Accident with Golden Motor

[Franco1206]

hello here is Franco from Italy! I got from a friend a bicycle with a Golden Motor and short time later I had a bad accident because the front wheel blocked abruptly. It happened like this: a was driving downhill without giving power, suddenly I heard a LOUD noise coming from the motor (like rattling) and as I just touched the brake (only touched!) the bicycle blocked all at once and I fell to the ground enjuring head and ribs.
I only would like to know how it could happen (brake failure? elecronic failure?) because I opened the motor and I saw no recognizable malfunction or corruption. obviously I cannot trust the bicycle and the motor anymore without knowing what it caused my accident.  :-((
thank you very much. 

[Bikemad]

Hi Franco andto the forum.

Sorry to hear about your unfortunate accident and injuries, but could you please provide a bit more information including which motor and battery you have and whether the motor has an internal or external controller?

What size wheels does your bike have and how fast were you going down the hill?

Does the motor still work, or is it difficult to spin by hand since the incident?

Did the front wheel slide on wet slippery loose ground or was the surface dry with plenty of grip?

Alan
 

[Franco1206]

hi Alan thank you so much for your friendly answer! concerning motors I am a bit a dummie, so I hope it is right if I attach photos. the size of the wheel shold be about 25 inches (rim). I didn't go too fast, I would say moderate and the ground had plenty of grip (asphalt, dry). the accident happened in 1 second: luod rattling noise, sudden block (like smashing against a wall!) and me (completely surprised) threw to the ground. I lay unconscious for a while. I just would like to know, how and why this could happen! nearly ghostly, since I am a very skilful biker...
grazie & ciao

[Franco1206]

dear Alan, to make it easier for you, only one final question (not binding for you obviously): do you think, motor or brake "could" have abrupt block the front wheel or shall I rather look for a completely other cause? just only to decide, if I still can trust the motor.......
thanks again
Franco

[Bikemad]

Hi Franco,

It's difficult to say for sure whether the locking of the front wheel was caused by a mechanical or an electronic fault, but I can say that you have a Magic Pie motor which is a version III or later because it has the exposed controller.
However, I am very puzzled by the rusty steel centre section on the removed side cover as this cover is usually solid aluminium which does not rust. 

Does the motor still work, or is it difficult to spin by hand since the incident?

As you have not answered this particular question I will try to cover both options:

1) If the motor has stopped working completely and was now very stiff to turn (prior to dismantling it) it could most likely be attributed to controller failure.
If the controller failed with two or more MOSFETS in a short circuit state, this could have caused the severe braking effect that you experienced.
Another forum member experience something very similar to you on a much earlier version of the Magic Pie. Check out this thread for more information.

2) If the motor still ran normally and the wheel rotated freely after the accident, it is less likely to be attributed to the controller.

I have been carefully studying the pictures of your motor and the right hand side cover appears to show signs of severe rubbing, as if something could possibly have been jammed between the side cover and the front fork:



Was the front motor axle still securely fixed to the fork legs or did the dropouts break off during regen causing the wheel to break loose and jam in the forks?



Does your bike have aluminium forks, and if so, were any torque arms fitted?



The only other thing I can see that doesn't look correct is a small piece of magnet appears to be missing (circled below) inside the motor ring.



If this had come loose it could have jammed between the magnets and the stator assembly, but I would expect the tiny magnet part to simply break up rather than jam the wheel up completely. 

Alan
 

[Franco1206]

Hi Alan! I cannot express how happy and thankful I am with your precise investigation! You are really a professional! Indeed you have found the cause of the accident: “the right hand side cover appears to show signs of severe rubbing, as if something could possibly have been jammed between the side cover and the front fork”. Look at the pic of the inside of the front fork I have attached! No doubt! This explains the rattling noise I heard coming from this side of the motor! And those days there was on that road a traffic of heavy trucks with building materials which could easily have lost something. By the way: the wheel rotated freely after the accident.
So I’m glad that I can trust the motor and the bike again, the only thing I would say (out of this experience) is that the lack of space between the motor and the fork can become dangerous in similar situations. The large size of the covering pane can easily cause something to get stuck!
Thank you again and good-bike!
Franco
P.S.: I forgot to say that the wheel was out of the forks after the accident, but the fork legs are not broken (thanxx for the tip concerning the hoseclamp!! very important!).

