Spun front axle and flew over the bars @ 25mph

[Kurt]

After reading this post I am surprised I didn't get hurt that bad in a bike accident I had when I was a teenager.

I was riding a light weight road bike from my house down a steep hill to my friends place about 3km away. It was summer and I had just shorts and a t shirt and thongs.I was carrying a steel air foot pump that my friend wanted to borrow.I had the hose warped around my wrist so I could still use both hands and lean down over the handle bars.I was really pushing the bike hard in top gear.I would say around 60kmh towards the bottom of the hill .

Next thing I know there was big noise and I was flying through the air a long distance. Then a big impact on my feet then head then back then feet again kinda like multiple cart wheels. When came to a rest I had some cuts on my back and a sore ankle and a bump on my head. I was a little freaked out and upset my new bike was damaged but i was prob in a bit of shock to. My friends perants took my to hospital but I checked out ok.I was a bit sore for a few days with a little bit of grazing on my back and a sprained ancle.

When I looked at the bike that had the pump dropped into the front wheel I was shocked. About 1/3 of the spokes were snapped the wheel was sitting up Almost level with the top tube of the frame and the forks were bent about 90 deg. The pump remained jammed in the wheel and was close to being cut in two.

It took me a while to get that thought out of my head when riding again. I us to check my quick relies front wheel about 1000 times before riding.

Type in (snapped front forks) into Utube there are some nasty videos on there. Usually aluminium frames.

Kurt.

 

[Drunkskunk]

If I may misquote Kenny Rogers,
"You picked a fine time to leave me lose wheel."


Glad you made it out alive.

 

[methods]

You broke the golden rule....never buy a bike a wal-mart.

Man if that is not the truth. . .

To be fair, I did not walk into Walmart and buy it. I bought the bike at a Garage sale thinking that someone had built in only to find later (searching Google for parts) that it was originally sold at Walmart.

Yep.

I think I deserves some sort of dumb-ass award.
Not for making these mistakes, but for letting my wife ride the bike
I dont really care if I get hurt but it would really suck if it had been her.

-methods

 

[Toshi]

This shouldn't be considered an indictment of front hub motors but rather of shoddy Walmart engineering and, most importantly, a lack of torque arms. After suffering a high speed failure of my own crescent wrench torque arm (yes, singular), thankfully without an over-the-bars incident, I went and had them done properly:

(Everything is free from rust and painted in rustoleum now.)

 

[methods]

Now those are some proper torque arms

Seems clear that the forks are going to fold long before those give loose.

-methods

 

[dogman dan]

Nice! I particularly like the mount to the fork, no cheezy little strap. This case was an exception, but I think 90% of spun axles begin with a washer deforming, which creates the loose nut. What we need is front or rear forks designed to handle the force of the motor. What I have in mind is a big flat dropout a centimeter thick or more, of hardened steel like a wrench. This would look a lot like the above torque arms, and actually bolt onto the fork to allow removal of the wheel. Literaly would allmost make the nut redundant. Of course, this dropout would bolt onto a nice suspension fork, or rear swing arm.

Don't blame wallyworld that we bolt insane stuff to our bikes! As for them being crap that don't last, my cheapo bike now has 1800 miles on it. The tires wore out quick, but the rest is fine, IF you tune it regularly. On second thought, I did wear out a crank and chainwheel set, but the upgrade to top quality cost 10 bucks from a garage sale bike. Stock saddle was of course, history in 5 minuites. But the rear rim, shifters, brakes, etc are all good as new, once tuned up.

 

[BikeFanatic]

I guess I can't wait on those torque arms, Glad you are alright.

I removed my rear wheel to fix a flat and next trip when I took off the rear motor spun out right away. I had only moved a few feet.

So I am thinking of getting some new bolts/nuts so I can double bolt to prevent loose nuts, and I have been looking at torque arms, these Torque arms ones seem pricey to me, as I would use two, but IF It saves my ass, it is worth it. Not sure if they would work with C lyte as they may interfere with the wires as they come off the axle.

http://www.hi-powercycles.com/product.sc?categoryId=7&productId=13

Anyone know what size threads the C Lyte 400 series Nuts are?

