Comment, criticize my build. But be nice I’m new!

[Papa]

To lower the gear ratio implies to have less top speed.
A larger rear sprocket is the correct direction to accomplish that.
Expect more "wheelies".

When a small diameter drive sprocket is feeding a large diameter driven sprocket, chain wrap becomes a concern - this is especially problematic when high wattage motors are used. It is best to avoid exceeding 8:1 ratio when the shafts are close to each other. Beyond this, the practicality of such large ratios can be limited due to power loss and excessive wear on the 9t drive sprocket. If a greater reduction is needed, multiple reduction stages (compound gearing) are suggested. Yes, idler(s) can be employed, but reality is, you shouldn't be running a 9t drive sprocket to begin with... for reasons previously mentioned.

It's the rider's responsibility to reduce "wheelies".

 

[Drubieg]

When a small diameter drive sprocket is feeding a large diameter driven sprocket, chain wrap becomes a concern - this is especially problematic when high wattage motors are used. It is best to avoid exceeding 8:1 ratio when the shafts are close to each other. Beyond this, the practicality of such large ratios can be limited due to power loss and excessive wear on the 9t drive sprocket. If a greater reduction is needed, multiple reduction stages (compound gearing) are suggested. Yes, idler(s) can be employed, but reality is, you shouldn't be running a 9t drive sprocket to begin with... for reasons previously mentioned.

It's the rider's responsibility to reduce "wheelies".

So can you put this in dumb terms for me cus now I’m rather confused. If there is a simple solution that will allow me to use the motor I have, because I likely won’t pay for a new motor, that would be best. do I change the drive sprocket or rear sprocket or both, and if so, what amount of teeth would be recommended? Specifics are helpful

 

[Drubieg]

The small motor sprocket will be loud but because the motor is so fast u really need an even bigger gear ratio. I’d get a different motor with a slower winding. As it is now it’s inefficient and low torque.

Tire Size, RPM, Speed, and Differential Ratio Calculator

Describes the process for converting a gasoline powered car to electric power

www.advanced-ev.com

In an ideal world it would be nice to just “change the motor” but I likely wont pay for that. I can deal with inefficiency as long as the inefficiencies don’t lead to catastrophe. So I’m looking for tips on how to make most of what I already have work. And if something needs to change, I hope I can do it with cheaper, more simple changes.

 

[Papa]

Cars & trucks, for example, use multiple-ratio (staged or compound) transmissions, because the engine's torque curve is narrow over a given RPM range. The transmission's multiple-gears helps to align the engine's optimum torque RPM with the vehicles speed. Some members here have used two sets of chains and/or belts & four sprockets (staged) to accomplish this, while a few others employed vintage 3-speed hubs, with mixed results.

There's a number of previous threads discussing staged/reduction drives throughout this forum. A search would likely prove fruitful.

 

[Hummina Shadeeba]

I had it backwards and a high gear ratio the result is faster and a low ratio would be slower. I think in maybe any other context a “bigger ratio” means a larger difference between the two numbers, which would be slower and more torque.



I can’t think of any simple and cheap changes other than swapping motor to one with lower kv, or lower voltage battery, or maybe higher amp controller or opening the motor and possibly reterminating to wye so lower rpm per volt, or smaller wheel,

 

[Zambam]

How many miles do you have on the bike? Is it meeting your expectations? What do you like/ don't like about it?

How far is your commute?

 

[Drubieg]

How many miles do you have on the bike? Is it meeting your expectations? What do you like/ don't like about it?

How far is your commute?

I have probably 1 mile on it so far lol. I need to install the front brake before I do much more. Thus far tho it rides fine. My commute is not more than 10 miles a day.

 

[99t4]

Anybody have a suggestion for how to lower my gear ratio? Do I simply need a larger front sprocket and smaller rear one?

No, it's the opposite, but you can't realistically go any smaller on the front. In fact, 9t is already suboptimal in terms of chain drive mechanics (reliability, durability, noise, etc.).

 

[Drubieg]

No, it's the opposite, but you can't realistically go any smaller on the front. In fact, 9t is already suboptimal in terms of chain drive mechanics (reliability, durability, noise, etc.)

Thanks, will my setup be catastrophic as it is? Or just shorter life span of chain/sprocket/motor? I imagine I could run it conservatively for a bit until I get something better figured out.

Would increasing the 9t up a few teeth while also increasing the rear sprocket up in teeth be an adequate solution?

 

[Hummina Shadeeba]

Would increasing the 9t up a few teeth while also increasing the rear sprocket up in teeth be an adequate solution?

U want to do the opposite but you probably can’t get a smaller sprocket on the front or bigger on the back

 

[Drubieg]

Cars & trucks, for example, use multiple-ratio (staged or compound) transmissions, because the engine's torque curve is narrow over a given RPM range. The transmission's multiple-gears helps to align the engine's optimum torque RPM with the vehicles speed. Some members here have used two sets of chains and/or belts & four sprockets (staged) to accomplish this, while a few others employed vintage 3-speed hubs, with mixed results.

There's a number of previous threads discussing staged/reduction drives throughout this forum. A search would likely prove fruitful.

Thanks I’ll have to look deeper I guess. I’ve done some digging and all I come up with is a bunch of non specific theory.

