Conversion kit for my Crescent

Bikes4two · Aug 12, 2020

For front vs rear hub, there's plenty of comment on the forum but start with this recent posting here.

The general view seems to be a rear hub is preferred unless you have a specific reason for a front hub and certainly with motors of the power you are looking at, the rear hub motor definitely gets more votes!

vfr400 · Aug 12, 2020

There are a lot of different Crescent bikes and nearly all of them are unsuitable for a 500w or 1000w front motor. Maybe you could start by showing us what you have instead of leaving us to guess. Also, we need to know if it has free-wheel or free-hub gears, and how many.

vfr400 · Aug 12, 2020

OK, so you need something like a rear 500w geared cassette motor running at 48v to get what you want. You'll probably have to buy you stuff from China, either direct from the re-sellers or via Aliexpress. Your budget looks a bit tight.

You could get one of those cheap direct drive motor 1000w kits, which are very heavy, but you will have to pay around 400 Euros just for the battery and you'll have to throw away all your nice gears/shifters, etc, and replace them with a cheap 5-speed or 7-speed set. IMHO, if you want to use a motor like that, you'd be better off using a cheap steel-framed bike to convert.

That brings me to the next point. There's no way your brakes are going to cope with the additional mass and speed after fitting a kit capable of doing what you want. For that, you need hydraulic disc brakes, so you need to find a new donor bike with disc brakes.

Sorry for the bad news. Your Crescent bike is just about OK for converting with a 25km/h kit, but to be honest, I wouldn't even do that with those brakes.

vfr400 · Aug 12, 2020

mt247 said:
Thanks for input I'll screen for new bike and sell this one. Also I red about kool stop branded v-pads which are supposed to be really good and on par with disc brakes. Aliexpress/Ebay is fine for me to order ebike kit. That 48V 500W geared motor sounds good to me.

Something like this? https://www.aliexpress.com/item/32961457003.html

I'll might buy Tunturi rx500 hybrid bike for my project after I manage to sell my old bike. 360 view here: https://www.tunturi.fi/tuote/arkisto/2019/hybridipyorat-2019/rx-500-2018-19/
View attachment 37720

Get yourself a back-pack and put about 8kg of potatoes in it, then go and find a steep hill that will get you up to 40 km/h. see how well your brakes work. Kool-stop pads will make about 10% difference for the first 2 seconds, then they'll melt just the same as your present ones.

Bikes4two · Aug 12, 2020

That's an interesting point of view about the brakes, the 8kg of potatoes, 40km/hr etc. and the donar bike which is using 'V' brakes

In determining if those brakes might be sufficient, I'd like to offer my own experiences and that is,
> I have done a fair few thousands miles cycle camping, average kit weight 12Kg (plus me at 90Kg - on a good day

) on a Dawes Galaxy (non electric) with canti-lever brakes (which are on a par with the V brake if set up correctly).
> My trips have included many hilly areas including some of the higher Cols and passes in the French and Swiss alps where descents have in some cases have been loooong and steep and I have never had issues with stopping, brake blocks failing or rims over heating (although I have had to cool the rims in a stream once after a long descent in Portugal, but no brake failures though).

So yes, I think the loaded rucksack on a steep descent is a very good idea for you to see how your brakes perform and to enable you to make a judgement on efficacy and is maybe something you should try before discounting the 'V' brake arangement.

Finally, that's a nice looking donor bike - if you wanted to use it but were not confident in the stopping power of the 'V' brake, you could always consider changing to something like Magura hydraulic rim brakes - we have the Magura HS31 on our tandem which with camping kit and two persons comes in at well over 200kg and stops fine.

vfr400 · Aug 12, 2020

Bikes4two said:
Finally, that's a nice looking donor bike - if you wanted to use it but were not confident in the stopping power of the 'V' brake, you could always consider changing to something like Magura hydraulic rim brakes - we have the Magura HS31 on our tandem which with camping kit and two persons comes in at well over 200kg and stops fine.

A new donor bike would be cheaper than two sets of hydraulic rim brakes, and disc brakes are better anyway.

sjpt · Aug 12, 2020

I've found V brakes very effective; work well on our tandem. I can see that they would not be suitable for a long decent because of heat. I much prefer them to cantilever ones; for me they work more effectively and
are easier to adjust.

