Is one torque arm enough?

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Re: Is one torque arm enough?

Postby John in CR » Tue Apr 24, 2012 7:46 pm

Is anyone actually surprised that this has started happening?
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Re: Is one torque arm enough?

Postby auraslip » Tue Apr 24, 2012 8:49 pm

Not really. The instructions weren't really clear in the thread. Maybe an install guide would be nice.

But just to be clear - you roughed up the drop out with a file. Did you also rough up the torque arm as well? Mind were covered with some sort of corrosion or something. Did you use a solvent? Did you apply pressure as it was curing?

I haven't done the math, but 4200 psi is an awful lot of shear strength. If they're installed good, they should hold. But I haven't done the math. Has anyone?
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Re: Is one torque arm enough?

Postby keysersoze310 » Wed Apr 25, 2012 10:17 am

auraslip wrote: But just to be clear - you roughed up the drop out with a file

Yes
auraslip wrote: Did you also rough up the torque arm as well?

Yes
auraslip wrote: Mind were covered with some sort of corrosion or something.

Mine were too, spent quite a while using my metal file to get rid of all the corrosion on the side I epoxied
auraslip wrote: Did you use a solvent?

Just cleaned it with alchohol
auraslip wrote: Did you apply pressure as it was curing?

Yep, clamped it down hard
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Re: Is one torque arm enough?

Postby izeman » Wed Apr 25, 2012 10:35 am

another thought: maybe you bought a 'fake' product? nowadays there are piracy products everywhere. could have happened here as well. even pros can't tell the good from the bad stuff.
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Re: Is one torque arm enough?

Postby auraslip » Wed Apr 25, 2012 11:54 am

Well this sucks. Now that I'll need to to drill through it, this drop out has ended up costing me twice as much as making my own.
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Re: Is one torque arm enough?

Postby psycholist » Wed Apr 25, 2012 5:25 pm

keysersoze310, You had a problem with a very loose fitting axle, resulting in a lot of rocking play in the torque arm and loosening of the axle nuts.
Did you ever resolve this issue? If you continued to ride in this state, something is bound to fail.
The integrity of the doctorbass torque arms require that the axle nuts be tight as well as a snug fit in the (torque arm) dropouts.
What might have occured here, is that you continued to ride with this condition and the loose axle nuts, accompanied by the constant rocking, caused the system to fail at it's weakest link...The epoxy bond.

I'm not implying that you did this. Just a possible scenario :)
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Re: Is one torque arm enough?

Postby auraslip » Wed Apr 25, 2012 5:44 pm

:(
Image
i'd like to think john for making me paranoid. LOL.
What happened was me drilling out the anti-crack hole. I guess it got warm and weakened and the torque from the drill popped it off. You can debate this all you want. I don't think I got it too hot.

Image
Here is the solution I'm working on. Huge pain ;(
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Re: Is one torque arm enough?

Postby auraslip » Wed Apr 25, 2012 5:45 pm

Think I may have found our problem -> http://www.alibaba.com/trade/search?Cou ... cotch+weld

I got mine off ebay.

I've contacted the seller as well as 3m.
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Re: Is one torque arm enough?

Postby keysersoze310 » Wed Apr 25, 2012 6:33 pm

psycholist wrote:keysersoze310, You had a problem with a very loose fitting axle, resulting in a lot of rocking play in the torque arm and loosening of the axle nuts.
Did you ever resolve this issue? If you continued to ride in this state, something is bound to fail.
The integrity of the doctorbass torque arms require that the axle nuts be tight as well as a snug fit in the (torque arm) dropouts.
What might have occured here, is that you continued to ride with this condition and the loose axle nuts, accompanied by the constant rocking, caused the system to fail at it's weakest link...The epoxy bond.

I'm not implying that you did this. Just a possible scenario :)


You are correct I had a rocking issue, but that was due to regen. My solution was... just don't use regen. I've only tested it out on low regen a couple of times like in the video I posted, so that wouldn't be nearly enough to cause this problem. The axle nuts were always kept very tight with nord lock washers.

@aura
Bummer. First off, I think you might have used the wrong epoxy? Its the black DP-420 that has the highest strength I believe, though the off white is probably strong enough as well.

I bought my epoxy on ebay as well... I think you might be on to something here. For the record, I'd stay away from ebay seller 9835tanzy just to be safe.
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Re: Is one torque arm enough?

