hey guys i'm building a buggy and i wanna have an idea of how fast its gonna go with 26hp 25 in rear tires, 3:1 gear ratio, 3600-4000rpms and the weight of the buggy plus mine is about 220kgs so does anyone have an idea on how fast i can possibly go. and also i'm not using a centrifugal clutch or a torque converter its a manual tensioner pulley system........... the speed can be mph or kph
how fast
- Thread starter timmzzy
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firemanjim
Just kartin' around....
Not that youre really gonna hit it , but the math says 89 mph @ 3600rpm.... Where did you get the 3:1 ratio from? You should really post pics of what youre working on, and what youre working with..... No clutch at all? Yeah..... I dont see that working right......
i got the ratio from the normal bike gearing (14driver and 42 driven) common around where i live that's nigeria and i cant order for a centrifugal clutch or a torque converter all the way from the US so i just gotta use the tensioner pulley system and i've seen a lot of videos on youtube where that has been used and it works....... sorry i dont personally own a camera or a phone with a clear camera to take the pics...... but the thing is can i really reach 89 mph with that weight
firemanjim
Just kartin' around....
If it is an engine from a dirt bike / motor bike, then that is a different story. what engine do you have? Those engines run a lot higher than 4000rpm.....
firemanjim
Just kartin' around....
If youre not using a bike engine, then the gear ratio you stated is about as useful as an empty fire extinguisher.....
And then you say no clutch, but using 2 gx390's? I smell a pipe dream......
start from the begging and tell us exactly what your plans are. Its gonna help us help you......
With a 3:1 great ratio, your kart will barely move. You are going to have to get lower. You will need at least 6:1 to get going. How are you going to set both engine up for the belt tensioner?
KartFab
Active member
Didnt like the answers I gave you so you are asking them again? You do realize that if you get an answer you do not like, then ask more people that also know what they are talking about that the answers are going to be the same.
Nobody in their right mind is going to tell you that this will 'work' --- you will be on your own as nobody that values their life, or their belts will gear like that.
What you are still failing to understand, is that the problem is NOT the 'theoretical' top speed. The problem is the friction and torque that the belts will experience as they constantly slip and slip and slip and slip and slip and slip and slip and slip and slip and slip and slip and slip, and then finally start to engage, by then you will be going so fast with the engines barely idling, so you will have to keep the engines from stalling out by applying gas, and working the tensioner so it doesnt stall the engine, and then all the forces are absorbed by the belts, heating up, smoking, fraying, stretching out-- who knows how, but what we all agree on here is that this is NOT something that we would reccomend doing.
So stop asking for advice if you are going to ignore it.
If you really want to do this, please just ignore all common sense and advice, and give it your best shot. Try it out by ignoring us. Nobody that knows what they are talking about is going to say this is good, nobody that has build a go kart before and geared it properly is going to think this is a stellar gear ratio.
The problem is not the power (in case you missed it) the problem is the gear ratio.
Do you drive a manual transmission car or truck?
Can you start it in 5th gear from stop? That is EXACTLY what you are asking.
The answer is NO dont do it, yes it is possible and you are going to break or burn something up finding it out the hard way.
If you are going to be so stubborn about it, what is the worst that could happen? YOU will have to answer that by doing it (which we do not condone). Nobody is going to say oh hey yeah thats super great, just yep its all fine, dont worry about it, yes that will work, no problem at all.
Nobody in their right mind is going to tell you that this will 'work' --- you will be on your own as nobody that values their life, or their belts will gear like that.
What you are still failing to understand, is that the problem is NOT the 'theoretical' top speed. The problem is the friction and torque that the belts will experience as they constantly slip and slip and slip and slip and slip and slip and slip and slip and slip and slip and slip and slip, and then finally start to engage, by then you will be going so fast with the engines barely idling, so you will have to keep the engines from stalling out by applying gas, and working the tensioner so it doesnt stall the engine, and then all the forces are absorbed by the belts, heating up, smoking, fraying, stretching out-- who knows how, but what we all agree on here is that this is NOT something that we would reccomend doing.
