Would this bike be suitable for ebike conversion

[Julie]

Hello

I have a nice hard tail mountain bike that i've not used for a few years, and i'm considering converting it into an electric bike for commuting, i'd like to add a geared rear hub motor. I don't want to do any permanent modification to it, for example i don't want to drill holes in the frame or file down the dropouts.

I don't want a rear rack mounted battery, i'd want one mounted to the frame but i'm not sure i'd have room as it's a small frame.

I've added arrows to the frame pic to show the position of the water bottle mounts, I'd love opinions on the viability of this conversion, thanks for reading.

 

[Woosh]

the frame is a bit too small for an HL kit I think.
Cut a piece of cardboard 37cm x 10cm to represent the downtube battery - see if you can place it inside the triangle.
There is a possibility to mount the kit to the underside of the downtube like this:

 

[Julie]

Thanks, you were right, there is no way that is going to fit. Do the batteries slide in from the side, not that it would fit this bike, but i'm just wondering what type of frame set up i would need if i buy a suitable bike for conversion.

 

[Julie]

If i mounted on the underside of the down tube would i have to drill holes in the frame to mount the battery?

 

[Woosh]

yes, you will need to fit at least 3 x M5 rivnuts, likely 4 or 5 rivnuts. 10 minute job with the right tool.

They are easy to do, drill 6.5mm holes and use a tool like this:
https://www.ebay.co.uk/p/86pcs-Threaded-Nut-Rivet-Gun-M3-m8-Insert-Tool-Riveter-Rivnut-Nutsert-Riveting/4021720328

You don't need the gun, you can do it with just M5 bolt and a couple of nuts but it's always easier with the right tool.

 

[Julie]

Thanks, i don't really want to damage the frame, as it's a nice bike. If i were to buy a cheap bike to convert to an ebike would this type of frame be more suitable? I'd be ok with drilling holes in the bike if i were to buy a cheap one, in this design would the battery be mounted on the seat tube or down tube?

Would it be possible to mount 2 batteries to this type of bike, even though only one would be connected, and i'd need to manually swap them over? i need to batteries for my commute.

 

[Woosh]

Would it be possible to mount 2 batteries to this type of bike, even though only one would be connected, and i'd need to manually swap them over? i need to batteries for my commute.

how far do you want to go? with a 17ah rack battery, you can hit 100+ miles on pedal assist with a rigid fork and 700-28 tyres.

 

[Julie]

I’m currently doing my 28 mile each way commute using a Bosch mid drive bike, I use maximum assist (turbo)all the way and I get one way with about 20% of a 500w battery left, I use 2 batteries as I can’t charge at work.

I need to be peddling with maximum assist both ways as when I get to work I spend 11 hours standing up in a factory, so need to minimise fatigue on the commute.

 

[Julie]

I have done the commute once using a freego wren with a 16ah battery, the power started to fade about 20 miles from home on the way back, and the battery died about ten miles from home.

 

[Nealh]

Thanks, i don't really want to damage the frame, as it's a nice bike. If i were to buy a cheap bike to convert to an ebike would this type of frame be more suitable? I'd be ok with drilling holes in the bike if i were to buy a cheap one, in this design would the battery be mounted on the seat tube or down tube?

Would it be possible to mount 2 batteries to this type of bike, even though only one would be connected, and i'd need to manually swap them over? i need to batteries for my commute.

View attachment 26090

Cheap bike as in the red one you show uses hub gears so a rear hub motor is no good.
Use a GSM mid drive with a KT 17a controller and lcd3.

 

[Artstu]

how far do you want to go? with a 17ah rack battery, you can hit 100+ miles on pedal assist with a rigid fork and 700-28 tyres.

ooh I'll have one of those, if only it were true.

 

[Woosh]

ooh I'll have one of those, if only it were true.

have you tried an electric road bike with rigid fork, large wheels and skinny tyres?

