Sunstar SO3 opinions

Thinking of buying a Sunstar SO3, 250w 36v mid drive motor. They look well built. Leaving the price out of the equation what do people think of them?

I'm aware that they've ceased production & future service may be difficult.

It'll be going on a recumbent trike with a Rohloff IGH which I'll be be keeping. I need a torque sensor due to a physical issue with synchronising hands & feet. I definitely don't want a throttle and the Rohloff means I can't have a hub motor. The trike weighs 30kg and I tour with a trailer with 30kg in it plus me at 80kg so a heavy load plus it needs to go up steep hills.

The only other candidate is the Tongshen TSDZ2 but a few things put me off, plastic gears, a maximum chainring of 42T as larger ones can damage the motor plus build quality is not as good as the metal geared, built in Japan, Sunstar.

I guess the question has to be: Is the Sunstar up to the usage and what other alternatives are there?

All three versions, SO1, SO2 and SO3 have been rather low powered, rather like the original Panasonic motor but very much noisier despite both using steel gears. As a result they were never popular, leading to them stopping production.

I don't think the SO3 is at all suitable for your load pulling needs, just too low powered for the job.

I don't have personal knowledge of today's crank drive kit alternatives but I know they are all more powerful and better suited. Hopefully owners will come in with suggestions. Don't worry about having nylon gears, they are usually up to the job and run far more silently.

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Thanks flecc. afaik they stopped production as most motors were being built into bikes, the retrofit market is small and they couldn't compete with chinese units. Sunstars main business is motorcycle gears so I think that they couldn't be bothered making a niche (for them) product.

Are they underpowered compared to the Tongsheng? I know of someone using one on a cargo bike. I understand that originally they were 24v but are now 36v.

The only other candidate is the Tongshen TSDZ2 but a few things put me off, plastic gears, a maximum chainring of 42T as larger ones can damage the motor plus build quality is not as good as the metal geared, built in Japan, Sunstar.

the plastic in the blue transfer gear is there to give a degree of stress absorption.

You can buy replacement part on ebay and it's easy to refit.

There are metal versions but you would move the stress to the motor spindle. The rest of the gearbox is made of steel.

I only knew the 24 volt one, the later option of 36 volt batteries would have increased the motor revs by 50% which if the bike was suitably geared down to the same speed would give more power. Its motor is quite small though, so will have some limitations.

I'd still be very hesitant about using it to climb steep hills with 140 kilos all in and the rolling resistance of five tyres. That's a high demand for any e-bike motor.

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the plastic in the blue transfer gear is there to give a degree of stress absorption.

You can buy replacement part on ebay and it's easy to refit.

There are metal versions but you would move the stress to the motor spindle. The rest of the gearbox is made of steel.

Ah that explains the plastic. I guess on a long european tour it's best to carry a spare.

It'll be going on a 20in trike so does the 42T chainring rule still hold? Compared to a 26in wheel I "lose" 23 gear inches (with a 17T single rear sprocket on the Rohloff) which makes the top gear too low and spinning out at a low speed. Can I put a 50/34 double on it?

Would you consider it man enough for the usage above? I'll have a very low gear on the setup, eg most mtb's have a low of 16gi, I'll have 11gi that's about 3 gears lower. Also on a recumbent trike you can't stand up and stomp on the pedals so little in the way of shock loading.

Ah that explains the plastic. I guess on a long european tour it's best to carry a spare.

It'll be going on a 20in trike so does the 42T chainring rule still hold? Compared to a 26in wheel I "lose" 23 gear inches (with a 17T single rear sprocket on the Rohloff) which makes the top gear too low and spinning out at a low speed. Can I put a 50/34 double on it?

Would you consider it man enough for the usage above? I'll have a very low gear on the setup, eg most mtb's have a low of 16gi, I'll have 11gi that's about 3 gears lower. Also on a recumbent trike you can't stand up and stomp on the pedals so little in the way of shock loading.

With that load you could try 46/30 or 48/32. I can't spin out on my 26" trike with a 48:11 top gear so I am going to mount a 48/32 double on my GSM motor.