 

[Drubieg]

U want to do the opposite but you probably can’t get a smaller sprocket on the front or bigger on the back

Ooo ok wow, yea I see how smaller in front is a no go. The rear is maybe still a possibility tho. Otherwise seems I’ll have to add a third or fourth sprocket with another chain

 

[BionicOnion]

Ooo ok wow, yea I see how smaller in front is a no go. The rear is maybe still a possibility tho. Otherwise seems I’ll have to add a third or fourth sprocket with another chain

Sounds like they are suggesting a jack shaft idea, take the motor to a medium shaft with say a 12/24 sprockets to reduce speed then you can use a different sprocket off the same shaft to drive the wheel. Yeah it's gonna affect range and noise a bit, but it enables more reasonable ratios because they would multiple together

 

[PaPaSteve]

What size chain ?
Here is an example image for a method to increase chain wrap on the smaller sprocket.
This image shows a rubbing block but a idler sprocket with bearing would be better.
A bigger rear sprocket with the correct bolt pattern to fit your hub may need to be custom made.
It's possible buy a sprocket "blank" then use the existing sprocket as a drilling template to make your own.

Blank Sprockets » Product categories » Azusaparts

 

[bengxe]

Yea, I’m realizing my brake choice isn’t the best but I’m not sure I can even mount disc brakes with my setup. I’ll look more into it I guess.

I've seen adapters to put u-brakes like you have in the rear in place of the side pull you'd have to use on that fork. That seems like it'd be an improvement.
#35 sprockets exist up to at least 85t, if you can tolerate the noise and chain wear from the 9t you might be able to make your single stage work. I think I would
I'd think you also need to find a way to stop over drawing your batteries. If that controller isn't programmable you could use a cycle analyst to limit the current, or maybe add another parallel group on the front of the handle bars.

 

[Hummina Shadeeba]

I’d get a chain with a smaller distance between pins so can get a higher (?) gear ratio. the diameter of the sprockets determine the ratio but everything shrinks and more teeth on back for same diameter



I wouldn’t go bigger than an 8-speed chain and maybe even smaller would be worth it. They’re cheap so just replace it as it stretches and doubt you’d ever break it.

 

[Drubieg]

What size chain ?
Here is an example image for a method to increase chain wrap on the smaller sprocket.
This image shows a rubbing block but a idler sprocket with bearing would be better.
A bigger rear sprocket with the correct bolt pattern to fit your hub may need to be custom made.
It's possible buy a sprocket "blank" then use the existing sprocket as a drilling template to make your own.

Blank Sprockets » Product categories » Azusaparts

Thanks so much, it’s a 35 chain

 

[Drubieg]

I've seen adapters to put u-brakes like you have in the rear in place of the side pull you'd have to use on that fork. That seems like it'd be an improvement.
#35 sprockets exist up to at least 85t, if you can tolerate the noise and chain wear from the 9t you might be able to make your single stage work. I think I would
I'd think you also need to find a way to stop over drawing your batteries. If that controller isn't programmable you could use a cycle analyst to limit the current, or maybe add another parallel group on the front of the handle bars.

Thanks for addressing my other question about battery draw. This is helpful

 

[Drubieg]

I’d get a chain with a smaller distance between pins so can get a higher (?) gear ratio without needing to get a physically larger rear cog. You don’t need a beefy #35 chain especially as you’re “spinning” not “mashing”.

Itll be a bit more time tensioning and maintaining but worth it.

I wouldn’t go bigger than an 8-speed chain and maybe even smaller would be worth it. They’re cheap so just replace it as it stretches and doubt you’d ever break it.

I didn’t realize chain size would affect the gear ratio… that’s useful

 

[offGridDownUnder]

You are going to discover the drawbacks by riding it. The comments are also helpful, but won't be enough by themselves - the reality will sharpen your understanding. So, good so far, and hope nothing catastrophic happens while you're learning more.

Can you split the battery pack into two "saddle bags" to move them lower and more forward for balance?

 

[offGridDownUnder]

I didn’t realize chain size would affect the gear ratio

?

It will not. The ratio will be determined entirely by the size of the input sprocket (pulley) diameter and the output sprocket (pulley) diameter.

It may be true that a shorter chain link would permit a smaller diameter due to the mechanics of cutting sprockets, and that this then permits a different ratio, but apart from that, the chain pitch has no input

 

[Drubieg]

You are going to discover the drawbacks by riding it. The comments are also helpful, but won't be enough by themselves - the reality will sharpen your understanding. So, good so far, and hope nothing catastrophic happens while you're learning more.

Can you split the battery pack into two "saddle bags" to move them lower and more forward for balance?

Yea that seems like a change I could make easily. Ur right on the learning through experience, I figured as much

 

[Hummina Shadeeba]

I didn’t realize chain size would affect the gear ratio… that’s useful

Of course the chain size doesn’t directly affect the ratio but enables a bigger size difference between the sprockets which is what you need. You can get a lot more teeth on the rear for the same diameter and on the front you could keep the same amount of teeth or leave it the same diameter, having more teeth, which wouldn’t help the ratio but has benefits listed above

 

[Zambam]

Can you split the battery pack into two "saddle bags" to move them lower and more forward for balance?

Since it cannot have pedals, How about split the battery packs and mount them as platform foot pegs? That'll lower C.G. with improved handling.

 

[Papa]

Here's your current ratio (based on estimated loaded RPM):



And a 'ballpark' estimate what it likely should be for single stage reduction:



Ratio 14 to 1. (which requires a driven sprocket of 126 teeth.