Peoples thoughts on my (planned) first build?

[Rico_Kilo]

Hi Everyone, I've been planning and researching my first electric bike build. I've tried to balance a powerful enough motor and battery against a cost effective build; using my old pedal bike frame.

I think I've researched enough to be at the stage of ordering my parts and start the project (famous last words) but before I do I though i would put it out there to this experienced community to see what you think. As i do have a few Q's and not sure if it will work.

So the planned set-up:
My old hardtail mountain bike frame, has front suspension and caliper brakes

Ebay 48v 1000w 26" rear hub gearless brush motor conversion kit, twist throttle, pedal assist etc (I imagine most of you are familiar with these)

Probably a 48v 15Ah triangle battery to fit into the triangle of the frame.

Questions:
Firstly is there a reason Im overlooking that this won't work?

Secondly am I being silly thinking caliper brakes will be sufficient to stop or do i need to put a disk brake on the rear? The frame isn't particularly modern. Can disk brakes easily be fitted to any frame on the rear wheel?

I'm considering trying to spend more on a 52v 20Ah battery. Is this worth it or a waste of money/power?
As I understand it increasing the batteries volts should put less strain on the motor and maybe provide a little more acceleration?
Also increasing the Ah should increase the range/battery time?

Hopefully you can put me right if i'm completely of track. Happily accept opinions, feed back an suggestions. Also mild ridicule if Im being silly for thinking this will work.

Rico

 

[Benjahmin]

And another person falls for the 1000w label.

It's a direct drive illegal motor. Good for high speed on the flat, highly inefficient at low speed and crap at hill climbing. It will eat your battery. To deliver a 1000w your battery would need to give a constant 20A. Good luck with that.
You will get greater torque and efficiency from a legal 250w geared hub and your, 52v 20Ah, battery should give you between 50 and 100 miles, depending on terrain and what condition your legs are in !

 

[Nealh]

Use a 36v 250,350 or 500w geared hub with your battery choice and a 36/48v dual voltage controller it will be better then the D/D hub. If you have a freewheel gears instead of a cassette you could always get a 800w geared hub. Usually for the good stuff you have to get direct from China sellers though Woosh are getting some 48v hub kits soon.

 

[Deleted member 4366]

Those kits work. They're very heavy, so forget about pedalling without power. They have about the same power and torque as a good 250w system up to about 15 mph. Once they get past 20 mph, they work very well, taking you up to about 30 mph. That's assuming that you have the more common 30 mph windings. Some will go past 40 mph, but are not nearly as good as the slower ones at low speed. Make sure that the seller makes it clear which speed version you get.

Your brakes will be hopelessly inadequate. Both the speed and weight will conspire against them. They're barely adequate to stop the bike at an average speed of 10 mph. Imagine what they'll be like trying to control substantially more weight at 2 1/2 times the speed. With one of those motors, the minimum you need is a hydraulic disc brake on the front. I just put a pair of Shimano XT brakes (£150 a pr) on two bikes with those kits because the owners realised that the previous brakes weren't up to the job.

You get about 1 mile per amp-hour of the battery if you use the power that's available. There's no point in using them with the power turned down because if that's what you're going to do, there's much better solutions.

Finally, those kits are illegal. You can get really good power from a smaller and lighter legal geared motor if you run with 48v.

 

[anotherkiwi]

Secondly am I being silly thinking caliper brakes will be sufficient to stop or do i need to put a disk brake on the rear? The frame isn't particularly modern. Can disk brakes easily be fitted to any frame on the rear wheel?

The front brake is the important one you can put a Magura HS11 on there and it will stop just fine.

A good quality 250 W hub motor your 52 V battery and a 15 Amp 48 V controller will be much better than a 1000W direct drive hub.

 

[Deleted member 4366]

The front brake is the important one you can put a Magura HS11 on there and it will stop just fine.

You need to change your frame of reference. Those brakes are designed for stopping light-weight bikes from 15 mph. If you try and use one to stop a 35kg projectile travelling at 30 mph, either your brake blocks will melt or the rim will wear through by the end of the week. I can tell you that rim brakes on a bike like that are just not going to work.

 

[anotherkiwi]

My Magura blocks are the original ones and have over 5900 km with still a bit left... On the other hand the Avid rear brake blocks need to be changed after 2000 km and I don't use the rear brake much at all. My projectile is over 25 kg and they stop me just fine from well over 30 mph (57.2 km/h on the way to the station last week).