Not surprised you're not spinning out as that's 111gi!

Smallest chainring on a 110BCD is 34T. With a 17T rear sprocket on the Rohloff that makes 11.16gi lowest. Putting a 50t and the 17t makes 86gi top. Sure, I'll spin out around 20mph but that's high enough with a load for me. I have choice of 13 to 21t sprockets so can tweak those numbers but I'd like to have a super low gear for when the battery runs out.

from memory, the GSM and Bafang BBS01 have a spindle about 12mm in diameter, the Tongsheng spindle is about 10mm in diameter, it looks more fragile in any case in comparison. The other difference is that the Tongsheng spins at 4,000 RPM max, the GSM and BBS01 spins at 2000RPM.

That's why I am worried about breaking the Tongsheng spindle.

from memory, the GSM and Bafang BBS01 have a spindle about 12mm in diameter, the Tongsheng spindle is about 10mm in diameter, it looks more fragile in any case in comparison. The other difference is that the Tongsheng spins at 4,000 RPM max, the GSM and BBS01 spins at 2000RPM.

That's why I am worried about breaking the Tongsheng spindle.

Are you saying don't use a larger chainring than 42t? Would the spindle size affect the choice of low gears?

Are you saying don't use a larger chainring than 42t? Would the spindle size affect the choice of low gears?

A bigger ring means more stress.

in a year time, I should be able to answer that question with confidence. It's still early days for us regarding the TSDZ2. Nothing has been reported broken, I have asked Tongsheng to push the motor as far as they are confident, they already warned me that pushing it further will cause early damage to the blue gear.

Please don't shoot the messenger!

Not surprised you're not spinning out as that's 111gi!

114.5 gi to be exact with the Big Ben tyre. We have very steep hills but I am no longer strong enough... Spinning out at 40 km/h is just a little slow for me about 50-55 km/h is more my sweet spot, above that I hunker down and hang on tight. I have 26:40 low gear at the moment which works most places without as much load as you are pulling. I looked at really low ratios but decided that eliminating the empty battery factor was easier SWMBO says I can't buy a decent trailer I have to go shopping with her car

Smallest chainring on a 110BCD is 34T. With a 17T rear sprocket on the Rohloff that makes 11.16gi lowest. Putting a 50t and the 17t makes 86gi top. Sure, I'll spin out around 20mph but that's high enough with a load for me. I have choice of 13 to 21t sprockets so can tweak those numbers but I'd like to have a super low gear for when the battery runs out.

https://www.amazon.com/Exclusive-Customized-Chainring-TONGSHENG-Conversion/dp/B071LD2C9K

A bigger ring means more stress.

in a year time, I should be able to answer that question with confidence. It's still early days for us regarding the TSDZ2. Nothing has been reported broken, I have asked Tongsheng to push the motor as far as they are confident, they already warned me that pushing it further will cause early damage to the blue gear.

Please don't shoot the messenger!

You're right of course but's relative to wheel size. I would think that Tongsheng figures are for a 26" (or similar) wheel which using 42t front and 11 rear you get 97 gear inches, same gears on my 20" wheel get 81gi. If Tongsheng are happy at 97gi then there's no reason I can't use a 50t which gets me 86gi.

Hope that makes sense.

But I use a 17t rear sprocket on a rohloff which complicates things a bit so i've referenced the calcs below and done screen shots

Here's how:

The online derailleur calculator is:

http://www.bikecalc.com/gear_inches

Put in

26" wheel

Front cog 42

rear cog . 11

results are 97gi

now go to

http://schlumpf.ch/hp/berechnungen/engl_berechnen_nabenschaltung_inch.htm

which is a calculator for hub gears

circumference 1.59 (20" x 1.75)

front 42

rear 17 (which I have fitted)

Scroll down to the Rohloff results at the bottom, Column 1:1 (ignore the other columns as they relate to other gear systems)

result is 72gi

now change the front cog to 50 and results are 86gi, well below the 97gi above

Phew! Gave me a headache too!