 

[Woosh]

I have done the commute once using a freego wren with a 16ah battery, the power started to fade about 20 miles from home on the way back, and the battery died about ten miles from home.

there may be specific problems with that bike like the battery has a bad block of cells.
When you use a bike for commuting, one leg may use more battery than the other because of elevation but by and large, power consumption is pretty much proportional to the cube of speed. This is a fundamental aspect to assess which battery capacity you require. There is a drag calculator on this site:
http://kreuzotter.de/english/espeed.htm

The example below is for a roadster going at a decent 15mph, note the power required is only 160W (without pedaling). Contrast that with the power consumption around 800W of a low cost MTB fitted with a BBS02 ridden at twice the legal speed.

 

[Artstu]

have you tried an electric road bike with rigid fork, large wheels and skinny tyres?

Nope, 100 miles on 17ah is pie in the sky though, like I said if only what you say were true.

 

[Woosh]

Nope, 100 miles on 17ah is pie in the sky though, like I said if only what you say were true.

you should read members' reviews of the Woosh Karoo.

 

[Artstu]

you should read members' reviews of the Woosh Karoo.

I have, ok one reviewer got a one-off 75 miles and another 79 miles, still 21 and 25 miles shy of your exaggerated claim of 100 miles.

ETA, ah I see they may have been the 13 ah battery. so on that basis I accept your 100 mile claim, my comment below still stands though.

I'm sure I've said this more than once to a Woosh forum representative, I bet I could flatten the 17 ah battery in just 30 miles, all in pedal assist too, and I'm far from being a weak cyclist.

 

[Julie]

Cheap bike as in the red one you show uses hub gears so a rear hub motor is no good.
Use a GSM mid drive with a KT 17a controller and lcd3.

I was just using the style of frame as an example, i would be using derailleur gears.

I already have a mid drive bike, i want a hub drive.

 

[Julie]

I don't want a road bike with skinny tyres to get the best milage, i have a nice carbon road bike and can't use it now due to arthritic knees, the country lanes i mostly ride on have lots of pot holes, i'm more interested in comfort, i'm currently using a Trek Powerfly 4, i'm getting about 30 miles on Turbo using a 500w battery (2 new batteries, only a couple of months old) That's riding the bike at around 20-22MPH.

Maybe there are people who can get 100 miles from a 17ah battery, i'm not one of them, hence why I know i need 2 batteries, i've ridden the commute about 12 times now, everytime i'm down to less than 20% on my 500w battery doing only 28 relatively flat miles, I"m not fit, and i need a lot of assistance, there are no showers at work, i can't get into work sweaty.

Is there anyway to mount 2 batteries on a small frame (i'm ok with only having one connected). At the moment i'm keeping my spare battery in a pannier, which is working out well, and if that's the way i have to do it i'll go with that, i'm just a bit concerned the weight of the rear hub motor and a battery on the back wheel might be stressful to the rear wheel.

 

[Woosh]

I have, ok one reviewer got a one-off 75 miles and another 79 miles, still 21 and 25 miles shy of your exaggerated claim of 100 miles.

ETA, ah I see they may have been the 13 ah battery. so on that basis I accept your 100 mile claim, my comment below still stands though.

I'm sure I've said this more than once to a Woosh forum representative, I bet I could flatten the 17 ah battery in just 30 miles, all in pedal assist too, and I'm far from being a weak cyclist.

there is no reason for me to argue with your personal experience. I sell bikes to people of all shapes and sizes, each customer has his/her own requirements, there isn't one size fits all solution. As I said, here is the tool to guesstimate what battery capacity you'd need. You can input your weight, bike's weight, frame type, wheel size, tyre type, wind speed, elevation etc. Change the power input to get to your target speed then subtract that required power by how much you want to pedal, then you'll know what battery you need.

 

[Artstu]

Thanks, you were right, there is no way that is going to fit. Do the batteries slide in from the side, not that it would fit this bike, but i'm just wondering what type of frame set up i would need if i buy a suitable bike for conversion.View attachment 26089

I wonder if 37 cm is the longest measurement. so if you angled the corners off to replicate the battery it might actually fit, although chainring clearance and the way the battery latches in would need to be taken into account.