So stop asking for advice if you are going to ignore it.
If you really want to do this, please just ignore all common sense and advice, and give it your best shot. Try it out by ignoring us. Nobody that knows what they are talking about is going to say this is good, nobody that has build a go kart before and geared it properly is going to think this is a stellar gear ratio.
The problem is not the power (in case you missed it) the problem is the gear ratio.
Do you drive a manual transmission car or truck?
Can you start it in 5th gear from stop? That is EXACTLY what you are asking.
The answer is NO dont do it, yes it is possible and you are going to break or burn something up finding it out the hard way.
If you are going to be so stubborn about it, what is the worst that could happen? YOU will have to answer that by doing it (which we do not condone). Nobody is going to say oh hey yeah thats super great, just yep its all fine, dont worry about it, yes that will work, no problem at all.
THAT!!
don't try;
the belt will be whipping at you way faster than you're going to go in that second you have before it snaps.
'sid
OzFab
Well-known member
With 25" rear tyres, no...
No, its not. With 25" tyres you might even need to go lower than 6:1
MUCH lower indeed.
9:1 to 10:1 is realistic with a cent clutch or it'll just glaze and burn.
'sid
9:1 to 10:1 is realistic with a cent clutch or it'll just glaze and burn.
'sid
sorry for this question but why cant the 5:1 go with the 25'' tires or is it that there wont be enough acceleration or the buggy will be going too fast...... sorry if its annoying buh im really new at this stuff and the way you guys in the us can get material we cant here in nigeria so we just have to salvage stuff
---------- Post added at 03:07 PM ---------- Previous post was at 02:48 PM ----------
and again im not using a centrifugal clutch im using a tensioner pulley system
---------- Post added at 03:07 PM ---------- Previous post was at 02:48 PM ----------
and again im not using a centrifugal clutch im using a tensioner pulley system
the problem is the necessary take off speed.
I explained that elsewhere already (too lazy to find it and too lazy to fully explain it again)
so here's the short version:
your clutch engages at a certain rpm, the bigger the wheels the higher the necessary speed for the kat to catch up with the rotating clutch bell... and since acceleration is limited you cannot catch up quickly enough to not burn your clutch into total uselessness.
And although you can regulate that takeoff speed slightly to your benefits with a tensioner system,
it too will fail...
the belt is not very good at transferring power, it's also not good at evaporating heat..
So less effectively transferred power, at a lower rpm (likely too little torque to get the kart moving)
and the belt will just melt and/or snap and you'll replace it constantly.
And that's why there is no point in adding horsepower, since that's nothing to do with it at all (once a certain threshold is met)
No, you cannot run it on 5:1 PERIOD
(you can try, it'll fail!)
'sid
I explained that elsewhere already (too lazy to find it and too lazy to fully explain it again)
so here's the short version:
your clutch engages at a certain rpm, the bigger the wheels the higher the necessary speed for the kat to catch up with the rotating clutch bell... and since acceleration is limited you cannot catch up quickly enough to not burn your clutch into total uselessness.
And although you can regulate that takeoff speed slightly to your benefits with a tensioner system,
it too will fail...
the belt is not very good at transferring power, it's also not good at evaporating heat..
So less effectively transferred power, at a lower rpm (likely too little torque to get the kart moving)
and the belt will just melt and/or snap and you'll replace it constantly.
And that's why there is no point in adding horsepower, since that's nothing to do with it at all (once a certain threshold is met)
No, you cannot run it on 5:1 PERIOD
(you can try, it'll fail!)
'sid
OzFab
Well-known member
Here is what Alex said in his one post
many people simply have no idea about physics....
There is absolutely no point in gearing a single speed vehicle to go 60mph;
not with a cent clutch;
and the reason is as simple as it is obvious.
at one point in time the clutch wants to engage, when just a moment earlier it was NOT engaged at all.