Postby izeman » Thu Apr 26, 2012 2:35 am

auraslip wrote:.. I guess it got warm and weakened and the torque from the drill popped it off. You can debate this all you want. I don't think I got it too hot.

drilling a hole with a not 100% good drill can make the plate very hot. and heat is the only way to remove epoxy. and once it got hot it's like dried jewing gum. can you pry the remaining epoxy off with a screw driver easily? if it falls of in small crumbles than you know it got too hot.
this must not be mixed up with applying heat while drying of the epoxy. there are some types that need heat to become harder. other type will stay like glue one heat is applied and will never dry.
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Re: Is one torque arm enough?

Postby psycholist » Thu Apr 26, 2012 3:48 am

Glad to hear you resolved the rocking issue keysersoze.
Seems like you did a thorough prep job. Gotta be the poor quality epoxy.
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Re: Is one torque arm enough?

Postby John in CR » Thu Apr 26, 2012 10:01 am

psycholist wrote: Gotta be the poor quality epoxy.


OR ___________ . I'll leave it up to people to fill in the obvious answer on their own.
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Re: Is one torque arm enough?

Postby neptronix » Thu Apr 26, 2012 10:59 am

Image

Image

These are still working at 7kW, 1.5 years later.

I don't believe in this glue stuff.. just does not calculate. bolt or weld it on..
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Pro-tips for noobs: Charge RC Lipos to 4.15v, stop discharging at 3.5-3.6v | Use torque plates/arms! | Rear mounted hubs are always best
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Re: Is one torque arm enough?

Postby ZOMGVTEK » Thu Apr 26, 2012 11:23 am

I was planning on clamping the dropout with a single bolt in an open area, and then welding the perminter. If I can't trust the dropouts with the task of holding the wheel, why bother? I ended up going another route and the doc torque plates were not required.

Adhesives work, and can be very strong. However, they are EXTREMELY sensitive to the materials being bonded, and prep involved. You can't glob some smoo on sanded paint and think its going to hold back 20HP. I was a bit worried when I initially noticed rather inexperienced people trying out DP420 for really critical stuff, looks like there was good reason.

At the end of the day, most stock dropouts are stronger than people assume. Good steel dropouts will take at least 6kW no problems. Toss in regen, and the axle will start to rock, trashing the dropouts and loosening bolts. My stock dropouts are happy at 8kW, but 1,600W of regen makes the EXTREMELY tight axle nuts rock, even with nordlocks. A solid torque arm/plate solution is a great idea, but not ABSOLUTELY required for most low power builds. It just depends on the speed involved, and how much of an issue loosing your wheel is to you.
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Re: Is one torque arm enough?

Postby neptronix » Thu Apr 26, 2012 11:33 am

yeah, some steel bikes are great.. but not everyone's down with steel ya know :)

What we really need are 16mm or wider axles. That makes the torque forces spread out around a larger area, which is far more forgiving to a poor torque arm/plate configuration. Then you don't have to get the axle part as perfect.

Because the docbass torque arms i bought are so loose, they are basically $35 worth of scrap metal to me. I don't see how they'd work as clampers, especially when you're gluing something on, then stressing out the bond that glue ( ok, epoxy ) has made.
ES facebook group: https://www.facebook.com/groups/125035107565566

The all-arounder: 8T MAC motor on a Trek 4500.
The girlfriend bike: 350W front MAC on a 700c Trek.
The wheelie machine: 20" Rear Magic Pie II on a Trek 4300 MTB
The Bus: ??? on a 'da bomb' cargo bike frame

Pro-tips for noobs: Charge RC Lipos to 4.15v, stop discharging at 3.5-3.6v | Use torque plates/arms! | Rear mounted hubs are always best
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Re: Is one torque arm enough?

Postby ZOMGVTEK » Thu Apr 26, 2012 11:49 am

neptronix wrote:Because the docbass torque arms i bought are so loose, they are basically $35 worth of scrap metal to me. I don't see how they'd work as clampers, especially when you're gluing something on, then stressing out the bond that glue ( ok, epoxy ) has made.


Did you measure the ID on them? IIRC Doc measured his 5405 at something like 9.8mm, which is a bit off from the more typical near 10mm width the torque plates were intended for.
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Re: Is one torque arm enough?

Postby neptronix » Thu Apr 26, 2012 12:18 pm

My digital caliper is outta battery.. but they are loose enough to rock around a bit on the MAC motor.. bit more snug on the golden motor, but still loose. That's all i know.

When i had the torque plates made, i made them a tad too narrow so that you could file them by hand to get 'em super super tight.

