First build spec

[Richardab]

OK i have had an interesting few days reading this forum. Much better informed but still loads to learn.

Could i put out a ‘brief’ and possible spec list for your comments

My weight 80kg
Current daily commute is 16 mile round trip, 5 days a week, plus extra in the summer, usually average arond 3-4000 miles year, been doing that for 12yrs now.
This is now mostly done on a carbon singlespeed
I am thinking of changing my commute distance to 40miles round trip, i have done this sort of commute quite a bit as one offs, but it would be a big ask to do it 5 days a week, so i am looking at ebikes for help.
My current commute is a bit short and easy so am very keen to ride at least as hard as i do now, if not a bit harder, i would just like to cover further distance in a reasonable time.
I understand the “il”legalities, i am not concerned, i ride at 20-25mph unassisted, i want to achieve similar speeds with some help to cover the greater distance on a regular basis and also maintain reasonable speed on hills rather than slowing my average speed down (currently 15mph, i’d like to be able to average 20mph+)

I mostly ride singlespeed, lighter, less friction, cheaper, less maintenance, less fragile taking it on the train (which is the other half of my commute). From my previous query it seems its feasible to make the SS into an ebike. I guess i would need to regear it so that 20-25mph continuous was not too spinny, but i am assuming the motor will help overcome the hills with a bigger gear.

I have a couple of possible candidate bikes, but i am most excited about converting the carbon singlespeed commuter into a stealthy ebike, as i built it especially for commuting, its light, comfy, dry, fast and has good brakes. Pic attached

I assume i am looking at a rear hub motor, seems the q128c gets good reviews and i see it at bmsbattery as hub only which suits me so i can build it into a matching wheel.
Battery sounds like 48v, i am not sure on amp hrs, should i be aiming for the 40 mile round trip or charging at work and home. I am planning on putting, battery, controller, lcd in my large saddlebag, with just the PAS and assist control (and motor) on the bike. The bag has a weight limit of 10kg, currently it only carries a few tools and bits of clothing so plenty of capacity, but i guess it will be noticably rear heavy which is a bit pf a concern, what does battery/controller/screen weigh? No thumb throttle or brake switches. I would need a decent ‘connector’ between the saddlebag and the bike that can be regularly disconnected, does that exist.

I have no idea about controllers, it seems KT get mentioned alot but where do i get these from and what size? The LCD3 screen gets mentioned alot, again where do i get this. Any particular PAS required, i do have a carbon sram gxp chainset going through an eccentric bb so i can imagine some creative fettling is required.

Any input welcome...is it possible, am i on the right track?

 

[Deleted member 4366]

Carbon fibre is generally not good for conversion because the motor puts a torque around the drop-outs, which the frame is not designed to resist. You'd be better keeping that bike as it is and getting an aluminium one.
Q128C is for cassette gears. For single-speed, it would be the Q128H, though the Q100H is 1.5kg lighter and probably plenty strong enough for what you want. The speed is always a problem. The 328 rpm Q128 has power to hold mid 20s. To get the 328rpm, you need the 328 rpm 48v one at 48vv or the 201 rpm 36v one (it's actually 260 rpm ) at 48v. The 36v Q100H comes in 201 rpm and 260 rpm flavours, which will be 260 rpm and 328 rpm at 48v. I'm not sure whether 328 rpm will be a bit too fast for it. It would probably be OK, but I haven't tried it.

To run at 20 mph with moderate steady pedalling takes about 250w from the battery, so you'd need a minimum of 500wh to go 40 miles.

You get the motors from BMSBattery.com, but they don't have a 15A sinewave 48v controller, so you have to get that from Aliexpress or PSWPower.com.

 

[anotherkiwi]

Don't ruin a lovely bike like that!

Find another one for your conversion.

Crossed with d8veh...

 

[Richardab]

It’s true, that was my initial thought that it’s too nice to ruin...but in truth it was solely built for the commute I do. If I had another bike (got too many as it is!) and IF it was a success I would never ride the carbon commuter, all my leisure riding is mtb nowadays. The IF is important because if it was not workable then it would have been a waste of a nice bike (I am assuming the mods would be irreversible but actually I don’t see they would?)

