Can you find the gear reduction ratio of a geared hub motor without opening it up?

[mattjoe49]

Aside from the question in the title, if you just want to hear me vent then then continue reading:

I found the actual motor online from the company (AKM) and looked at their spec sheet and they just don't list poles or magnets or gear reduction ratio.

I have:

• Searched extensively online
• Sent emails in Chinese, French and English to Aikema. Asking them the information I need.
• Reverse image searched to find sellers that rebranded it, hoping they'd list controller configuration information (they didn't)
• Searched in Chinese, Russian, and other languages of countries where Ebikes are popular
• Did however find a Ukrainian seller (Evel.ua) that made a Youtube video where they opened it up. (It's the one on the left) But they do not list the gear reduction ratio either. I also can't say for certain if it's the same motor but it looks identical and has almost the exact same measurements.
• Got a Chinese friend to give me invite access to a Chinese tech forum that you need an invite from some other chinese app to get into it
• Found that it's rebranded by "TopBikeKit", "Yose Power", and "Evel", not sure how many others but they do not list the info needed either
• After reverse image searching further I found a listing on Alibaba and messaged the seller there. No reply.

This has been such a pain in the ass. I'll say that as someone that has built E bikes for many years and loves the hobby, the biggest plague of this hobby is:

1. Proprietary parts where companies have this weird need to put anti tamper stuff all over bikes even though they don't have the infrastructure for having an RMA service or shops. like seriously what the frock is the point in that? i'm not talking about batteries either, that I get. But, I've seen hub motors that have anti tamper screws on them, or the myriad of displays (Which isn't always a good thing) requiring their own manual. Or the amount of times that I've had to take a perfectly good brand new controller and cut off every single connector because they use different connectors. etc
2. The quantity of components that are rebranded or made in house without any sort of spec sheet or anything listed on them.

Thanks for coming to my TED Talk

 

[docw009]

You can put a led across one of the Hall sensor outputs and count the flashes for one full turn when turning the motor backwards. I believe this will give you the magnets x gearing number often used to configure controllers. Then you can count the magnets in the Ukranian video and find the gearing,

Yes, if you have a 9 pin motor connector, it's hard to access the hall lines. I use a cheap motor tester with a 9 pin adapter I made.

 

[mattjoe49]

You can put a led across one of the Hall sensor outputs and count the flashes for one full turn when turning the motor backwards. I believe this will give you the magnets x gearing number often used to configure controllers. Then you can count the magnets in the Ukranian video and find the gearing,

Yes, if you have a 9 pin motor connector, it's hard to access the hall lines. I use a cheap motor tester with a 9 pin adapter I made.

Thank you very much I will be trying this today.

 

[neptronix]

1. Proprietary parts where companies have this weird need to put anti tamper stuff all over bikes even though they don't have the infrastructure for having an RMA service or shops. like seriously what the frock is the point in that? i'm not talking about batteries either, that I get. But, I've seen hub motors that have anti tamper screws on them, or the myriad of displays (Which isn't always a good thing) requiring their own manual. Or the amount of times that I've had to take a perfectly good brand new controller and cut off every single connector because they use different connectors. etc
2. The quantity of components that are rebranded or made in house without any sort of spec sheet or anything listed on them.

This is why i have the rule: no spec? no buy.
If i contact the seller and they don't have the spec, then they don't actually know their product and won't support it well.

This rule will increase your success rate in buying ebike parts massively.

 

[koner]

geared hub motors are usually 1:5 ratio

 

[offGridDownUnder]

geared hub motors are usually 1:5 ratio

Perhaps "or close"?

The ShengYi SX2 is listed as 4.78, although there seems to be some confusion in other sources:
SX1-SX2 - Grin Kits - Product Info

24 Nov 2023 — Axle Length, 100 mm (front) / 136.5mm (rear). Motor Magnetic Pole Pairs, 15 Pole Pair, Outrunner. Gear Ratio, 4.78 : 1 (86T ring, 18T sun).

Gear Ratio: 4.83:1. Magnetic Pole Pairs: 15 (72 effective). Connector: Higo Z910 combined Speedo/Therm. Thermistor: 10K NTC,B3450.

 

[slaphappygamer]

I also have a Shengyi motor (DGW22). Its gear ratio is 5.3:1. Most displays have you round the number, so 5 would be close enough.

 

[mattjoe49]

Thank you all for the replies. I have been unable to continue since I am waiting on a cable to come in. It turns out the motor cable is a proprietary cable and I have to make an adapter before I can begin the LED test that was suggested.

However, I have not given up on finding the motor details and I do have some good news. I believe that I have potentially found the motor rebranded and sold as an SR750D by SuringMax. I cannot stress how much digging it took to find this so if you are here from google, you are welcome.

The looks and dimensions match. Secondly, Ride1up, which my motor belongs to (Cafe Cruiser AKM model) claims that the motor is custom modified by them and is rated for 80n.m of torque and 750W. Well, guess what? The SR750D is 76n.m and 750W.

So, I'm guessing that their motor isn't as exclusive as their marketing claims or maybe there is some backend to the industry that I don't understand.


Either way, Suringmax lists the gear ratio as 1:5:3 in their catalogue PDF but 1:5 on their site. However, KT documentation states to round down so we say 1:5 as others suggested it would be. If my count from the Ukranian video is accurate, then it is 16 magnets.

https://imgur.com/Rh5dItO

If I'm right, this puts the P1 value for a KT controller at 80 unless anything else affects this.

However, I will still be doing a full test to get the value and will update for anyone coming from google.

Edit: Update: The above info is correct, except the P1 value is 85, not 80.