 

[dnmun]

i think they are 12mm 1.25mm thread, maybe you can use lugnuts from an import car. have neighbor or friend who works on cars? that would be a source. BOL,dm

 

[vanilla ice]

I'm using one of those 12x1.25 lug nuts on the left side of my hub inside the drop. Even has a built in 60 degree concial bevel for wire clearance.

 

[methods]

I use 14 x 1.5 automotive lugs on the rear of my bike.
Double the thread contact

 

[Toorbough ULL-Zeveigh]

Now those are some proper torque arms.
-methods

totally.
I think they're the best ones I've seen on here to date.
I'm no metallurgist, but my gut feeling is that tool steel is to brittle & you want a softer steel that will stretch b4 it snaps.

@drunkskunk
whenever something fails on my bike the lyric that always springs to mind;
'yooooooo left me,
just when I needed you most.'

 

[AussieJester]

Yeah they are nice torque arms and all aren't they methods but mate,
you still really think they are necessary i mean common, its alot of effort isn't it mate...i would spend the time making a permanent camera mount on your bike and just "wing it" and hope the motor holds without the torque arms LOL


Take not of themz torque arms and implement Method LoL

Nice work Toshi

 

[methods]

That is fine advice.

-methods.

 

[skydog]

I don't know if I'll be doing front hub motors any time soon but if I was I think I would use:
Forks with no "Dropouts" (slots to drop in and out) but just a hole in which the axle must be drawn through. I don't know if this would work on all motors but when possible, increases the forks surface area in a critical location.
Use a wirenut arrangement similar to aircraft.
At the very least use those cheapo lockwashers that have the tabs that bend up to the flats of the nut.
And of torque braces of some sort. (I really like the ones on the old cruisers from the 50s that had a slim rod that went from from top to bottom and arched outward. Very elegant but maybe not the toughest.)

BTW: Method, I think the motor going into regen mode would've thrown you over the bars whether the fork failed or not. Not that there is any consolation in this but there is a culprit prior to the fork failure that would have rendered the same results regardless of how the fork was braced.

God watches over drunks and E-Bikers

 

[Doctorbass]

Hey Methods, glad to hear you are still alive!! .. I mean.. falling at 25mph ... OUCH

You know my oppinion about regen... :? ... and dropout...

But i wonder what is your regen current setting??

Usually regen will does the same power than a producing a hard acceleration on high current mooded controller.. and i know that reversing torque direction on the axel can be fatal... for the drop out.. and for you...

Now, please Methods.. try to avoid Murphy's law!!! we dont want you to have a third accident!!

:wink:

Doc

 

[methods]

I have done away with regen on my "real" ebike.

Since I disabled regen my motor temps have been much lower. I dont have definitive numbers but with regen the motor got so hot that I could smell it on hard rides. Now it only gets hot enough to burn my hand

-methods

 

[Reid Welch]

Gee, that's nasty and a very good warning as well.

The "prevention" of that scenario for me is my choice of the freewheeling eZee geared motor.
No regen possible, no spin-out like yours possible, as you know.
Knoxie's BMC (sp?) type is the same thing at basis.

Well, I'd still feel better having a torque arm, freewheeling front hub motor, or not.
But at my 36V...it seems unlikely to need a torque arm. In forged steel dropouts we must trust...

Wow, man, were you lucky. Could have been....Goodbyesville.

GLAD you are OK, for sure. We need E.S. members, not dismembers.

 

[AussieJester]

we dont want you to have a third accident!!

lets not go overboard now Doc LoL... Long as he doesn't get injured OR break his bike and most importantly getz it all on film we are of the opinion that he is fine to take the odd spill for our comical enjoyment LoL...

Poor 'ol Methods, he be all padded up like the Michelin man before long

 

[docnjoj]

Hey Reid! I have spun several geared frewheel motors!. It just take overvoltage and some stupidity! You are right you cant do it on overrun! Torque arms are a must with geared motors! The torque multiplication is for real!
otherDoc

 

[ZapPat]

Methods - Like Doc I wonder what your regen seting was, and what controller you are using?

