TOO heavy?

[gokartt]

Hi there. I think my go kart is going to be too heavy. Here are my calculations:

10 kg seat
10 kg tires
20 kg frame
15 kg floor pan
15 kg engine
55 kg driver
5 kg steering setup
3 kg rear axle
2 kg other stuff
Total- 135kg
And my engine is a briggs 5hp. What will be its maximum speed? What gear ratio should i use for optimum acceleration?

 

[MTNSleder]

300 lb that's a bit of Weigh..

Homemade?? If not what Kart?? Why so heavy.. mines around 150 lb, it's just a little bugger...

 

[bob58o]

How tall are the tyres?

I have a spidercart's Granddaddy buggy.
https://www.spidercarts.com/downloads/granddaddy-go-kart-plans/

It's got a 1.25" 14 gauge steel frame. I dunno how heavy it is. Its pretty heavy. I assume it is around 225kg with wheels, engine, and driver???? It is probably less

I had 16" wheels and I geared it 7.5:1 using a 6.5HP 212cc engine and a 30 series torque converter.

It did around 35mph.



We basically need to know your tire diameter.

 

[mckutzy]

What kind of seat weighs 22lbs???
and why the floor pan 33lbs???

Im thinking you need to check the weights and post some pics on this???

 

[gokartt]

I have 14inch tires and I have got an actual car seat.

 

[Kansaskart]

Yeah you need a bigger engine lol or an 100 tooth sprocket, torque converter and don't mind a 15mph top speed.

 

[bob58o]

I dunno. I think 6:1 with a 30 series Torque Converter will be ok.
16.7:1 at Clutch Engagement. 5.4:1 in Overdrive.
That would top out at like 27 - 28mph at 3600 RPM.
Might not be a bullet from a stop, but should do OK.

Or if the engine is going to turn more like 5000 RPM (like some do without a governor), Then I'd gear it more like 7:1.
19.5:1 at clutch engagement. 6.3:1 in Overdrive.
That would have better acceleration/climbing and top out around 33mph at 5000 RPM.

Got to watch out for sprocket to ground clearance. A 10" Diameter sprocket with 14" Tires leaves 2" clearance, for example.

 

[Espeefan]

The conversion from kilograms to pounds puts your go kart right at 297 pounds, which doesn't seem too out of line to me, for an off road kart. I believe I've read the specs that say a Manco Dingo has a dry weight of 312 pounds. Sure, there are some places where you could save a little more weight, but overall, I wouldn't say it's too heavy.

 

[itsid]

Hi there. I think my go kart is going to be too heavy. Here are my calculations:

10 kg seat
10 kg tires
20 kg frame
15 kg floor pan
15 kg engine
55 kg driver
5 kg steering setup
3 kg rear axle
2 kg other stuff
Total- 135kg
And my engine is a briggs 5hp. What will be its maximum speed? What gear ratio should i use for optimum acceleration?

IDK how you came up with those numbers tbh..
apart from the engine and driver everything seems off a fair bit to me.

anyways the final weight you're getting at doesn't.

80kg for (unsuspended road) go kart is reasonable.

135kg with driver is good actually

depending on the engine (15kg sounds like gx200 clone)
I'd put the ratio ~5:1 which puts you at around 42 km/h (26 mph) on 11" wheels
or 50 km/h (31 mph) on 13" wheels

I wouldn't gear any higher than that tbh..

but feel free to play with some weight/power/wheelsize numbers
at app.kartcalc.net (available on mobile device only!)

'sid

 

[gokartt]

Thanks for the response. BTW it's a 5hp biggs engine I'm using on this project.

 

[itsid]

okay.. doesn't change much tbh
(in fact nothing in my post would be different, not even gear ratios if we talk Torque converter)

if you however want just a centrifugal clutch, your 14" wheels call for something like a 8:1 ratio

So yeah... TC

'sid

 

[gokartt]

What if I want a belt pulley system? What will be the ratio?

 

[mckutzy]

Just keep it to the one thread about the same question.....

What kind of belt drive? A tc or a Belt clutch and belt connected to the rear end?
The latter has been done just recently, a gent with his radio flyer wagon....
http://www.diygokarts.com/vb/showthread.php?t=36839

 

[Kansaskart]

I apologize I missed the 'driver' in your list. If that's the case my kart would smash yours lol.

 

[kartkid11]

Your floor pan shouldnt weigh almost the same as the frame. With your design is the floor pan holding up the seat? If not the floor pan really doesnt support much weight other than the heels of your feet. Also car seats have a lot of unnecessary weight for go kart applications. Id recommend something like this 1 piece plastic seats from Summit racing, it will still provide all the comfort and support of a car seat, while saving A LOT of weight, plus they are only $35.

 

[bob58o]

What if I want a belt pulley system? What will be the ratio?

I'm guessing the same as with chains and sprockets.
So like 5:1 or 6:1 with a torque converter variable pulley system.
Or like 8:1 or 9:1 with fixed pulleys.

 

[gokartt]

I'm guessing the same as with chains and sprockets.
So like 5:1 or 6:1 with a torque converter variable pulley system.
Or like 8:1 or 9:1 with fixed pulleys.

When I have 6:1 , the pulley almost touches the ground. (No CTV) So I have chosen 5:1 which leaves about 2 inches ground clearance.
....wish me luck

 

[itsid]

yeah well.. no need to.. it'll fail very quickly.
A belt has a less efficient power transfer rate by nature (slip)
and you'd need round about 6:1 with small wheels already with a chain driven kart.
with a belt you might want to give it a bit of extra (to compensate for the losses due to slip)
Assuming you run fairly large wheels
(a typical belt clutch has a crappy diameter pulley for go karts [IIRC 3" active diameter])
which leads me to assume a 15" pulley on the rear (5:1 right?)
2" of clearance makes it a 18" maybe even 20" rear wheel instead of the 14" you talked about earlier.

2" clearance on a 14" wheel makes it a 10" pulley on the axle, with a 3" clutch on the engine that'd be a 3.3:1 ratio which will fail just as miserably.

So no.. that won't work... not at all

'sid

PS it helps if you listen to the advise given btw

 

[gokartt]

yeah well.. no need to.. it'll fail very quickly.
A belt has a less efficient power transfer rate by nature (slip)
and you'd need round about 6:1 with small wheels already with a chain driven kart.
with a belt you might want to give it a bit of extra (to compensate for the losses due to slip)
Assuming you run fairly large wheels
(a typical belt clutch has a crappy diameter pulley for go karts [IIRC 3" active diameter])
which leads me to assume a 15" pulley on the rear (5:1 right?)
2" of clearance makes it a 18" maybe even 20" rear wheel instead of the 14" you talked about earlier.

2" clearance on a 14" wheel makes it a 10" pulley on the axle, with a 3" clutch on the engine that'd be a 3.3:1 ratio which will fail just as miserably.

So no.. that won't work... not at all

'sid

PS it helps if you listen to the advise given btw

It's a 2.5 inch engine shaft pulley. Which means 4:1 ratio. If what you say is going to happen I might want a jackshaft with a chain and a sprocket on the 10 inch pulley.

So do you think that will work? If yes what ratio do I want for the chain and sprocket?

 

[mckutzy]

As he said... 6:1 start for a chain drive ratio.