Gearing options, recommendations - Barstool Kart

[t1704]

Hello all,

Working on a new barstool kart project and wanted to poll the group on recommendations around gearing. My current plan is to run a 10T CC to a 54T sprocket using a #41 chain as I thought this would be a good middle of the road gearing setup (5.4:1 w/ 11' tires). As you can see in the pic, I'm cutting it pretty close with ground clearence and while I only plan to drive this on the street, a sizeable rock in the road or pavement variations could be a problem.

For now, I'll be running a bone stock predator 212 and this needs to be able to pull a 200lb adult without burning up clutches. Do you all think a 40T rear sprocket (4:1 GR) is too aggressive?

Thanks in advance for the insight.

 

[itsid]

kind of a stretch already...
Assuming another 100lbs for the vehicle and the clothing said 200lbs person hopefully covers his meaty vessel with

5.4:1 is already a bit too high for my conservative calculator to accept.
(it asks for 5 additional teeth namely a 5.9:1 ratio to keep the clutch alive)
But again it's very conservative on numbers
to even allow (up to a degree)
cheap clutches, assume
less than ideal road conditions
a sticky bearing
or whatever makes the setup less than perfect.
A perfect setup with high quality bearings and it should work with the ratio you have

if you want to use the 40T axle sprocket to gain some clearance,
you would want to swap the clutch for a series 30 TC (chinese clones off ebay are cheap),
it will make it work but with a cent clutch, there's no way the clutch would survive for very long.

'sid

PS find yourself a sprocket guard that way even if it gets hit by the road or the random sticks and stones, chain and sprocket will likely survive

 

[JTSpeedDemon]

 

[t1704]

kind of a stretch already...
Assuming another 100lbs for the vehicle and the clothing said 200lbs person hopefully covers his meaty vessel with

5.4:1 is already a bit too high for my conservative calculator to accept.
(it asks for 5 additional teeth namely a 5.9:1 ratio to keep the clutch alive)
But again it's very conservative on numbers
to even allow (up to a degree)
cheap clutches, assume
less than ideal road conditions
a sticky bearing
or whatever makes the setup less than perfect.
A perfect setup with high quality bearings and it should work with the ratio you have

if you want to use the 40T axle sprocket to gain some clearance,
you would want to swap the clutch for a series 30 TC (chinese clones off ebay are cheap),
it will make it work but with a cent clutch, there's no way the clutch would survive for very long.

'sid

PS find yourself a sprocket guard that way even if it gets hit by the road or the random sticks and stones, chain and sprocket will likely survive

Thanks Sid - I was affraid this might be the case. So, a couple thoughts/questions:

1) So, a 9T CC would bring me to 6:1 on the current setup to be comfortable (although still have the clearence issue), but based on a quick search, I don't believe they exist (at least for a economically priced one, such as the Max Torque I have now)

2) I'm not opposed to the TAV, but initially thought it would be overkill for this little project. I'd have to see if I have clearence on the left side of this kart to accomodate, but not opposed to it. This is what we have on my son's kart and so I'm familiar with their set up. If I do go this route, most of them have a 10T driven sprocket. You're saying I could comfortably reduce the axle sprocket at this point? If so, what would you recommend for both additional clearence as well as optimal gearing?

Anything I missed?

 

[JTSpeedDemon]

'sid's the expert here so listen to him, but I think that a 30 series TAV with a 10T sprocket should get you by just fine.
Of course you'd still have a clearance issue though.
In my opinion, I would not reduce the gearing any more.
But again :
Listen to His Moderatorness.

 

[t1704]

'sid's the expert here so listen to him, but I think that a 30 series TAV with a 10T sprocket should get you by just fine.
Of course you'd still have a clearance issue though.
In my opinion, I would not reduce the gearing any more.
But again :
Listen to His Moderatorness.

I agree - Sid is a library of knowledge and has helped me significantly on prior projects, as have several of the other mods. These guys are awesome!

 

[itsid]

you are welcome to play with some numbers yourself..
my calculator is open to anyone with a smart phone
(yeah it 'requires' an installed GPS and accellerometer since it CAN use it to makeshift a small kart dyno... so it only really runs on mobile devices
you can deny gps and accelerometer access if you like it'll still calculate)

just navigate your browser to app.kartcalc.net
and in the bottom menu click on menu to set your weight dimensions to lbs (else it assumes metric kg)
then punch in the numbers in the quickcalc
With a barstool I wouldn't want you to be too fast really
(high center of gravity, small footprint makes it a tripping hazard )
But I'd say if you really want to you could get away with a 3:1 ratio 11" wheels
and a series 30 TC
(it's hard on all parts and dangerously fast [~43.6mph] but would theoretically work)
4:1 (the 40T sprocket ) gives you much better acceleration though and still about 32.7 mph
[all at 3600 rpm.. @5500 the 'slower' 40T would hit 50mph]

Sprocket sizes are easy to estimate with math.. but frankly you get a much closer to real world value with the Azusa Sprocket sheet (they have one for all relevant chain sizes)
on #41 (40, 420, 410 etc)
a 54T is 8.88" (say nine which gives you about an inch of clearance with the road)
a 40T is 6.65" (let's call it seven which gives you two inches of air between it and the road..)

And inch should suffice IMHO.. but when in doubt a sprocket guard really helps alot.

I'll attach the #40 chart but they're all on azusaeng.com

As you can see the root diameter of a ten tooth #40 sprocket is just
1.3"
a 3/4" shaft, a hollow stem (for the key to grab on to)
a bushing and a bit of meat for the sprocket to not just be individual teeth.
all in all ~1/4" of thickness
and there you are 1.25" in diameter are occupied by necessary stuff..

Yes you can move the clutch sprocket out to run unsupported by the actual crankshaft and shrink down to whatever you like...
but frankly it's seldomly necessary and thus (being rarely needed) is more often pricey

'sid

 

[Joe-405]

I have that exact frame and I have the box stock project engine with a tav setup. Mine makes about 11-14 hp. Will run 60mph and stand straight up in the air. I love it.

First one I built (same drivetrain in 2nd and current version)
http://www.diygokarts.com/vb/showthread.php?t=26426

2nd and current version (just added vm22 mikuni carburetor kit) makes more power now
http://www.diygokarts.com/vb/showthread.php?t=35525

 

[itsid]

Awesome!
Now we know the TavKit fits

'sid

 

[t1704]

Great, thanks guys. I have no interest in going 60MPH on this, in fact, I don't even want to go 35MPH. Based on this, I'm gathering a TAV and a 40T rear sprocket is going to be the best outcome. I will proceed accordingly.

 

[JTSpeedDemon]

Let us know how it goes!

 

[frostyflammable]

Here is my barstool setup... 13" tires, 11T clutch 67T sprocket, 35 chain. I still have the governor in the engine and so far have not had the stones to max it out.

--Daniel

 

[Joe-405]

Great, thanks guys. I have no interest in going 60MPH on this, in fact, I don't even want to go 35MPH. Based on this, I'm gathering a TAV and a 40T rear sprocket is going to be the best outcome. I will proceed accordingly.

Build a wheelie bar ! You’ll need I guarantee.