I do not like the Magura hydraulic rim brakes on the Motus. An absolute pain to adjust and they don't have such a firm stopping action as V brakes. (Maybe they need bleeding?)

I've never had disk brakes (hydraulic or cable) so can't compare. From what everybody says they are superior.

Nealh · Aug 12, 2020

Aeikema sell a 500w 48v cassette model or a 800w freewheel model both the same size.
The 800w is only a slower wound hub though.
Which rpm model you buy not only depends on the speed you want but also terrain, do you have any hills to climb ?

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vfr400 · Aug 12, 2020

An average rider on a bike like OP's might average around 12 mph. His brakes are probably adequate for that.

When he puts a kit on that bike and starts averaging 25 mph, he will have approximately 5 times as much kinetic energy, which will require 5 times as much braking to dissipate it. Imagine that bike with 5 sets of caliper brakes on each wheel. That would give him the same braking efficiency as he already has. Some of you guys have got no idea about basic physics.
KE=1/2mV x V

Bikes4two · Aug 12, 2020

sjpt said:
I've found V brakes very effective; work well on our tandem. I can see that they would not be suitable for a long decent because of heat. I much prefer them to cantilever ones; for me they work more effectively and
are easier to adjust.

Irrespective of V or Canti or Magura rim brakes, a 3rd brake on a tandem is desirable for long descents to 'share' the load amongst all braking surfaces. On our tandem the 3rd brake is a rear disc - that combination has worked well for us.

I do not like the Magura hydraulic rim brakes on the Motus. An absolute pain to adjust and they don't have such a firm stopping action as V brakes. (Maybe they need bleeding?)

I think you've been unlucky with your Maguras - I've had ours on the Tandem for 8 years and many thousands of miles and have only had to change the brake blocks - no adjustments or bleeding in that time.

I've never had disk brakes (hydraulic or cable) so can't compare. From what everybody says they are superior.

That's why forums are so good - a great platform for debate. I have had disc brakes (cable and hydraulic) and yes they are good and easier on the fingers if descending a lot (as in hours at a time over several days), but irrespective of the make or model I've had, disc rub during free wheeling is something that has plagued me (probably an adjustment thing).

You do hear of discs overheating and possibly warping on long descents but I've no experience of using them like that so I can't really comment as to whether that is a real risk for most cyclist.

vfr400 · Aug 13, 2020

mt247 said:
This looks good here is my commute route:
View attachment 37757

Is there version with spokes+rim already attached to motor? I think it's too difficult task to do myself.

Q128C-135mm 500W Rear Driving EBike Hub Motor Wheel RPM 201 Voltage 36V

Q128C-135mm 500W Rear Driving V-brake, rim-brake, Disc-Brake compatible E-Bike Hub Motor Wheel. Waterproof hall sensor connector.

bmsbattery.com

wheeliepete · Aug 13, 2020

mt247 said:
Is there version with spokes+rim already attached to motor? I think it's too difficult task to do myself.

Postage from China is a bit pricey for complete wheels as you will see. Ask around your local bike shops, assuming you have some, for a decent wheel builder. Should work out cheaper.

Bikes4two · Aug 13, 2020

The price of a hand built wheel then? For guidance
> Spa Cycles charge £99 for a 36 hole wheel on 26" or 700c rim with a standard Deore hub - I don't know if they build wheels onto hub motors though
> If you were buying the rim (around £25 plus p&p) and spokes (£20) plus then someone's time to build the wheel, you can see that £70 might be a keen price

Both of these options likely give you a better quality rim and build than the factory built wheel from China, but it comes at a price.

So either factor that against the extra postage costs from China vs buying the motor already laced into a rim from a UK supplier.

Alternatively, learn to build your own wheels - not straight forward of course but it is not the dark art you might think it is either.

vfr400 · Aug 13, 2020

Most bike shops won't touch it because a hub-motor doesn't fit their fixture. The cost is about equal between buying it built and getting a shop to build it. In fact the shop will probably be dearer because the costs are close when you build it yourself.

Conversion kit for my Crescent

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