Go Back   DIY Go Kart Forum > Building Plans And Advice > Go Kart Discussion

Notices

Reply
 
Thread Tools Display Modes
  #1  
Old 02-19-2020, 09:12 PM
ebull ebull is offline
Junior Member
 
Join Date: Feb 2020
Posts: 5
Thanks: 0
Thanked 0 Times in 0 Posts
Default need help with gearing ratios

I am new to go karts and bought an unknown frame to try and fix up. When bought it it had 22in tires that were bad so I replaced with the same size. I put a pred 212 and tc on it and it doesn't have the power to go. I have a 72 tooth rear sprocket and a 12 on the tc I believe, giving it 6:1 ratio. If i added a jackshaft would that be able to gear it to where it will move or is this set up a lost cause. If it would work, what overall ratio should I be looking at( 8:1-12:1) for an optimal jackshaft setup. I sorta jumped right into building and didn't do enough research,(hopefully wont make that mistake again). It's an old off road frame 150+ pounds with motor, drive adding another 200.

At this point I don't care it will only go 10mph I just want to finish the project, then I can look at a much larger motor.
Reply With Quote
  #2  
Old 02-20-2020, 05:09 AM
itsid's Avatar
itsid itsid is offline
Moderator
 
Join Date: Jul 2013
Location: Ruhrpott [Germany]
Posts: 11,048
Thanks: 1,483
Thanked 4,589 Times in 3,464 Posts
Default

HI and welcome!

I wouldn't add another jackshaft tbh.
I'd just swap to a larger axle sprocket tbh, maybe a smaller TAV Sprocket.

22" rears are always a pain (and frankly pointless most of the times)
so maybe next time 18" rears might suit you much better

Anyways..
350'ish pounds to move around on 22" rears with a 6.5horse and tavkit..

if that's indeed all the weight you want to be moved (not a two seater kart then?)
22" on single seaters are rare.. that's why I'm asking.

Now all you need with a TavKit would be a 6.8:1 ratio

Frankly I'd get a smaller TAV Sprocket
since you said yours has 12 Teeth I'm assuming that's a #35 chain, right?
BM sells a 10T #35 TAv sprocket:
https://www.bmikarts.com/TAV-Replace...pe_p_1421.html

that would lower your rato to 7.2:1 and the kart (with as little modification as possible)
would have the power to move (35'ish mph btw)
and it'd do so with up to ~410 lbs (total weight.. kart plus passengers)

'sid

PS as always with BMI.. call them and ask for shipping, most complain about their insane shipping fees on the website.
or buy from mfg (or any supplier you like)
https://www.mfgsupply.com/az2189-k.html
__________________
Jokes about german sausage are the wurst.
Reply With Quote
The Following User Says Thank You to itsid For This Useful Post:
Flyinhillbilly (02-20-2020)
  #3  
Old 02-20-2020, 08:17 AM
ebull ebull is offline
Junior Member
 
Join Date: Feb 2020
Posts: 5
Thanks: 0
Thanked 0 Times in 0 Posts
Default

It is a two seater cart. I think it is an old dune buggy type kart, and i think it had a gy6. Which at i thought were about the same as a 212 power output wise. Which is why i chose that instead of somthing bigger. I will try it, thanks.
Reply With Quote
  #4  
Old 02-20-2020, 09:40 AM
itsid's Avatar
itsid itsid is offline
Moderator
 
Join Date: Jul 2013
Location: Ruhrpott [Germany]
Posts: 11,048
Thanks: 1,483
Thanked 4,589 Times in 3,464 Posts
Default

unfortunately that's a different game then

a gy6 has about twice the power of a stock 212
(50% more hp and torque PLUS more than twice the rpms, with it's internal gear reduction
it's about roughly two 212s...maybe 2 and a half )

Also a two seater for two adults is not sufficiently powered with anything like that gear ratio.
since it's total weight is closer to 700lbs
(a Manco carbide 475lbs empty +400 lbs of passengers max makes 875 lbs for example)

and to move that on 22" wheels you need a LOT more oomph
a chain ratio of 9.5:1 would be needed

so not only would you need to swp the TAV sprocekt to a 10T,
you'd also need the Axle sprocket to grow to 95 Teeth
the only #35 that size I know is a split sprocket
https://www.mfgsupply.com/gomini/gom...az2699-95.html
which would require a matching hub to be mounted