[Bikemad]

P.S.: I forgot to say that the wheel was out of the forks after the accident, but the fork legs are not broken.

The forks may not be broken but the dropouts on your forks have been badly spread apart (as shown below) by the twisting force of the axle, both under power and during regenerative braking.





Unfortunately, I am now pretty confident that your accident appears to be a direct result of not having suitable torque arms to withstand the tremendous torque being applied to the dropouts through the axle flats, and the front wheel axle would have twisted out of the dropouts as soon as you pulled the brake lever (front or rear) far enough to activate the regenerative braking.

When the axles spins out of the dropouts, the weight of the bike would instantly cause the top of the forks to jam against the front tyre causing the bike to flip over forwards, sending you flying over the handlebars and onto the road at the same time. 

You need to understand that a conventional front wheel axle on a standard pushbike does not apply any torque whatsoever through the dropouts, because it cannot transmit a rotational force through the axle bearings (even when braking), so the dropouts are neither designed nor intended to withstand torsional forces, which is why suitable torque arms are such an important item on ebike conversions.

Check out this post to see just how much torque can be applied through the axle of a Magic Pie motor under full load. 

Alan
 

[Franco1206]

hello Alan, please allow me say again how thankful I am for your help. in a nutshell: I had just got the bike a few weeks ago from a friend who years ago had installed the Golden Motor in a pushbike. in the meantime the bike had been ridden a lot and the dropouts were certainly worn out. I didn't know that. so it certainly happened that an object that got stuck kicked the wheel out of the dropouts. I will immediately order the double hoseclamp that you have recommended to me. and this is also important for all bikers who read this thread! thank again and goodbike!

[Franco1206]

oh sorry a very last question: coud be safer if I would disconnect the regen braking perhaps of the front wheel only?

[Bikemad]

so it certainly happened that an object that got stuck kicked the wheel out of the dropouts.

As the wheel was out of the forks after the accident, and the dropouts are badly spread, I no longer think that something got stuck between the wheel and the fork, as an object trapped between the side cover and the fork should not cause the wheel to come out of the dropouts.

I now suspect that the wheel began to initially work its way out of the right hand dropout (during repeated acceleration and braking) until the right hand side cover began to rub against the fork.
This would explain both the "LOUD noise coming from the motor (like rattling)" and the heavy grinding marks all around the side cover where it has obviously rubbed against the inside of the forks after studying the picture of your forks.

The torsion force on the axle from the last application of the brakes was sufficient to twist the already loosened axle right out of the dropouts, causing the wheel and tyre to then jam against the fork (and possibly the frame downtube too) which would have stopped the front wheel instantly, and we already know what happened at that point. 

oh sorry a very last question: could be safer if I would disconnect the regen braking perhaps of the front wheel only?

Disconnecting both of the brake switches to disable the regen on the front wheel is not a good idea, as you would also be disabling the safety power cut-off feature when either of the brakes is applied. This could be very dangerous if your motor suddenly became stuck on full throttle due to a wiring fault or water in the throttle etc..

As long as the axle is properly secured to the forks using suitable torque arms, you should be able to use the regen function without worrying about the wheel coming loose again. 

Alan
 

[Franco1206]

dear Alan, at this point I really "have to" write again. you must be Sherlock Holmes! exactly like you say it must have happened! now I have unfortunately another more question: I would order two hoseclamps from Canada for both sides, do you think that would be enough or do I have to replace the whole fork because of the spreaded dropouts? I ask you that without requiring from you a guarantee of course ...

[Bikemad]

Hi Franco,

As your forks have steel dropouts, you should be able to carefully squeeze them back to the correct shape by using a bench vise (or perhaps a large hammer) so that the axle washers and torque arms have something to clamp against correctly when the axle nuts are fully tightened.

If you cannot get the dropouts back to their original shape, it might be best to find another set of front forks.

Alan
 

[Franco1206]

GREAT! thank you again so much!
Franco