Anyone have front hub accidents even with torque arms?

[alpharalpha]

Are front hub accidents common, even with torque arms and nuts tightened? Any motors lock up?
I've been uncomfortable using mine since I got it, only using 500w currently 27v but one day would like to use my full 36v of cells. Have 2 of these type torque arms
Replaced aluminum fork with a steel one--not hi-tensile unfortunately. Am seriously considering going with a rear hub motor but will have to buy another bike as this one is aluminum. I have mixed feelings, it doesn't feel dangerous, not a lot of torque and have c washers, torque arms properly installed and check the nuts pretty much everytime I go out. Just wondering what others experiences have been as I've heard about dropouts failing and motors locking up, have you or do you know of anyone to have these issues while using a front hub motor?

 

[spinningmagnets]

With two of those torque arms on a steel fork using roughly 750W....you should be fine. I would not hesitate to run that combination.

 

[amberwolf]

I"ve run thousands of miles on front hubmotors on CrazyBike2 and never had a wheel lockup, and with proper torque arms (wrenches in my case) never had an axle rotation issue (did have problems without them).


That said, *anything* can happen; even if you just had disc brakes on a normal wheel you could have a rotor or caliper failure that coudl cause a wheel lockup, or a stick in the spokes, etc. Or a water bottle come off the bottom of the downtube and jam in the tire/fork, which happened to Dogman a long time ago. Or a pothole that breaks enough spokes in the right way to disintegrate the wheel.

So there are no guarantees no matter how you do things.

It's just pretty unlikely if it's done right.

 

[anon0973923]

I don't have any worries about mine (single torque arm, 60Vx25A) but I upgraded my fork to a beast:

 

[alpharalpha]

The motor pull 30amps (864w) from a stop, though usually I pedal until up to 15amps (432w) and then at full speed which is about 18-22mph it tapers off to 10amps (288w.) I wanted to keep the force low on the dropouts and the top speed where it's at to minimize risk, and am pretty happy just not having to pedal all the time on those long runs, figured I'd ask on here since so many people run front hub motors.

 

[dogman dan]

You should not worry, unless you have a reason to.

If a nut keeps loosening for example, then something is wrong causing it. Regen can work a nut loose, but I'm thinking more about something else, that would result in a crooked washer. Like not having the c washers, or a too shallow dropout.

I did some 8000 miles of commuting, for 4 years, on front hubs. much of it with alloy forks. Set it up properly, and you are ok.

 

[alpharalpha]

Well here are some pics of the front fork setupView attachment 2View attachment 1

 

[John in CR]

With those types of torque arms on a front install, a critical part is orienting them properly. You want the axle twisting force to lever the torque arm so it pulls the axle deeper into the dropout. Incorrect installation can result in the opposite forces. Justin wrote something about how to do it properly...unfortunately I have no link as I've never used that kind of arm. Get it right and you'll be fine.

Also, increasing voltage doesn't increase the forces on the torque arm. That comes from torque, and increasing current is what increases forces on the torque arm.

 

[4sken]

Your build looks very solid imo, nice thick torque arms and low motor power. For my build I needed to get to and from work and had no other transportation available due to unforseen circumstances so I threw a 1000w front hub on an old (1980's) carbon steel road bike frame using a front wheel on the back and the hub on the front, and since I was planning on putting the hub on a frame with built in torque arms I didn't have any and used a 10mm fixed wrench and a hose clamp-single arm style. That build lasted over 100km without ANY pedaling (including some very irresponsible grassy bumpy joyrides, no regrets) until it finally started getting rotation issues from the forks disintegrating. I can tell you this now, though-If it fails, it will fail slowly and gracefully. Steel won't crack like aluminium so if the torque arms give you'll notice the wheel slowly shifting on the dropouts. You'll feel a mushy feeling and notice the bolts or axle rotating when torqued from a stop. You'll see stuff going wrong days before anything actually breaks. You're fifty shades of good here. I wouldn't worry about it

 

[alpharalpha]

Well I have the torque arms faced towards the rear, that's how I've always seen them done plus it would seem to me that with the torque going forward that the arms pulling against that would be best. Good to know that a failure would be gradual if ever.

 

[dogman dan]

I prefer to the rear, to have the arm pulling on the hose clamp. But if you have it actually bolted to the frame, I can't see what difference it would make.

Some would prefer to have the arm clamped to the fork in front, since then the arm will push on the fork. But since the fork is round, I'm not sure how reliable that would be.

Mo bettah, chuck the hose clamp, and fabricate a strong strap and bolt to secure the TA. Since this would only fit one bike once fabricated, it doesn't come with a TA.

 

[teklektik]

You want the axle twisting force to lever the torque arm so it pulls the axle deeper into the dropout.
Incorrect installation can result in the opposite forces.
Justin wrote something about how to do it properly...

Well I have the torque arms faced towards the rear,...

Exactly right.

The mounting side makes a huge difference.
If the applied forces aren't clear by inspection, then take it from Justin back in 2009 in his thread on Dropout Failure Experiments:

...The idea with the torque arm design was that second arm with the hose clamp goes behind on the rear of the fork, so that the axle torque is converted into a thrust that pushes the wheel further into the dropouts.

This is a pretty important point...
Some people installed with the torque arm facing forwards, and in this case the reaction torque on the axle would tend to pull the wheel out of the dropouts.

...with loose nuts it could be a problem. Say a powerful 80 N-m torque, and assuming a distance between the torque plate axle slot and pivoting point of 2.5cm, then that can translate into some 700 pounds prying the axle out or in to the dropout.