I do have an alternative bike but it’s not as good, heavier, bit too small but mostly it has a hub gear with in built drum which I would lose snd need to hodge a disc on there which is not ideal

When you talk about strength of the carbon frame are we talking about tearing the drop out out or the stability of the rear triangle. The frame is a CX frame so expected to cope with a bit of abuse and has steel dropout inserts plus is designed for disc brake so I would assume the forces involved in braking hard by the calliper mount and the forces from a torque arm would be similar ie you can probably slow down quicker than accelerate

The current hub is a cassette free hub so I have no problem using the q128c as I generally find free wheels limiting in tooth size and quality. It’s just a single cog slid over the cassette with spacers either side to get chain line correct. Is there any downside in using the q100h, it’s less powerful I assume will it be more stressed and less reliable. I’d rather stick with the q128c if it’s going to be less stressed although the weight saving of the q100 is attractive

500wh for 40miles is a useful guide. An 11.6amphr battery gets me that but do I have to figure in a percentage of useable energy I assume you don’t run batteries 100%

 

[Woosh]

most geared hub kits have noload speed about 24mph, they are suitable for maintaining 20mph on the road. You'd need a crank drive kit to go over 20mph average.

 

[Deleted member 4366]

most geared hub kits have noload speed about 24mph, they are suitable for maintaining 20mph on the road. You'd need a crank drive kit to go over 20mph average.

No load speed of a 328 rpm motor, like the q100 and q128, is around 30 mph in a 700c wheel, so good power up to the mid 20s.

 

[Deleted member 4366]

It’s true, that was my initial thought that it’s too nice to ruin...but in truth it was solely built for the commute I do. If I had another bike (got too many as it is!) and IF it was a success I would never ride the carbon commuter, all my leisure riding is mtb nowadays. The IF is important because if it was not workable then it would have been a waste of a nice bike (I am assuming the mods would be irreversible but actually I don’t see they would?)

I do have an alternative bike but it’s not as good, heavier, bit too small but mostly it has a hub gear with in built drum which I would lose snd need to hodge a disc on there which is not ideal

When you talk about strength of the carbon frame are we talking about tearing the drop out out or the stability of the rear triangle. The frame is a CX frame so expected to cope with a bit of abuse and has steel dropout inserts plus is designed for disc brake so I would assume the forces involved in braking hard by the calliper mount and the forces from a torque arm would be similar ie you can probably slow down quicker than accelerate

The current hub is a cassette free hub so I have no problem using the q128c as I generally find free wheels limiting in tooth size and quality. It’s just a single cog slid over the cassette with spacers either side to get chain line correct. Is there any downside in using the q100h, it’s less powerful I assume will it be more stressed and less reliable. I’d rather stick with the q128c if it’s going to be less stressed although the weight saving of the q100 is attractive

500wh for 40miles is a useful guide. An 11.6amphr battery gets me that but do I have to figure in a percentage of useable energy I assume you don’t run batteries 100%

In that case, a hub motor will probably be OK, especially if you can fix the torque arm to the disc mount.

You need to think about the weight. A Q128 and a 50 cell battery will add 7.5 kg to your bike

 

[DynatechFan]

To answer the query about controller and LCD3 they are both pretty small, maybe 10cm x 7cm x 2cm (a guess cant get at mine to measure right now) and weight little. The LCD3 is all plastic, the controller I have is a circuit board inside an aluminium extrusion - couple of hundred grams all in maybe

If your eccentric BB is similar to our off road tandem it shouldn't be a problem - the PAS usually goes behind the LH crank on the axle

 

[Woosh]

No load speed of a 328 rpm motor, like the q100 and q128, is around 30 mph in a 700c wheel, so good power up to the mid 20s.

you need a combination of speed and power. These Q100 (120mm motor) and Q128 (140mm motor) will suit some strong pedalers but are really optimised for 20mph on average. If you select a high RPM, the low speed torque will greatly suffer.
The next step up is BBS01 for 22mph, BBS02 for 25mph BBSHD for 28mph.