It seems to me that the real problem is the *implementation* of the regen, because the controller should not permit doing regen up to such a high current, and specially so abruptly. I mean a controller that permits you to go from no regen to maximum in under a couple seconds is just not smart! I am taking note of this type of unwanted behavior to avoid in my own controller, you can bet on this!

I also wonder how efficient the regen on current ebike controllers is, since the motor seems to be heating up a lot. This would indicate very bad power factor control being done by the controller during the voltage step-up needed for regen. Implementing better current control during regen would no doubt make the motor run cooler, and is also very necessary for safety, as we can see from this type of accident.

Any opinions an this subject?

 

[Doctorbass]

Hey... wait a minute...!..

Are we talking about regen THAT RETURN THE POWER TO THE BATTERY OR REGEN THAT SHORT THE MOTOR TO DISSIPATE THE ENERGY INTO IT IN HEAT ???

Cause if the Methods's motor heat so much, i would guess that it's because of the controller would just short every phases instead of conducting to put back the energy into the cells? right?

Doc

 

[methods]

This was not even a regen controller.
I was using a standard peddle first 20A 36V controller
These controllers will "regenerate" when the motor voltage exceeds the battery voltage
I was running 12S Lipo batteries that were discharged down to about 40V
The peak regen current was 14.7A (peak occurred at the time of the incident)

The 20" wheel was turning at 25mph which (apparently) was fast enough to push 14.7A back into a 40V Lipo battery

Nobody is saying that the regen braking was particularly strong. . . It only takes a little when you consider all the factors.

Walmart forks + no torque arm + strong forward speed + abrupt axle breaking = increased probability of a spun axle.

-methods

 

[methods]

Hey... wait a minute...!..

Are we talking about regen THAT RETURN THE POWER TO THE BATTERY OR REGEN THAT SHORT THE MOTOR TO DISSIPATE THE ENERGY INTO IT IN HEAT ???

Cause if the Methods's motor heat so much, i would guess that it's because of the controller would just short every phases instead of conducting to put back the energy into the cells? right?

Doc

Regen implies back to the battery in my mind.
Otherwise I would call it a crow-bar brake

Regen currents on the motor that gets hot (mind you this is a different setup that what we are talking about here) are around 20A @ 100V so 2KW regen. No motor can regenerate 2KW without creating heat regardless of how efficient the firmware is.

-methods

 

[Tiberius]

This was not even a regen controller.
I was using a standard peddle first 20A 36V controller
These controllers will "regenerate" when the motor voltage exceeds the battery voltage
I was running 12S Lipo batteries that were discharged down to about 40V
The peak regen current was 14.7A (peak occurred at the time of the incident)

The 20" wheel was turning at 25mph which (apparently) was fast enough to push 14.7A back into a 40V Lipo battery

Nobody is saying that the regen braking was particularly strong. . . It only takes a little when you consider all the factors.

Walmart forks + no torque arm + strong forward speed + abrupt axle breaking = increased probability of a spun axle.

-methods

Hi Methods,

Not sure this can be right. With a "standard" controller you can only put current into the battery if the wheel is turning faster than the battery could turn it. You can't go straight from forward thrust to regen.

Glad you're still with us, though.

Nick

 

[ZapPat]

This was not even a regen controller.
I was using a standard peddle first 20A 36V controller
These controllers will "regenerate" when the motor voltage exceeds the battery voltage
I was running 12S Lipo batteries that were discharged down to about 40V
The peak regen current was 14.7A (peak occurred at the time of the incident)
The 20" wheel was turning at 25mph which (apparently) was fast enough to push 14.7A back into a 40V Lipo battery

I'm a tad confused here methods - If I understand the accident scene, you managed to go over your max speed with your controller disconnected from the batteries, then turned it on, thus forcing regen through the FET diodes? I kinda saw it differently from reading your first post, because you talked about just playing with your throttle causing you to go into regen...

Nobody is saying that the regen braking was particularly strong. . . It only takes a little when you consider all the factors.
Walmart forks + no torque arm + strong forward speed + abrupt axle breaking = increased probability of a spun axle.

I understand now that the real culprit here was an inadiquate setup, not necessarily an excessive regen torque involved. I will think of your misadventure when I start doing road tests using regen for sure! I'll have to find/make some good torque arms...
BTW, glad you were not hurt too bad!