Since I don't knwo your kart, I can't trell if you have such hub already or would need one *shrugs*

Sorry, I was hoping it'd be as easy as just that one tiny sprocket..
but a twin seater mini buggy is just no single seater go kart (weight-wise)

'sid
__________________
Jokes about german sausage are the wurst.
Reply With Quote
  #5  
Old 02-20-2020, 09:59 AM
ebull ebull is offline
Junior Member
 
Join Date: Feb 2020
Posts: 5
Thanks: 0
Thanked 0 Times in 0 Posts
Default

Yea i was afraid of that. While its not 400lbs (i can pick it up) its been stripped down to the bones, doesnt have a role cage or anything. I think ill buy a 420 cc motor and tc to match and swap the whole setup. At first when i looked up the gy6 i read that they only make some 7 hp or something, then later i found out the could make upwards of 14 and thats when i realised this was kinda a lost cause.

Ill probably just buy a second small cart to use my 212 on and buy a 420 or 670 or something.
Reply With Quote
  #6  
Old 02-20-2020, 10:49 AM
itsid's Avatar
itsid itsid is offline
Moderator
 
Join Date: Jul 2013
Location: Ruhrpott [Germany]
Posts: 11,048
Thanks: 1,483
Thanked 4,589 Times in 3,464 Posts
Default

it's the combination really..
some gy6es put out nothing but 7 horses at 7500 rpm,
some make indeed up to 13 or 14 horses
most on mini buggies I 've seen are rated in the 8 or 9 hp range though.

that and the 50% more torque that all of those have in common compared to a predator
and their internal gear reduction makes it hard for any industrial engine to compete.

before you buy a 420 engine and a new series 40 Torque converter,
I think you should just swap to smaller wheels maybe

18" wheels (as are common on industrial 7 horse engine powered mini buggies)
make it much easier for you to achieve a good result.

sticking with a 700lbs guess for example
your engine and your TC with the 10T sprocket swap and 18" rear wheels would only need
a slightly larger axle sprocket five more teeth; a 77T sprocket will do nicely.

your engine, your TC, your axle sprocket, the 10T TAV Sprocket and 18" wheels
would move your kart if it's less than 620lbs total (still almost @ 30mph ... 29.75 to be exact)

of course that'd be your decision to make,
but I think I'd rather swap the tyres than the engine.. sounds much cheaper to me

'sid
__________________
Jokes about german sausage are the wurst.
Reply With Quote
  #7  
Old 02-20-2020, 11:01 AM
ebull ebull is offline
Junior Member
 
Join Date: Feb 2020
Posts: 5
Thanks: 0
Thanked 0 Times in 0 Posts
Default

Ok, ill look into that, i have 18 or 16 up front so i may just swap them to the back and get smaller up front. Thanks for all the great info.

Where do you get tour calculation for weight plus gearing. Just curious as all the places ive seen dont take weight into consideration
Reply With Quote
  #8  
Old 02-20-2020, 11:07 AM
itsid's Avatar
itsid itsid is offline
Moderator
 
Join Date: Jul 2013
Location: Ruhrpott [Germany]
Posts: 11,048
Thanks: 1,483
Thanked 4,589 Times in 3,464 Posts
Default

I made my own calculator a few years ago..
it's slightly outdated but the dedicated app isn't ready yet..

if you want to give the old webapp a try just browse to
app.kartcalc.net with your phone

it's phone only since it has a no longer fully functional speedometer included..
thus needed a gps signal

'sid
__________________
Jokes about german sausage are the wurst.
Reply With Quote
  #9  
Old 02-20-2020, 11:08 AM
ebull ebull is offline
Junior Member
 
Join Date: Feb 2020
Posts: 5
Thanks: 0
Thanked 0 Times in 0 Posts
Default

Ok thanks
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 11:23 AM.