These are probably made to be tight for a crystalyte..
ES facebook group: https://www.facebook.com/groups/125035107565566

The all-arounder: 8T MAC motor on a Trek 4500.
The girlfriend bike: 350W front MAC on a 700c Trek.
The wheelie machine: 20" Rear Magic Pie II on a Trek 4300 MTB
The Bus: ??? on a 'da bomb' cargo bike frame

Pro-tips for noobs: Charge RC Lipos to 4.15v, stop discharging at 3.5-3.6v | Use torque plates/arms! | Rear mounted hubs are always best
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Re: Is one torque arm enough?

Postby psycholist » Thu Apr 26, 2012 1:11 pm

John in CR wrote:
psycholist wrote: Gotta be the poor quality epoxy.


OR ___________ . I'll leave it up to people to fill in the obvious answer on their own.


neptronix wrote:I don't believe in this glue stuff.. just does not calculate. bolt or weld it on..


Well, Being a certified welder, you can imagine what my biased opinion would be regarding this "glue". I had my doubts just like you guys. A company I worked for was testing this glue-bonding method with aluminum. I was truly shocked when I examined the results of the stress test. The aluminum tore at the parent metal adjacent to the bond, while the actual bonded section remained intact! This was ~12 years ago and I would assume the stuff available today is probably even better.

I do agree though, If you can bolt it or weld it, do it. ... dumb welder revealing his biases again.
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Re: Is one torque arm enough?

Postby izeman » Thu Apr 26, 2012 1:31 pm

i think epoxy is a really great thing. if used properly and if you got the right stuff.
there must be a reason why today many parts in cars are glued and not bolted or welded. glueing is superior to welding/bolting to some degrees and to some it's vice versa. it*s as simple as this.
bmc trailfox, mac12t, 12s lipo: viewtopic.php?f=6&t=32267
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Re: Is one torque arm enough?

Postby psycholist » Thu Apr 26, 2012 1:57 pm

izeman wrote:i think epoxy is a really great thing. if used properly and if you got the right stuff.
there must be a reason why today many parts in cars are glued and not bolted or welded. glueing is superior to welding/bolting to some degrees and to some it's vice versa. it*s as simple as this.

I totally agree with you. I believe the epoxy method could work in a torque arm application, providing the axle nuts are tight and the cutouts for the dropouts are snug. But I can also forsee problems when using regen or when there is excessive force applied to the torque plate in the same axial plane as the bond.
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Re: Is one torque arm enough?

Postby auraslip » Thu Apr 26, 2012 6:16 pm

drilling a hole with a not 100% good drill can make the plate very hot. and heat is the only way to remove epoxy. and once it got hot it's like dried jewing gum. can you pry the remaining epoxy off with a screw driver easily? if it falls of in small crumbles than you know it got too hot.


I think this was a large part of the problem. The plate got very hot. Hot enough to touch for a second, but still obviously hot enough to make the stuff fail. I didn't even think of heat being a problem even after reading completely through the long printed manual that came with the dp420.
Yes, the rest of the epoxy was easy to peel off.
I'm not going to lie, I didn't take machine shop in school, and it was totally my fault for letting drill run too fast. Up until yesterday I didn't know what feeds and speeds meant. Ironically, I was bitching about how hard docs torque arms were, but my frame is made of some type of air hardened tool steel and was actually harder to drill through than the TAs.

However, they are EXTREMELY sensitive to the materials being bonded, and prep involved. You can't glob some smoo on sanded paint and think its going to hold back 20HP. I was a bit worried when I initially noticed rather inexperienced people trying out DP420 for really critical stuff, looks like there was good reason.


Yup! Just the fact that the applicator gun is $75 should tell that this is stuff isn't for newbs. It might actually be cheaper to have someone weld these on. It would definitely be cheaper to buy the drill bits and taps to screw these in.

Because%20the%20docbass%20torque%20arms%20i%20bought%20are%20so%20loose,%20they%20are%20basically%20$35%20worth%20of%20scrap%20metal%20to%20me.


This may not be his fault. They may fit fine on some axles, but not on others. In any case, it should be up to the end user to file them down so they're tight enough for you to have to tap the axle into them with a mallet. He needs to leave a bit of extra space!

Image
Here is what mine finished up to be. Clearances were tight, especially on the side you can't see.
I was worried that the top bolt would prevent it from clamping, but you actually don't need very much of a cut to make them clamp on the axle.
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Re: Is one torque arm enough?