I get your point about the rims and am upgrading the Chinese 28" rims to DT Swiss 535 28" rims in the coming weeks. That said the Italian made 26" rim from my previous bike the HS11 was mounted to with 3600 km of hydraulic brake wear is still quite sound.

I think you should look at Magura hydraulic rim brakes again, you may be pleasantly surprised!

 

[Rico_Kilo]

Hi Everyone, thanks lots of good feedback here, and just a small amount of ridicule. Come on Benjahmain which of us hasn’t seen something new and fun and thought “yes, I will go for the seemingly most powerful set up straight off; boys and their toys ay!”

So, I’m glad I asked first before ordering and clearly in need to go back to the drawing board and recalculate.

Just for the record an additional detail missed from the first post:

The control box advertised two settings, a 250w road setting and an off road 1000w setting. So I was thinking I would have a good road bike with plenty of potential distance (Benjahmin suggested between 50-100 miles) but a fast (mainly throttle powered) off road bike for fun fast traveling around the private farm where I work.

A few more questions and answers would be helpful for my re-design:

Clearly, I will be sticking to the road restrictions, but I would like to be able to exceed 15mph for fun off-road. I’m gathering from your replies that the 1000w setting/set-up won’t have the torque/low end acceleration to be fun on off-road grassy terrain or slight hill climbs?

d8veh, a good break down of the proposed setup and oversights, thanks. Sounds like the proposed setup is kinda of a waste of potential power/speed (and presumably potential distance) until the motor is running over 20 mph. With that and Neath’s comments in mind:

So, bottom line a lower volt and watt hub would be better. From my newbie calculations/understanding reducing both V & W on the motor should increase torque/speed and travel distance/battery drain.

A 36v set up with a 250w / 500w setting sounds like it might be more suitable. What kind of torque/low end acceleration, max speed and distance might I achieve out of a 36v 500w motor? Would a 36v 750w still be too overpowered now I have clarified terrain and bike purpose?

BRAKES!!!!!

Oh what an optimistic fool!!! Well it was worth an ask as I would have liked avoiding the cost of disk brakes to the build (extra money ). I’ve seen clamp sets to attach disk brakes to any frame that doesn’t have the correct fittings, do they work, or do I need a new frame really? I don’t think the one I have will take disk brakes, it has screw hole on the rear struts but they seem too close together for brakes, maybe pannier frame attachments (see photo).

Thanks for answering the previous questions.

It seems that a lower volt/watt motor will give me better torque/low end speed which will ultimately lead to a better average speed and distance. Especially when coupled with the original battery which would fully use the motor capabilities and increase range?

Am I still missing the point?

Thanks again for the opinions, feedback and suggestions.

 

[Rico_Kilo]

 

[Deleted member 4366]

You can change the forks to disc brake forks if you don't want to change the whole bike.

48v is good. It's just that those big direct drive motors really need 35 amps to bring them to life and those cheap kits are much lower than that. You'd be lucky to get 25A out of the battery, and even at that current, the battery will soon wear out.

There's no such thing as a 250w switch because there's no definition of what 250w means. The motor is illegal no matter how you run it, so no point in having a "250w" switch.

Take any 36v 250w geared hub-motor and run it with a 48v battery and controller. You'll get a much nicer bike than one of those big DD kits. The Q128 is a nice motor, but by the time you've bought the battery and controller, the total cost comes to about £600 - worth it though.

 

[soundwave]

https://www.ebay.co.uk/itm/2017-HPC-Crystalyte-The-Crown-GEARLESS-e-bike-Electric-Bike-Hub-Motor-60-MPH/122018434932?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

 

[Nealh]

The Q100H or C version is rated 350w, couple it with a 17a controller will give 595w max or 700w with a 20a controller @36v. At 48v stick to 17a (816w) or less other wise you will eventually strip the gears.
Q128C 500w or H version 800w will both handle more watts.

Q100 comes in 201,260 & 328rpm respective mph@36v is approx. 16, 19 & 25, the first two are ideal for hill climbing.
Q128 comes in 201 or 328rpm though the 201 is probably mislabelled as mine @36v easily does 19 - 21 mph so is more likely a 260rpm winding. Both hub versions speeds are the same irrelevant of the wattage rating.

Q100 approx 2.2kg , Q128 3kg.