Please advise on best toque arm options please...

[anotherkiwi]

I've never seen an 8-speed freewheel on a motor at 135mm wide. That's not to say that there isn't one, though. Personally, I'll believe it when I've seen it.
7 speed is 135mm. The stack-height of an 8-speed is only a few mm more, but it overlap the axle nut, so it would lock against the frame. You therefore need to add a spacer onto the axle, which is basically a thick washer with 20mm O/D and 12m hole. That's a non-standard size. You can get them, but they take some hunting around to find.

Those few mm don't make much difference to the width, but it's all on one side and the wrong side because that side is already longer than the other, which means that you have to put a bigger dish in the wheel to get the rim central. The wheel won't be built like that, so you have to do it yourself, which requires a bit of skill and experience.

When you put a dish in the wheel, the spoke tension is different from one side to the other. A small dish is no problem, but as you go further, the difference goes up exponentially until you have zero tension on one side and astronomic tension on the other when the spokes on one side are perpendicular to the hub. Obviously, you can't dish any further than that. The dish you need for an 8 speed is in the area where the difference in tension is too much.

You can solve the dish problem by adding spacers to the left side in order to bring the rim in the centre, but that increases your overall width.. That's OK on an aluminium frame because you can stretch it. I've taken a 135mm frame to 150mm, but you can't stretch carbon fibre.

I know some people are quite happy running around with 8 speed freewheels and their rim off centre. It can be a problem with rim brakes, though you can pay around with the spacers to mitigate it.

That answers quite a few of my own questions, thanks.

From what I know an 8 speed freewheel (DNP) will require about 142 mm dropouts - 135 mm hub + 2 x 3 mm thick washers to keep the hub centered, one on each side.

So far I have been unable to convince them that there is a market for a wide range 7 speed freewheel. Maybe they are right, there isn't one...

 

[Brummie]

That answers quite a few of my own questions, thanks.

From what I know an 8 speed freewheel (DNP) will require about 142 mm dropouts - 135 mm hub + 2 x 3 mm thick washers to keep the hub centered, one on each side.

So far I have been unable to convince them that there is a market for a wide range 7 speed freewheel. Maybe they are right, there isn't one...

Who have you been unable to convince?

There must be a market for wide range 7-8 speed conversions with 135 dropouts because the majority of new donor MTB/hybrids are 7-8 spd with 135 dropouts. Unfortunately Freehub conversions are often considered an upgrade to a freewheel standard (that new bikes aren't fitted with).

 

[Brummie]

I've never seen an 8-speed freewheel on a motor at 135mm wide. That's not to say that there isn't one, though. Personally, I'll believe it when I've seen it.
7 speed is 135mm. The stack-height of an 8-speed is only a few mm more, but it overlap the axle nut, so it would lock against the frame. You therefore need to add a spacer onto the axle, which is basically a thick washer with 20mm O/D and 12m hole. That's a non-standard size. You can get them, but they take some hunting around to find.

Those few mm don't make much difference to the width, but it's all on one side and the wrong side because that side is already longer than the other, which means that you have to put a bigger dish in the wheel to get the rim central. The wheel won't be built like that, so you have to do it yourself, which requires a bit of skill and experience.

When you put a dish in the wheel, the spoke tension is different from one side to the other. A small dish is no problem, but as you go further, the difference goes up exponentially until you have zero tension on one side and astronomic tension on the other when the spokes on one side are perpendicular to the hub. Obviously, you can't dish any further than that. The dish you need for an 8 speed is in the area where the difference in tension is too much.

You can solve the dish problem by adding spacers to the left side in order to bring the rim in the centre, but that increases your overall width.. That's OK on an aluminium frame because you can stretch it. I've taken a 135mm frame to 150mm, but you can't stretch carbon fibre.

I know some people are quite happy running around with 8 speed freewheels and their rim off centre. It can be a problem with rim brakes, though you can pay around with the spacers to mitigate it.

Thanks. That was most informative. I appreciate the effort in your explanation.
Fortunately I have a supply of such washers but are you sure they don't need to be 14mm?
My dropouts appear very easy to widen so I just tried my existing wheel with 10mm washers (2 x 3mm) on one side & then both sides (147mm total). Fortunately my mechanical disc brake was originally at the extreme end of the adjustment and after creating the wheel offset (washers on gear side) it just puts the slotted brake adjustment to the other end, so all looks good (maybe more luck than anything)!