Postby John in CR » Fri Apr 27, 2012 4:38 am

Auraslip,

The drill bit was probably dead by the time you got to the bike piece. The expensive drill bits require low rpm and frequent cooling, even dipping in water a number of times for each hole extends the life tremendously. Get it hot with too much rpm and you can kill it in seconds. Typically a squeaking sound while drilling tells you the bad news.

I love epoxies and use them whenever I can, but there's just no way torque arms is an appropriate application. I did come up with one good thing to say about it. With good prep and using one on each side it's pretty unlikely that both are going to give at the same time.

The demonstration Doc did was like a 3M salesman's demo or those done to show how strong Superglue is, and I'm sure we've all seen superglue bonding failures. A more realistic test would be to bond a steel bar to aluminum, do a bunch of warming and cooling cycles, hang some weight on the bar, and then start banging on the joint with a big hammer hundreds of times to simulate each month of use. That's a lot closer to simulating what really goes on with a torque arm, especially with regen which is absolute torture with thousands of pounds of force at a 5mm radius alternating direction. Failure is all but certain.

Even simply considering the fact that a significant percentage of people will use a lesser epoxy and/or not adequately prep or cure. Almost no one appreciates the forces inside a dropout with a hubmotor until they've had a failure, and even then most don't appreciate the real risk. Spinning the axle and having to replace the motor harness is a real pain in the ass, but the real risk is if the spinning motion causes the the axle to climb right out of the dropout and suddenly the wheel is off the bike.

I got really lucky with my failure which was in the first 10ft of my first hubmotor ride. It was a front motor with a 72V20A controller. I fabbed 2 stainless steel torque arms with rectangular holes that fit the axle flats quite well. At the time I figured the 1/8th stainless on each side giving me .25" total was plenty strong. I was right that the stainless was strong enough, because it didn't deform at all. The axle torque just made it cut through the axle like butter, snapping the AL dropouts like butter. I only got lucky and avoided an asphalt face plant because it was only a couple of mph and the hose clamps securing the torque arms were able to hold the spinning axle in the slight indentation that remained at the top of the dropout.

I've used nothing less than 1/2" of steel with a tap in fit on each side since then, and regen deforms that fairly quickly. Clamping dropouts is the only solution, and I use it on every build. With Hubmonster I used 3/8" leaf spring steel to make these 20mm wide dropouts for each side. Even clamped firmly with 3/8" #8 bolts after less than 2 weeks with regen I heard the familiar clicking of rocking dropouts. It had all but disintegrated the lock washer, so now it's a hardened steel flat washer and red Loctite. If it happens again then I'll have to spring for the Norlocks.
Super V dropout for Hubmonster.JPG
Super V dropout for Hubmonster.JPG (18.56 KiB) Viewed 571 times


If I get looseness with this with 14mm dropouts on a 1" axle and an extra strong clamping bolt holding over a 3/4" width of axle on each side, imagine what a joke glued on 3/8" pacman torque arms that loosely fit less than 10mm flats are. :mrgreen:
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Re: Is one torque arm enough?

Postby auraslip » Fri Apr 27, 2012 12:14 pm

The drill bit was probably dead by the time you got to the bike piece. The expensive drill bits require low rpm and frequent cooling, even dipping in water a number of times for each hole extends the life tremendously. Get it hot with too much rpm and you can kill it in seconds. Typically a squeaking sound while drilling tells you the bad news.


I know that now.... :lol: oh well.

I wonder if we haven't seen more failures of the epoxy because for most people, properly tightened nuts are strong enough?
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Re: Is one torque arm enough?

Postby Ykick » Fri Apr 27, 2012 12:24 pm

Bicycle power levels and no regen the pinch of properly torqued axle nuts does seem to be enough IMO. John's got the ideal design for high power setups though! That looks perfect while reasonably simple to execute!

I've burned enough drill bits to learn a simple rule - the harder the material, the slower RPM for the bit. Oil/water, glycol, ATF - use something to help cool the work.
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Re: Is one torque arm enough?

Postby waynebergman » Fri May 04, 2012 10:24 pm

My take on this is that if you have the epoxy between the flats of the torque arms and the original drop outs and this is your primary bond you may damage the epoxy by tightening the axle nuts. The compression put in place but tightening the nuts after the epoxy has set may be too great for the epoxy to take.

Doc's treatment if I remember right had a totally different method with a cut out of the original drop outs larger in diameter than the TA's so you are using the sheer strength of the epoxy with out crushing the epoxy with the force of the tightened axle nuts. Just my opinion here but I don't see anyone pointing this out yet.
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