So you see where I'm coming from. imo it can't be stressing the motor.

26" wheel derailleur 42/11 highest gear

20" Rohloff hub gear 42/17

20" Rohloff hub gear 50/17

You're right of course but's relative to wheel size. I would think that Tongsheng figures are for a 26" (or similar) wheel which using 42t front and 11 rear you get 97 gear inches, same gears on my 20" wheel get 81gi. If Tongsheng are happy at 97gi then there's no reason I can't use a 50t which gets me 86gi.

Hope that makes sense.

But I use a 17t rear sprocket on a rohloff which complicates things a bit so i've referenced the calcs below and done screen shots

 

Here's how:

The online derailleur calculator is:

http://www.bikecalc.com/gear_inches

Put in

26" wheel

Front cog 42

rear cog . 11

 

results are 97gi

 

now go to

http://schlumpf.ch/hp/berechnungen/engl_berechnen_nabenschaltung_inch.htm

which is a calculator for hub gears

 

circumference 1.59 (20" x 1.75)

front 42

rear 17 (which I have fitted)

Scroll down to the Rohloff results at the bottom, Column 1:1 (ignore the other columns as they relate to other gear systems)

result is 72gi

 

now change the front cog to 50 and results are 86gi, well below the 97gi above

 

Phew! Gave me a headache too!

 

So you see where I'm coming from. imo it can't be stressing the motor.

 

26" wheel derailleur 42/11 highest gear

[ATTACH=full]28310[/ATTACH]

 

20" Rohloff hub gear 42/17

[ATTACH=full]28309[/ATTACH]

 

20" Rohloff hub gear 50/17

[ATTACH=full]28308[/ATTACH]

Your calculations are correct with respect to preserving the motor. With the load you are pulling I would go for a 48 or a 46 tooth big chainwheel keeping the 34 small one. At a few quid a pop you could buy a couple of different sizes and do real world tests.

Apart from the Tongsheng what other drives are there that are both torque sensing and take a double chainring

There are some Bafang ones, you would have to make an adaptor or have the motor bracket welded to a boom.

https://www.bafang-e.com/en/components/component/motor/mm-g332250.html

Hi Climo,

You are right, sorry for the delay in responding. I was travelling yesterday.

You should also take the average load of 100kgs into consideration, more load, less speed.

I agree with anotherkiwi when he said you could buy a couple of different sizes and do the real world test.

That's a relief, Whoosh & Kiwi. I was doubting my reasoning (and my sanity). If I keep the max gi below 95 then I'll be ok then it puts the Tongsheng back in the running.

On the flat with that load I'm using the top 3 gears on a 50/17 without a motor at about 13-14mph which isn't bad for an old fart. Hills are a struggle & that's what the low gearing and the motor's for.

I may have used top gear (48:11) 3 or 4 times since I got the trike... On the flat and slight downhills I spend most of my time in 48:15 at about 40 km/h. Last season on my flat 27 km training route I got fit enough for about 32 km/h average. That is me and an "empty" trike, just the two small paniers with my gear.

Now I need a motor to get out of the house! First incline is there just in front of me as I type and over 13%, with cold muscles... 15% on the way home Unrestricted the motor will provide 50 km/h cruising speed on the flat

Your calculations are correct with respect to preserving the motor. With the load you are pulling I would go for a 48 or a 46 tooth big chainwheel keeping the 34 small one. At a few quid a pop you could buy a couple of different sizes and do real world tests.

You're right and experiment with different chainrings.

Using the motor on low setting how many gears do you increase when using the same rider input. What I mean is, if in a given situation you were in gear 6 are you now in gear 8? Conversely when the motor is off how much resistance are you getting, again in gear usage? Knowing that would help me select a gear to exploit gear 11 in the rohloff which is the most efficient gear. Hope that's clear.

Does a regular front derailleur position work or does the motor push the chainset position out further to the right? ie do I need to mount the FD on an additional bracket so it sits in the correct position above the chainset?

