What should my final gear ratio be?

Messages
72
Reaction score
4
Location
Albany, OR
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?
 

I74

Active member
Messages
211
Reaction score
67
Location
Cedar Rapids IA
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
 
Last edited:
Messages
72
Reaction score
4
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.
 
Last edited:

I74

Active member
Messages
211
Reaction score
67
Location
Cedar Rapids IA
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 ??
 
Messages
72
Reaction score
4
Location
Albany, OR
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
 

I74

Active member
Messages
211
Reaction score
67
Location
Cedar Rapids IA
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 . ;)
 
Messages
72
Reaction score
4
Location
Albany, OR
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.
 
  • Like
Reactions: I74

ShadowNightmares

New member
Messages
15
Reaction score
1
Location
Goiania, Goias, Brazil
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
 
Messages
72
Reaction score
4
Location
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.
 
Top