IF Reach - The perfect commuter bike

[eddieo]

I though the Brompton was the perfect commuter bike, this looks a bit heavy to me......

 

[cwah]

Thanks for the explanation guys.

So my only choice is to ask someone to turn back the shoulder on a lathe? Do you know if it's expensive?

D8veh, my bike chainwheel is already 57T so I may not need to change it. I'll have a 13T 1 speed gear + a 57T that should be fine isn't it?

 

[flecc]

Here's a calculator image for the 57/13 tooth combination, showing the cadences at various speeds (click to enlarge):

 

[catsnapper]

'The Cute motor has a removable bush'

Dave, I didn't know that - do you know what width you get with the bush removed?

Alan

 

[jerrysimon]

I find my two speed derailleur Brompton high gear 74" (12T * 54T) about right up to 20mph before I spin out. My Brompton also has a lower gear of 56" (16T * 54T) which I use for starting off. Note this is 16" wheel. With a Tongxin I think you need a minimum of two gears.

My Moulton high gear is lower at 69" and with assist up to 16mph, it spins out a little early but makes me work harder in the process

I guess cwah is much younger than me ? and as such a much higher cadence will be fine for him.

Its going to be a balancing act though if you only have one gear. Too high and it will be a nightmare to start off or if the motor fails. I assume unlike my Tongxins these more powerful rear motors allow you to start off from a standstill ?

Though all that said I really think for these lighter more portable bikes, I much prefer a small light assist front hub motor, after all isn't the point to keep it light enough to carry in an out of shops, supermarkets etc ?

IMHO adding about 3kg+ for a motor and 4kg+ for a battery i.e. 7kg total to the carry weight really seems crazy and pointless. I guess lipos would bring the weight down.

Regards

Jerry

 

[Cyclezee]

Hi Cwah,

If you decide to go with an eZee motor, I agree with D8veh, turning back the 'shoulders' on a lathe by up to 10mm would solve the problem and that would still leave space for a Freewheel, but that is a job for an engineer and one you can trust.
You may be able to stretch the rear forks by a couple of millimeters without too much effort so that the shoulders only needs to be reduced by say 8mm. But as they say in carpentry, measure twice and cut once.

 

[Deleted member 4366]

'The Cute motor has a removable bush'

Dave, I didn't know that - do you know what width you get with the bush removed?

Alan

Here's a photo. It looks about 18-20mm. I'm not at home at the moment, so can't measure it. Because it's removable, it's easy to grind it to any size you want.

 

[cwah]

I though the Brompton was the perfect commuter bike, this looks a bit heavy to me......

Eddio, I said it was the perfect commuter bike because it's small enough to be carried on the bus, tube and groceries but also fast enough to be ridden as a normal bike. This bike doesn't fold as small, but it is WAY FASTER and easier to ride. It is however not as efficient as a normal road bike.

It's quite a nice compromise. I'll see later if I need a smaller bike such as a Brompton for multimodal commuting, but unless I'm travelling in crowded trains/stores, it does his job quite well. (For now without electrification)

This bike is also 11.5 kg. So it's lighter than a Brompton. But it folds indeed bigger.

 

[cwah]

Flecc, I just realised I did a mistake on the chainset turns, it's not 57 but 53T
How do I read your chart? How could I know what is a normal RPM for a human peddling?

Jerry, I'm probably younger than you. I could add multiple speeds on the chainset to be able to start if the motor fails. But it shouldn't happen often so that shoudn't be the main issue. (I hope)

And you're right about the additional weight, I'll probably add 10 kg at the end...

 

[cwah]

Hi Chiwah,

If you decide to go with an eZee motor, I agree with D8veh, turning back the 'shoulders' on a lathe by up to 10mm would solve the problem and that would still leave space for a Freewheel, but that is a job for an engineer and one you can trust.
You may be able to stretch the rear forks by a couple of millimeters without too much effort so that the shoulders only needs to be reduced by say 8mm. But as they say in carpentry, measure twice and cut once.

Thanks, do you have any idea where I could find such as trustful engineer? I think I'll probably need to ask him to make sure the rear magnet can be fixed to the shaft appropriatly:

 

[cwah]

Here's a photo. It looks about 18-20mm. I'm not at home at the moment, so can't measure it. Because it's removable, it's easy to grind it to any size you want.

Dave, do you mean this part is removable?

 

[jerrysimon]

This bike is also 11.5 kg. So it's lighter than a Brompton. But it folds indeed bigger.

The Brompton M3L comes in at 11.5kg as well. Remember too the Brompton has a steel frame. The Ti version (very expensive) is 10.5kg.

I agree though probably rides faster/smoother than the Brompton given its larger 20" wheels and full suspension.

Regards

Jerry

 

[Deleted member 4366]

Dave, do you mean this part is removable?

You've marked the nut. The bush is on the shaft between the nut and the motor. Both can be removed which will shorten the width on that side by about 25mm.

 

[cwah]

Dave, if I get the Cute128 with 145mm dropout and that I remove completely the brush (25 mm), I'll end up with a 120 mm dropout?

I can then just plug a single speed freewheel and that's done?

Jerry, I agree the Brompton seems to be a beautiful bike. I may get one in the future if this bike doesn't fulfil its function

 

[catsnapper]

Thanks for the info Dave, that could be very useful.

Alan

 

[Deleted member 4366]

Dave, if I get the Cute128 with 145mm dropout and that I remove completely the brush (25 mm), I'll end up with a 120 mm dropout?

I can then just plug a single speed freewheel and that's done?

Jerry, I agree the Brompton seems to be a beautiful bike. I may get one in the future if this bike doesn't fulfil its function

Removing the bush might be a good solution ig the q128 has one. Need to study photos. Also, it might make the wheel more central.

 

[flecc]

Flecc, I just realised I did a mistake on the chainset turns, it's not 57 but 53T
How do I read your chart? How could I know what is a normal RPM for a human peddling?

That was only an image of the calculator, here's a new one below that I've copied for the 53/13 tooth combination:



To give an idea of typical cadences (turns per minute), an elderly person cycling to the local shops might well be turning the pedals quite slowly at about 40 to 50 rpm. The average person rides in the 60 to 80 cadence region, while a keen club sport rider or race cyclist typically rides in the 90 to 100 region. Higher cadences are more efficient and less harmful to the knees.

I use a 60 tooth chainwheel on my 20" wheel bike, the size d8veh suggested for you, and with it my top gear is a 13 tooth sprocket so that compares directly with your bike. Below is a second cadence chart for my bike in top gear with 60/13 to give you the cadences you would expect with that combination on your bike:


.

 

[cwah]

Dave, I've found this but I don't think it's really useful.. best to have someone with the Q128:

Thanks Flecc for this explanation. I'm now considering a higher chainwheel. But first I need to sort this rear dropout problem.

 

[Deleted member 4366]

Found all dimensions for Cute motors here:
Motors
It seems to show 145mm between the drop-outs, which is pretty wide, but with a single speed free-wheel you could lose the bush and maybe the nut as well, which would get you close to your 120mm.

 

[cwah]

Thanks Dave. You made me discover the Q-12:

This one seems to fit me better. It's also 135 mm dropout. I probably have to have confirmation from the seller that the bush can be removed.