 

[Deleted member 4366]

you need a combination of speed and power. These Q100 (120mm motor) and Q128 (140mm motor) will suit some strong pedalers but are really optimised for 20mph on average. If you select a high RPM, the low speed torque will greatly suffer.
The next step up is BBS01 for 22mph, BBS02 for 25mph BBSHD for 28mph.

That's why I suggest 48v. It gives 33% more power than what you're used to.

The max RPM of a motor doesn't affect the maximum torque much. You can only see the difference at very slow speed. At 20 mph, the faster motor will give the most torque.

 

[Richardab]

In that case, a hub motor will probably be OK, especially if you can fix the torque arm to the disc mount.

You need to think about the weight. A Q128 and a 50 cell battery will add 7.5 kg to your bike

Ouch the whole bike only weights 8kg now!! I am a bit worried about the rear bias, heres a pic of the bag I want to put the battery and controller in, on the carbon singlespeed's predecessor. This was particularly loaded up, I dont normally carry a quarter of that. If the battery pack was along the bottom or forward side (it fits, I checked dims) I guess it would be pretty much under my bum, a bit high though...although no worse than the day in the pic.

 

[Richardab]

That's why I suggest 48v. It gives 33% more power than what you're used to.

The max RPM of a motor doesn't affect the maximum torque much. You can only see the difference at very slow speed. At 20 mph, the faster motor will give the most torque.

So a 36v motor at 48v is better...any downside? I can run both the q100 and q128 at 48v, but the q100 is smaller and lighter...whats the disadvantage?

 

[Deleted member 4366]

So a 36v motor at 48v is better...any downside? I can run both the q100 and q128 at 48v, but the q100 is smaller and lighter...whats the disadvantage?

The gears in the Q100 are smaller, so they'll wear a bit quicker, but they're very cheap and easy to fit.

The only advantage of a fixie is light-weight, which you don't really need when you go electric. Any normal bike with gears, a Q128c, 48v battery with 12Ah or more and 15A controller will make an excellent commuter bike.

Does the bike in the photo have a 135mm wide rear subframe? It looks a bit narrow to me. A cassette motor needs a frame sprung to about 140mm.

 

[Richardab]

The carbon SS is a 135mm frame.

That was the gist of my question on the earlier thread about singlespeed...will it work as an ebike. Sounds like it would work...but would a geared bike be even better. I can run gears on it, thats what the frame was designed for originally, I just like the simplicity and reliability and lightness of SS (although I take your point with 7.5kg added a few grammes saved by weight weenie parts is irrelevant.)

 

[Deleted member 4366]

Difficult choices. I have a nice carbon fibre road bike that I use for bike rides and exercise, but for for shopping and transport I use my electric bike that weighs 20kg.

I build other electric bikes as experiments, but I must admit that it doesn't make sense to me to have an electric bike like a normal one. You can get a bike that's exactly like a normal one. It's called a bike. If you want assistance, you might as well have a bike that's comfy and meets your transport needs free of constraints. Well balanced light bikes are definitely better to ride, though.

 

[Richardab]

I do very much use my commute as exercise, its not shopping or for leisure. The carbon SS was built for exactly this job, it is an excellent commuter with guards, discs, minimum bits to rust, no gears to gum up or get knocked on the train, but is suited to someone who want to 'exercise'. I have a 'nice' road bike too for sunny days, but find I am on mtb more than road if its for pleasure. The carbon SS is only for commuting, I wouldn't use it for anything else thats why I am keen to use it if poss for the longer commute as otherwise it has no purpose!

I basically want to increase my commute mileage (I will save £1000 a year riding a few stations further along the trainline), without wiping myself out during the week. So I don't see it as functional 'shopping' or getting about bike, I don't want it anymore comfy or cruisey (carbon is pretty comfy anyway). I just want to get further for the same or a bit more input from myself.