And that's where physics will kick your 455!
gearing for 60mph @ 5500 rpm means
at the very same time gearing for 20mph @ 2000rpm
and that can be read as the most stupid idea on a conventional cent dry clutch you could have!
Still don't get it?
ALERT
People with common sense do not need to read the following novel of heat and demise
Well then, allow me to explain:
Your kart doesn't move at all, the engine is idling happily at ~1200rpm and you're anxious to see what would happen if you kartapult your behind to 60mph in a kart that's made for a 10yo and far from being made for speeds even close to that number.
Anywhoo, you hit the throttle and the engine revs up to 1800rpm, the clutch shoes now move at roughly 9.5 m/s (21.25 mph) and are trying to get hold of the still stationary clutch bell.
Since the clutch bell is held stationary by the chain and the yet unmoving axle/tyre
all it can do is rub slightly but with a high rate, which isn't actually transferring power, it only produces heat.
you accelerate further, and all that does is applying more pressure on the clutch shoes (centrifugal force)
say 1900 rpm the shoes will ow move at 10m/s (22.36 mph) and still can't get hold of the bell very well, since it's still not moving, at least not very fast.
So you produce more heat, and the hotter the clutch will get, the less power will be transfered and the more power will be converted to heat.
and that's where the dog bites it's tail
eventually the clutch will be at it's "fully locked" position, or what's meant as such
at around 2000rpm (10.5 m/s or 23.5mph)
and that's the point where your kart finally begins to move.
the clutch is already smoking hot, likely discoloured by now and thus all warranty is voided;
but the kart starts to crawl very very slowly, and you feel like you showed us all;
But you forgot... the kart MUST GO 20mph for the clutch to fully engage.
So it's still slipping and likely you still step on your throttle since your mind tells you "more is more"... and it is.. the more you try to accelerate, the more heat you apply.
Unfortunately, it's not more power, since that ratio is off, it's less power, and since the clutch is slipping it's even less than you'd expect (or even calculated) at all.
Who cares, the kart is moving finally... and you do get faster (since you started downhill or something) and eventually even hit the 20mph needed to fully engage the clutch;
and it only took about 30 seconds...
all good right?
WRONG!!!
Your clutch is now annealing likely even deforming
or to use a term you might have heard... it's TOAST!
you've driven your kart, that much is true...
but the next time you start from a dead stop it'll slip some more.
I doubt you can use that clutch a second time to be honest, but in case I'm wrong;
a third time is out of the question for sure.
So a new clutch has to be bought.. a racing clutch this time... those can withstand lots of abuse right?
right... it'll hold twice as long and costs four times as much!
Do the math !!
Now, for the price of a racing clutch you can go and buy a torque converter;
much better idea, it'll reduce the stress a good amount with it's internal gear ratio.
(even enough to maybe get away with that ratio of yours)
So, after burning a cheap standard maxtorque SS and maybe a Noram racing clutch you end up buying a TC
and finally try to hit 60mph..
just to find out that at 45mph the kart starts to act strange,
but you're the toughest manliest man alive, right?,
So who gives a flying shirt.. you still have 1500 rpms to go...
that's where the cheaply made kart will do the rest.
the improper steering geometry will wobble a crack or loosen a crucial bolt;
that flimsy plastic steering wheel brakes since you clench a little too hard
(no matter how tough you think you are, this will scare the brown out of your backend)
and the rest is all but violets in bloom and bird songs.
It's simply not made for speed, not meant for speed...
But go ahead, get your Darwin Award as long as it's still hot.
'sid
OzFab
Well-known member
Are you not paying attention? 6:1 IS NOT LOW ENOUGH WITH 25" TYRES 
Are you not paying attention? 6:1 IS NOT LOW ENOUGH WITH 25" TYRES
Like we have said.....with 25" tyres you will need a lower ratio....like 9:1
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