 

[melodious]

On top of all the good advice here, use a nordlock locknut washer in the same diameter as the axle. Set it and forget it, the nuts won't come loose, period. I bought 2 sets for each axle side two years ago and never had an issue with loosening nuts. I have horizontal dropout slots (Surly bike) and would occasionally get wheel alignment issues; the locknut washers also kept the rear wheel in place.

https://endless-sphere.com/forums/viewtopic.php?f=31&t=53470&p=795633&hilit=Nordlock#p795633

 

[alpharalpha]

I had to put a washer behind the torque arm to get it to line up with the fender hole, but then I read Grin Tech saying "spacer and washer to clear lawyer lips " so does a spacer/washer have to go behind the torque arm for it to line up? I thought this was something unique to mine and that it might affect it adversely having the torque arm further from the axle. Was considering getting one with the 2 hose clamps but do those also have to have a spacer/washer behind them to line up? I wouldn't think so as it doesn't have to line up with the fender hole, but I'm still new to this. I like the idea of those nord washers, would they go where the current washer behind the torque arm is at? I am thinking you mean for it to go behind the nut but there's not enough room with that washer there. Lemme try to get a decent pic
Unless the nord washer went where the spacer is at--or I can somehow get rid of that spacer (I'm halfway of the mind that the washer/spacer is meant to go on the inside of the fork/axle, but don't know)I don't have room for it.
And would those fender bolts benefit from being grade 8 steel or is that not an issue?

 

[USAEBIKECO]

Always use 2 torque arms, not just one

Avoid pot holes and other uneven surfaces that can knock the axle out of line.

 

[Chalo]

And would those fender bolts benefit from being grade 8 steel or is that not an issue?

Not an issue.

Grade 8 is an SAE rating that applies only to inch sized fasteners. The metric equivalent for your M5x0.8 fender screws is class 10.9.

 

[alpharalpha]

I picked up some of these following Dogman Dan's recommendation to strengthen my rear rack, so thought the same might apply here (btw, these were kinda difficult to find.) But you say no need?

M5 x 20mm - Qty 10 - DIN 912 SOCKET HEAD Cap Screws Black Oxide Grade 12.9

 

[Chalo]

I doesn't hurt to use high strength fasteners, but your installation isn't going to impose unusual forces on the screws unless they are left loose.

 

[alpharalpha]

I feel a bit better now from all the positive feedback, plus I emailed ebikes.ca and asked them since they sold it to me and from what I've read they're quite knowledgeable on this subject; Ben got back to me and said my setup looked good, that having washers like I do to make the torque arm parallel to where it mounts up is common and that even one torque arm would be enough for my output. Keeping my nuts tight are a pretty high priority, the torque arm either came with lock nuts where it goes thru the fender or I did it, either way they shouldn't loosen. Wish I had space for those nord washers just because I like things like that, probably from my sailing days, having things torqued tight, lashed down etc.

 

[ewinters]

Would it be too crazy to simply fabricate torque arms 100% with epoxy mass? Like a donut pressed on the axle around 1cm thick, which you could later drill and bolt.

Enviado de meu XT1580 usando Tapatalk

 

[amberwolf]

It's unlikely to be hard enough to withstand the torque. Either it will deform or shatter.

Even if you had it reinforced with a fiber of some type, the same results would probably happen.

But it'd be interesting to see a test, if you want to post the results of it up here.

 

[markz]

It wouldnt hurt to use Nord-Lock washers as well. Home Depot does not sell them, but any fastener store would.
I would use a steel front fork with 2 torque arms.

Also you can go to Home Depot and buy flat stock, I have seen them in the bolt aisle. I dont know how thick they come. Canadian Tire also sells flat stock. Princess Auto or HarborFreight would most certainly sell thicker flat stock. Then a grinder or jig saw with a new metal cut blade.

Or just epoxy thinner sheets together, and bolt them together.

 

[dogman dan]

No epoxy torque arms,, some have use epoxy to attach TA to the frame itself though.

The single most critical thing has been discussed in this thread, the importance of using spacer washers, or c washers, to get the alignment of the TA good, and or to get the TA to bear on the dropout cup, rather than sit crooked on the lawyer lips or edge of the cup.

FWIW,, I raced a bike with an estimated power of 4000 w, front hub, 110v. I used two torque arms, which bolted directly to the steel fork. I welded tabs to the fork for them to bolt to. In general,, the weak link on front torque arms is the hose clamp. But a hose clamp is quite adequate for normal power bikes. Use two TA if your fork is an alloy shock fork. One is plenty for most steel forks, with 48v motor or less.

As you install a TA, the axle will try to spin towards the front, as the wheel spins to the back. Snug it up by rotating any slack in the TA to the rear.

 

[motomech]

Well here are some pics of the front fork setupView attachment 3View attachment 2View attachment 1

You should get the correct size wrench and use the closed end when possible so you don't chew up the nut anymore.
I use lot's of blue Loctite and don't clean the threads when the nut is removed. After two or three applications, the nut will not loosen.

 

[alpharalpha]

Well here are some pics of the front fork setupView attachment 3View attachment 2View attachment 1

You should get the correct size wrench and use the closed end when possible so you don't chew up the nut anymore.
I use lot's of blue Loctite and don't clean the threads when the nut is removed. After two or three applications, the nut will not loosen.

I've got a wrench set now, that was done when I first got the wheel, I'll get some of that blue loctite.