But I am worried I spend the money, rebuild it and am dissapointed with the experience or performance or range or the longer commute isnt viable and I have mucked up a nice bike. Thats a hard one for me to gauge with zero experience of ebikes (especially speed pedelecs)

 

[anotherkiwi]

I do very much use my commute as exercise, its not shopping or for leisure. The carbon SS was built for exactly this job, it is an excellent commuter with guards, discs, minimum bits to rust, no gears to gum up or get knocked on the train, but is suited to someone who want to 'exercise'. I have a 'nice' road bike too for sunny days, but find I am on mtb more than road if its for pleasure. The carbon SS is only for commuting, I wouldn't use it for anything else thats why I am keen to use it if poss for the longer commute as otherwise it has no purpose!

I basically want to increase my commute mileage (I will save £1000 a year riding a few stations further along the trainline), without wiping myself out during the week. So I don't see it as functional 'shopping' or getting about bike, I don't want it anymore comfy or cruisey (carbon is pretty comfy anyway). I just want to get further for the same or a bit more input from myself.

But I am worried I spend the money, rebuild it and am dissapointed with the experience or performance or range or the longer commute isnt viable and I have mucked up a nice bike. Thats a hard one for me to gauge with zero experience of ebikes (especially speed pedelecs)

OK that puts it more in perspective. You are a fit cyclist, initially you will be disappointed by the performance, you will have to adapt. For us older lasses and lads having a pedelec is a step towards fitness and like many other I am now able to ride unpowered again when I want to.

What speed do you climb at now on that bike?

We know you will be doing well over the legal cut off speed on the flat without a motor. I have a comfy upright pedlec and roadies pass me when I am doing about 32 km/h on a flat rolling road I use, the clever ones draft me on the uphill sections. If you want to go faster than that you have to over-volt a hub motor or use a mid drive with the right gearing, the second being a heavier option.

Or go really light weight and only use the motor on hills and when you need to relax which means about 27-33 km/h top speed powered. A bike like that would be great with the new ting Xiongda rear hub and a small battery like d8veh linked recently.

 

[DynatechFan]

I am hearing Cost:Benefit:Risk here - maybe you need a decision tree?

With the cost savings you are talking about does that open up the options? eg buy a s/h bike and cheap conversion kit (or borrow? - my local council does 1 month ebike loans) - costs you a month or two of savings - if you hate it sell s/h bike & kit, back to your current ways with an un-messed carbon bike

 

[Richardab]

OK that puts it more in perspective. You are a fit cyclist, initially you will be disappointed by the performance, you will have to adapt. For us older lasses and lads having a pedelec is a step towards fitness and like many other I am now able to ride unpowered again when I want to.

What speed do you climb at now on that bike?

We know you will be doing well over the legal cut off speed on the flat without a motor. I have a comfy upright pedlec and roadies pass me when I am doing about 32 km/h on a flat rolling road I use, the clever ones draft me on the uphill sections. If you want to go faster than that you have to over-volt a hub motor or use a mid drive with the right gearing, the second being a heavier option.

Or go really light weight and only use the motor on hills and when you need to relax which means about 27-33 km/h top speed powered. A bike like that would be great with the new ting Xiongda rear hub and a small battery like d8veh linked recently.

I would think that I have most to gain from an ebike on the hills for sure, the SS is very quick up short steep hills as you dont lose momentum clicking around with gears, longer drags it really slows down. Looking at strava I am doing around 8-10mph on a decent hill so I have a lot to gain from an ebike there. But cruising speed is 18-20mph I would say with bursts higher. Of course on a geared bike this could easily be higher but there are good reasons for a SS bike as a commuter.

Is a conversion with a small motor and light battery that just helps on hills but not on the flat a possibilty? I do like the idea of keeping things light.

 

[Richardab]

I am hearing Cost:Benefit:Risk here - maybe you need a decision tree?

With the cost savings you are talking about does that open up the options? eg buy a s/h bike and cheap conversion kit (or borrow? - my local council does 1 month ebike loans) - costs you a month or two of savings - if you hate it sell s/h bike & kit, back to your current ways with an un-messed carbon bike

I wonder if I could just demo one from a shop for a day? Even a legal one would give me an idea how useful it is on hills. Any recommendations for a demo bike?