What should my final gear ratio be?

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My kart is probably going to be around 150lbs, with occasionally over 300lbs rider and tow (I'm gonna hook up a bike trailer to tow my kids in), 3800rpm max, and 16" tires. I have 6:1 but after reading a bit more that seems like it's not enough. I can find 80T sprockets giving me 8:1, but they're about $80 or more. Would it be better to do the extra work and install a reducer of some sort, or make my own reduction with a live axle or such to get a better ratio? I could also get a 9T or 8T drive sprocket, but someone told me that few of teeth could be hard on the chain. What's my best bet?
 

KMEFA

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What motor are you using, & what size chain ??

Is it the converted alternator ?

I run ''good quality'' #35 chain on all my stuff, ''gas & elect''.

The biggest motor sprockets avail. ''that will go right on'' - MY 1020 & BM 1109 motors for # 35 chain ,, is a double 'D'' 10t.

I did incorporate a finish bore #35 sprocket on a brushed MY1020 elect. motor awhile back,, as I went to 11t.
Had to machine a step bushing though.

Live axel & split sprocket set up ect. ,, is the way I would go,, If you can swing it,, as you can do ''quick'' - inexpensive - sprocket/gear changes .
Probably cost ''way'' more than the 80 bucks for an 80t sprocket that you are lookin at though....

Am thinking your 8 - 1 figure for heavy weight, towing,, & efficiency ,,, would definitely be the way to go,,,, if running any of these motors. ;)


Don't think it will be fast,, but should more than likely pull ok.

I
 
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Messages
73
Reaction score
5
Location
Albany, OR
What motor are you using, & what size chain ??

Is it the converted alternator ?

I run ''good quality'' #35 chain on all my stuff, ''gas & elect''.

The biggest motor sprockets avail. ''that will go right on'' - MY 1020 & BM 1109 motors for # 35 chain ,, is a double 'D'' 10t.

I did incorporate a finish bore #35 sprocket on a brushed MY1020 elect. motor awhile back,, as I went to 11t.
Had to machine a step bushing though.

Live axel & split sprocket set up ect. ,, is the way I would go,, If you can swing it,, as you can do ''quick'' - inexpensive - sprocket/gear changes .
Probably cost ''way'' more than the 80 bucks for an 80t sprocket that you are lookin at though....

Am thinking your 8 - 1 figure for heavy weight, towing,, & efficiency ,,, would definitely be the way to go,,,, if running any of these motors. ;)


Don't think it will be fast,, but should more than likely pull ok.

I
Yes, it's the converted alternator. I *have* #40 chain but it's still returnable to Amazon. I don't have any obligations right now. I have a 36-tooth #40 sprocket, but I'm not committed to it. I'll use whatever seems to be the best option for my situation, which I still don't know what that is.

Sidenote: I just got someone to machine the shaft down to 5/8 so at least I have a lot more options now. Looks like #35 chain is gonna be a my best option. I can get a 10T drive sprocket and 94T axle sprocket for a good bit less money.

EDIT: I bought 10T and 94T #35. This also gives me the advantage of reducing max speed to under 20mph, which gives me a lot more leeway where I live, and it's plenty far enough for me and kids.
 
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KMEFA

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94 /10 - 9.4 - 1 ratio,, ought to just about make it into a stump puller ! LOL :p

That's a ''huge'' final sprocket !

Are you going to be ok for ground clearance with that ??
 
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94 /10 - 9.4 - 1 ratio,, ought to just about make that into a stump puller ! LOL :p

That's a ''huge'' final sprocket !

Are you going to be ok for ground clearance with that ??
Barely, but yes. That will give it a max speed of like 19mph, maybe less.

Edit: sprocket vs my 16" wheels
16106563547976879180323606018813.jpg
 

KMEFA

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Should be fairly quick, when not towing ect.
You might want to think about some kind of deflector/ skid plate mounted to the frame or something ahead of the sprocket, if you don't have something already . ;)
 
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Should be fairly quick, when not towing ect.
You might want to think about some kind of deflector/ skid plate mounted to the frame or something ahead of the sprocket, if you don't have something already . ;)
Yeah, I have some angle iron and 16 guage plate I'm going to turn into a cover. Might buy some 22 guage sheet, since it's not very expensive at Home Depot

94 /10 - 9.4 - 1 ratio,, ought to just about make it into a stump puller ! LOL :p

That's a ''huge'' final sprocket !

Are you going to be ok for ground clearance with that ??
Yeah kinda. The kart plus me is over 300 lbs, and I want to also be able to tow my kids in a little bike trailer. But I do have 16" wheels as I mentioned, so it'll still be fairly speedy.
 

ShadowNightmares

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Yes, it's the converted alternator. I *have* #40 chain but it's still returnable to Amazon. I don't have any obligations right now. I have a 36-tooth #40 sprocket, but I'm not committed to it. I'll use whatever seems to be the best option for my situation, which I still don't know what that is.

Sidenote: I just got someone to machine the shaft down to 5/8 so at least I have a lot more options now. Looks like #35 chain is gonna be a my best option. I can get a 10T drive sprocket and 94T axle sprocket for a good bit less money.

EDIT: I bought 10T and 94T #35. This also gives me the advantage of reducing max speed to under 20mph, which gives me a lot more leeway where I live, and it's plenty far enough for me and kids.
Hey, nice to meet someone else that wants to use a converted alternator.
I would sincerely recommend you to check out these videos and think about installing hall sensors on your alternator
(from YT/Enrengineering)
(from YT/Electrojuanyu)
(from YT/Austiwawa)
Sensored BLDC motors can offer more torque at low speeds, and will help to avoid "cogging" while it tries to synchronize
 
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Albany, OR
Hey, nice to meet someone else that wants to use a converted alternator.
I would sincerely recommend you to check out these videos and think about installing hall sensors on your alternator
(from YT/Enrengineering)
(from YT/Electrojuanyu)
(from YT/Austiwawa)
Sensored BLDC motors can offer more torque at low speeds, and will help to avoid "cogging" while it tries to synchronize
This was honestly not an idea I had considered. It even looks fairly simple/easy to do, and I think the controller I have supports both types.
 
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