on the Brinell scale: 121 for steel; 70 for titanium.

Titanium Versus Steel: A Battle of Strength

In the case of my SX2, I use the Grin v7 clamping torque arm. Even that will ultimately be inadequate for that poorly conceived approach to torque resistance.

I would spend my money on a motor designed by people smart enough not to rely on axle flats. I recommend that the best approach to expanding the E-bike market is to stop giving money to stupid people - the 'extra' $$ I spend with Grin and some others (Solar 200 Watt Ebike Battery Charger - Sun200) pays off - I'm buying hard-won engineering expertise.

OTOH, "Good judgement comes with experience. Experience comes from bad judgement." So, it makes sense to try to DIY if my goal includes being willing to spend time and money learning - sometimes there ain't no other way.

I can see that the axle-flat approach permits a stepping stone approach of getting motors out there to build a market that will support a dedicated design.

I'm working up v3 of the motor mount cradle for my trike, and I can already see some of the changes I'll need to make for v4. I'll ride v3 for a while to be (more) certain I've caught all the shortcomings, but I hope v4 will be the long term version.

 

[docw009]

The window to patent the star inserts has passed. Prior art and all that. I bought a pair of torque arms with the star insert back in 2016 from a guy in Russia. They weren't as thick ...only reason I went to fabbing crude torque plates for my bikes.

I've also received the cheap grin knockoffs in one bike kit. As Chalo says, the small piece that fits around the axle does better if it can be screwed to the frame.

No, I wouldn't pay $80 for a torque arm because I don't do monster motors. Aside from the front drives, they're probably overkill on a rear drive 500w project,

 

[offGridDownUnder]

laser cut or water cut from 1/4 inch SST

Maybe.

My local cutter offers 0.2mm tolerance on laser, 0.3mm on water.

But. The cut surface is rough, and they say if I want to smooth it after, I should allow 0.5mm material removal to attain a uniform surface.

I'm thinking of the faces that contact the axle flats. A loose fit there will mean rocking under the drive-regen cycle. For that matter, the star contact faces are also a concern.

Maybe they're just cowboys.

 

[neptronix]

I would spend my money on a motor designed by people smart enough not to rely on axle flats. I recommend that the best approach to expanding the E-bike market is to stop giving money to stupid people - the 'extra' $$ I spend with Grin and some others (Solar 200 Watt Ebike Battery Charger - Sun200) pays off - I'm buying hard-won engineering expertise.

Dude, same here.

I like grin's stuff, they're the only ones pushing hub motors really forward at this point, otherwise it's mostly the same amazon/alibaba/ebay crap you already bought in 2012, but in a different package, blah.

Now OP knows who to beat, hehe.

ps - that solar charger is awesome!