Whoosh, I'd be buying from you - how reliable is the Tongsheng unit? I'm planning a 2000km tour in Europe next year so would take a spare blue gear plus any other spares you recommend. If the motor or other bit failed on tour would you UPS another to me - obviously at my expense.

I may have used top gear (48:11) 3 or 4 times since I got the trike... On the flat and slight downhills I spend most of my time in 48:15 at about 40 km/h. Last season on my flat 27 km training route I got fit enough for about 32 km/h average. That is me and an "empty" trike, just the two small paniers with my gear.

 

Now I need a motor to get out of the house! First incline is there just in front of me as I type and over 13%, with cold muscles... 15% on the way home Unrestricted the motor will provide 50 km/h cruising speed on the flat

I'm seriously impressed at your speeds. 26" trikes are faster than 20" and your Azub is lighter than my HP Velotechnik but that's still very impressive. Sounds like, with a motor, you should get a 60t

I know that 48v is more powerful than 36v, though no idea why (I'm no electrician). What effect does that have on the battery range - does it do less miles for a given Ah battery?

How many hours does a battery take to charge?

The energy in a battery is measured in watt hours (wh), which are a multiple of volts (v) and amp house (Ah). So a 48v 10Ah battery is 480wh, and a 36v 10Ah battery just 360wh. Some battery makers (eg Bosch) mark wh as their main published measure.

So if you use the same effective power a 48v battery will give more miles than a 36v one of same aH, pretty much in proportion 48/36 or 4/3, or extra 33%. If you take advantage of the 48v to squeeze maximum power from the motor you will get through the available energy quicker. You will probably still get more miles from the 48v, but not as much as 33% more.

The energy in a battery is measured in watt hours (wh), which are a multiple of volts (v) and amp house (Ah). So a 48v 10Ah battery is 480wh, and a 36v 10Ah battery just 360wh. Some battery makers (eg Bosch) mark wh as their main published measure.

 

So if you use the same effective power a 48v battery will give more miles than a 36v one of same aH, pretty much in proportion 48/36 or 4/3, or extra 33%. If you take advantage of the 48v to squeeze maximum power from the motor you will get through the available energy quicker. You will probably still get more miles from the 48v, but not as much as 33% more.

Thanks for the succinct explanation. I'll almost certainly leave the Tongsheng as is and therefore effectively have a larger battery.

You're right and experiment with different chainrings.

Using the motor on low setting how many gears do you increase when using the same rider input. What I mean is, if in a given situation you were in gear 6 are you now in gear 8? Conversely when the motor is off how much resistance are you getting, again in gear usage? Knowing that would help me select a gear to exploit gear 11 in the rohloff which is the most efficient gear. Hope that's clear.

Does a regular front derailleur position work or does the motor push the chainset position out further to the right? ie do I need to mount the FD on an additional bracket so it sits in the correct position above the chainset?

 

Whoosh, I'd be buying from you - how reliable is the Tongsheng unit? I'm planning a 2000km tour in Europe next year so would take a spare blue gear plus any other spares you recommend. If the motor or other bit failed on tour would you UPS another to me - obviously at my expense.

For the moment my motor is on an upright with 28" wheels.

I would say that on the flat the motor is equivalent to 2 or 3 gears increase - I do ride on the flat without the motor switched on and battery not on the bike from time to time. So on the 8 speed cassette instead of using 3rd gear I would be using 5th on the flat and 6th as soon as there is a gradient. I am much more efficient on the trike so am expecting to have a 3 gear difference. That is up to 25 km/h so the motor will only be used for stop and go traffic and climbing hills. On the upright I am much faster than most cars from 0 to 30 km/h away from the lights and on the flat riding with some effort is about 32 km/h top speed.

You might need to move the derailleur out, with the GSM I will need to move out about 20 mm maybe a bit more. I am going to make an extension piece in CF and use a Sora or equivalent 2 speed derailleur with 16 tooth difference and 48-32 tooth chainwheels. Before I get there I will run the motor with the single 46 tooth standard chainwheel. The drivechain will also be converted to 10 speed and an 11-42 or 11-46 cassette mounted.