Do Nano and Swytch electric upgrades threaten forks?

[bonzobanana]

I'd say this statement is debatable. Apart from the fact that in forums basically everything is debatable, even facts. Including the question wether the facts are actually facts. That's one of the main reasons why forums exist and what causes the traffic in forums.
But as this debate would be completely off topic for the thread and could furthermore easily escalate w/o delivering any value to anyobody I neither see a point in this discussion nor am I willing to have it. That's why I wrote:

You can argue the world is square or the sun is in the sky in the middle of the night of course but facts are still facts. It's not hard to prove that the majority of ebikes in the world are throttle controlled as one example, you have China and India for a start which are easily shown to use such ebikes, that population alone is enough to prove my point before I start looking at smaller countries in Asia etc which typically follow China anyway.

 

[berlinonaut]

You can argue the world is square

You seem unwilling to accept that I am not willing do dive deeper into off topic than we already were. Why is agreeing do disagree not acceptable for you or something that offends you?

 

[Doxup]

All I wade into this conversation having just fitted a Swytch kit to my favourite mountain bike, I simply followed the marketing and wanted to keep my early 2000’s specialised Epic MTB on the road , it fits all bikes they say , no issues … I rode it for about 10 minutes on mixed terrain before this happened , the front dropouts snapped

 

[Doxup]

I was watching a YouTube video about the Brompton Electric and they mentioned that Brompton has strengthened the stem and front forks to allow for the extra torque from the 250W front motor. The Swytch and Nano upgrade kits have similarly powerful front motors but they are designed to be added to existing Bromptons without the strengthened forks. Does anyone think this is a potential issue?

Yes! There is an issue here , devil is in the detail - I have just experienced this with my Specialized Epic MTB - not a low quality bike , but not designed to have such forces applied to the front fork.

 

[presta]

on a human powered Brompton you would not have torque on the fork

Yes you do.

Gravity applies a torque as on the left, and braking as on the right:

Apply the front brake, rock your weight back and forth, and see how the fork flexes.

A brake that meets BS EN ISO 4210-2 will be capable of applying a torque of at least 55Nm on a 16" wheel and 90Nm on a 27" wheel, which is a comparable range of torque to that of an e-bike motor.

 

[Kell]

Yes! There is an issue here , devil is in the detail - I have just experienced this with my Specialized Epic MTB - not a low quality bike , but not designed to have such forces applied to the front fork.

Without being able to see a real close up of the snapped forks, my question would be:

Was there already a crack/some damage there?

I ask as a few years back I snapped one of the crank arms of my Brompton while pedalling. I was staggered that this could happen.

But on closer inspection someone else pointed out that it was fairly obvious there was a crack there that had developed over some time. you could see dirt ingress along the edge of the crack.

I'm not saying this is the case, but have you checked?

 

[ExBrit]

Without being able to see a real close up of the snapped forks, my question would be:

Was there already a crack/some damage there?

I ask as a few years back I snapped one of the crank arms of my Brompton while pedalling. I was staggered that this could happen.

But on closer inspection someone else pointed out that it was fairly obvious there was a crack there that had developed over some time. you could see dirt ingress along the edge of the crack.

I'm not saying this is the case, but have you checked?

Ah, but did you break both crankarms at the same time?????

 

[Doxup]

Ah, but did you break both crankarms at the same time?????

Yes both snapped together, I will share the photo if I’m allowed to on here , the bike is 15+ years old and I have been riding it most days whilst living in Germany over the last few years I’m unable to say whether there were any cracks in the drop outs before.

 

[ExBrit]

Yes both snapped together, I will share the photo if I’m allowed to on here , the bike is 15+ years old and I have been riding it most days whilst living in Germany over the last few years I’m unable to say whether there were any cracks in the drop outs before.

View attachment 678237

Yes, I can see both your dropouts failed. That's what makes me think the motor is to blame. If only one had failed, we might consider a pre-existing crack was partially to blame. So I pointed out that both your dropouts failed but only one of Kell's crankarms failed. Do you know if your dropouts are steel or aluminum?

 

[Kell]

In fairness, I imagine if one dropout snaps the other one would not be far behind...

 

[Kell]

Just for ref, here's the thread about my snapped crank.

https://www.cyclechat.net/threads/snapped-crank.253599/

As you can see in the first pic, there's clean metal and dirty metal. The dirty metal will be where the crack originally developed, and progressed over time. Then it finally had enough and snapped completely.

Given that i regularly have a 40mph+ downhill as well as at that time was bunny hopping up and down one of two kerbs, I consider myself very lucky that it snapped while I was seated, and going uphill, so was dong less than 6mph.

 

[ExBrit]

Just for ref, here's the thread about my snapped crank.

https://www.cyclechat.net/threads/snapped-crank.253599/

As you can see in the first pic, there's clean metal and dirty metal. The dirty metal will be where the crack originally developed, and progressed over time. Then it finally had enough and snapped completely.

Given that i regularly have a 40mph+ downhill as well as at that time was bunny hopping up and down one of two kerbs, I consider myself very lucky that it snapped while I was seated, and going uphill, so was dong less than 6mph.

You are lucky. I had a bottom bracket snap while standing on a hill and woke up in an ambulance.

 

[Doxup]

Yes, I can see both your dropouts failed. That's what makes me think the motor is to blame. If only one had failed, we might consider a pre-existing crack was partially to blame. So I pointed out that both your dropouts failed but only one of Kell's crankarms failed. Do you know if your dropouts are steel or aluminum?

From research I believe the dropouts are an Aluminium / Magnesium alloy and very old, they use Magnesium to reduce weight as far as possible but it is prone to cracking under excess stress. The bike was never designed to have that load on the front wheel. From further research I’ve found that I should have also considered installing a torque arm to spread the load ( Note: I didn’t know this at the time as the Swytch kit manual makes no reference to this option)

I’m considering buying new suspension forks which are E-MTB certified and then installing a torque arm on both sides to prevent this happening again… but obviously I’m very scared that I will never feel confident with it!

 

[ExBrit]

From research I believe the dropouts are an Aluminium / Magnesium alloy and very old, they use Magnesium to reduce weight as far as possible but it is prone to cracking under excess stress. The bike was never designed to have that load on the front wheel. From further research I’ve found that I should have also considered installing a torque arm to spread the load ( Note: I didn’t know this at the time as the Swytch kit manual makes no reference to this option)

I’m considering buying new suspension forks which are E-MTB certified and then installing a torque arm on both sides to prevent this happening again… but obviously I’m very scared that I will never feel confident with it!

I think that's a very important point. People are saying this probably would not happen with quality steel forks. Thanks for the feedback. I would be nervous too.

 

[Kell]

I think if you buy something designed for the motor, you'd be OK.

Like mentioned before, there may be some torque acting on the front dropouts under normal (pedal powered) operation, but they were never designed to cope with housing a driven wheel.

I guess it's the opposite problem to when you install disc brakes on forks that weren't designed for them, you'd need to put the torque bars on there too.