 

[Deleted member 4366]

You can realign the brake caliper to the disc by putting washers behind the caliper mount. If you can spring the frame, it's no problem then.

 

[Woosh]

I've never seen an 8-speed freewheel on a motor at 135mm wide. That's not to say that there isn't one, though. Personally, I'll believe it when I've seen it.
7 speed is 135mm. The stack-height of an 8-speed is only a few mm more, but it overlap the axle nut, so it would lock against the frame.

I use a lot of DNP 8-speed screw-on freewheels, and to me, there isn't a problem. let's discuss this rationally.
The standard width of a cassette or freewheel is 39mm.
When you buy a Sunrace or DNP 'shimano compatible' freewheel, you get just that, an 8-speed, 9-speed or 10-speed freewheel that has the same 39mm width and cog to cog spacing as a Shimano cassette with the same number of speed.
There is no need to add spacers to your motor's axle and no need to re-dish your rear motor wheel.
This is the proof (I took the picture and the measurements myself): There is no difference in width (same 39mm) between a DNP-8-speed freewheel on the left and a Shimano CS-HG41-8 8-speed cassette on the right.

and this is a 10-speed Sunrace freewheel, same 39mm width.
https://www.sjscycles.co.uk/freewheels/sunrace-10-speed-freewheel-1136t/

This is what you are supposed to keep to:

 

[anotherkiwi]

37 mm from the motor body to the axle nut on the motor and 40 mm stack height for the DNP Epoch 11-32 (or 11-34) 8 speed means it will need a 3.5 mm washer to stop it rubbing on the frame. In order to keep the wheel centered for the rim brakes you need to add another washer to the non drive side.

Who have you been unable to convince?

DNP, I ordered my freewheel direct from them. Very nice helpful people who made me a cassette to special order for another idea I had.

Next step is to buy a selection of different freewheels and take them to bits to make my own Franken-freewheel. <nefarious cackle>...

 

[Brummie]

Thanks kiwi and understood. You have 37mm to fit a 40mm freewheel or cassette unless they've narrowed the motor or you stretch the stays to squeeze a washer into to avoid the potential small cog foul issue.
There could be a increase in the market for these old freewheel gears at 7spd+ as a result of eConversion kits being used on bikes that originally have 7spd+ freehubs because freewheels appear to be more common on eKits.

 

[anotherkiwi]

My dream freewheel is a 13-40 7 speed but I could live with a 13-34. Using a 36-58 chainwheel gives a spin out speed of around 60 km/h in top gear which in my experience is plenty. The motor gives assistance to 27 km/h or so means being in 36:18 at cadence or 58:28, I am quite happy with those ratios.

What I am thinking:

- tiny xiongda with 10 A KT controller (20 A controller but used in assistance level 4 of 5) and a 12S 44.4v battery so about 498 W peak hot off the charger
- Patterson Metropolis drive in place of normal chainwheel
- this combination adds just over 3 kg to my trike without the battery (you take the battery off to fold the trike and lift it...) so 20-22 kg total to manhandle.

What happens when your finger slips and you feed 20 A to that tiny little motor?

 

[Woosh]

What happens when your finger slips and you feed 20 A to that tiny little motor?

it can't be good.
I reckon it would be magnetically saturated at around 15A. Anything over would be turned to heat.

 

[anotherkiwi]

As long as it doesn't go pop before you realise...

 

[Woosh]

As long as it doesn't go pop before you realise...

KT sell a 8A-16A controller (16S). I have Lishui 7A-15A controllers in stock.

 

[Brummie]

There are plenty of 34T versions on ebay but 40T is large!
I found a performance table for that motor previously (can't find it now) and it showed that it's power plateaued out at just under 11A/400W (from memory). I'm not sure if I would draw more current if your controller permitted but the efficiency curves dropped off and gave no more power output.

 

[Woosh]

11A is too low for the average e-cyclist.
The Aikema 100SX saturates at around 17A/40NM and weighs 2.1kg.

http://www.aikema.com.cn/En_ArticleShow.asp?ArticleID=292

 

[Brummie]

It was a chart like this one that I saw. Stolen from d8veh on another thread...