Senior Project Go Kart Build Thread

[Romba]

Hey everyone! I am a senior in High school and one of my school's graduation requirements is to do a "senior project." For mine I've decided to build a go kart.

I've selected the UBuildItPlans Shredder as my base design, with the idea to stretch it and add a second seat behind the first. Finally got my plans and am about to get started, has to be finished by early April. Time is ticking and I've, admittedly, been slacking a bit. I'll be posting my progress and asking questions, so input will be greatly appreciated! Thanks!

 

[justinlogue5_0]

Good Luck Look forward to seeing it.

 

[OzFab]

I've selected the UBuildItPlans Shredder as my base design, with the idea to stretch it and add a second seat behind the first.

That may not be a good idea; by stretching the frame's length or width, you instantly change the way the steering geometry works; you need to keep that in mind...

NO matter what you do, stretching the length will increase the turning circle &, more importantly, the roll angle; stretching the width will tend to reduce the turning circle & roll angle...

 

[Poboy kartman]

That may not be a good idea; by stretching the frame's length or width, you instantly change the way the steering geometry works; you need to keep that in mind...

NO matter what you do, stretching the length will increase the turning circle &, more importantly, the roll angle; stretching the width will tend to reduce the turning circle & roll angle...

Yep....this is exactly why top fuel dragsters are so narrow and long......at 300+ mph.....when you're trying to go straight.....you want turning minimized.....

 

[Romba]

Fabroman and Poboy:

Thanks for the insight, this is exactly what I was hoping for by posting on here. I understand what you mean about the turn radius, but what do you mean by "roll angle?"

The idea is to make it just long enough for a second seat and increase the width just enough to let the passenger have somewhere for their feet. Do you, in your much-more-professional-than-me opinions, think this will pose a large problem?

I will say that this isn't a racing kart, and I won't be trying to win any competitions, so as long as it won't fall and be more driveable than a reliant robin, I will be happy!

EDIT: a word

 

[Romba]

Hey all:

It's been crazy and I'm way behind. My project is due in two weeks, but one of those is spring break. I am going to get it done over the break. I am ordering parts tomorrow, but have a question. Plans call for knobby tires since the kart has no suspension. I'm working with a retailer who is helping me out with a discount, but they just went out of stock of the wheels I need, so I'm looking at doing v-tread tires instead. They are actually a tiny bit cheaper, but would those be a suitable replacement? Thanks!

Edit: I'm going to throw up some pictures of what I've got so far when I get to my home computer that has them on it.

 

[B.M.800]

I don't think there would be any problem using different tires.

 

[justinlogue5_0]

I may be wrong but they (who ever They are) might have told you to only use knobby tires mainly for traction. You wouldn't want to use slicks for off road and knobby for street racing. As long as you have some kind of tread you will be ok. Might even have more fun sliding around trees.

 

[Romba]

Alright all, sorry I haven't kept updated, but I will do a big update very soon, I promise. Got everything all back together (after paint) today, and on the very first start ever (brand new engine) the driver (unit on the engine shaft, I think it's called the driver) engaged right away. My measurements seem to be good, 9 3/4 inches between the center of the shaft of the driven and the shaft of the driver.

From what I've read, it could be idling too high (would it be a set screw or something to adjust idle down?) or wrong distance for the belt. If other troubleshooting tomorrow afternoon fails I may decrease the gap a tad as a "last resort" guess.

Other possibly helpful observations: without a belt on, the driver (again, the unit on the engine shaft) expands all the way at idle. With the belt on it only expands a bit, but enough to engage the belt. The engine seems to be EVER so slightly cock-eyed compared to the jackshaft, would that have such an averse effect?

For context, it is a clone 40 series torque converter, genuine comet belt, on a duromax 16hp engine.

Thanks a million for the help everyone, I have a week before I have to turn it in and I'm just super frustrated that an otherwise very successful build is having issues now, when it is down to the wire.

 

[Romba]

Looking at pictures (kart is at the shop at school) it also seems that my uh, driven, could be uh on uh backwards. Would that affect the driver engaging early?

Edit: is it normal to be able to take the belt on and off relatively easily/without disassembling anything?

 

[B.M.800]

Looking at pictures (kart is at the shop at school) it also seems that my uh, driven, could be uh on uh backwards. Would that affect the driver engaging early?

Are the pulleys symmetrical or asymmetrical? If they are like "V" (and If I understand correctly) it should work just fine.

 

[Romba]

I do believe they are. It's a 40 series, so they should be.

Further research seems to indicate if I turn down the idle on the carb it should stop the early engagement I'm getting. Does that make sense?

 

[justinlogue5_0]

If your motor is idling to high, yes it will engage your clutch or TC whether your on it or not. They are centrifugal design. If your kart is on the ground and it tries taking off with out you then you are idling to high or you have a defective clutch/TC. If your kart is off the ground and the wheels start turning, that's in a lot of cases normal. Put it on the ground and re try it.

I don't remember which motor you have but all motors have an idle adjustment screw on them. Back it down till the wheels quit pulling and then turn it just a little more. Rev it a couple times and make sure it goes back to idle. If it tries dying , bump the idle backup just a little. That will get you pretty dang close for ya.

 

[itsid]

well if your driven is on backwards, you should flip it

an asymmetric system MUST NOT be installed flipped (s30),
a symmetric system can be installed with a flipped driven, but ONLY, if you have a reverse wound spring installed.

keep in mind, that the series 40 system has it's cam & spring inboard "normally" as opposed to a series 30 with an outboard spring & cam..
(outboard = pointing AWAY from the engine)
So if your cam and spring is pointing to the engine, and your spring is red... you're safe.. everythings installed as it should.

otherwise you need to either flip it or install the reverse wound spring (yellow)

'sid

 

[Romba]

Welp, what I thought was backwards initially was correct then. Time to flip it BACK around so that my spring is pointing toward the engine. Pictures I'd seen were both ways and nothing was definitive. Thanks Sid!

Hoping today is the day... Lots of frustrations yesterday, but they were all things that were going to happen at some time. I've got to "turn it in" (drive it from the welding shop at the college up a hill to my high school which is on the college's campus) Monday, but I think I'm good to go at this point.

To do list, because it helps me to think it through:
-Add gussets on the steering rod where I had to re-route it (will take pics and post later)
-flip driven around
-Cut welds on pillow blocks, drill for bolts, buy washers so I can shim the jackshaft up to add tension to the chain
-Tear up the parkinglot!

Thanks all, big update soon hopefully!

 

[Romba]

Class is super slow right now, so I'll tease with some numbers before I upload pictures.

Bear in mind this is completely built from scratch. While I'm sure some of yall have built more impressive things from scratch, I'm extremely proud of it.

Overall length: 120 in/ 10 ft.
18"x9.5" rear tires.
No suspension.
No seatbelts (for now.)
Full rollcage.
Two seats, one behind the other raised up on a "box" which doubles as storage/future battery box.
Roof rack/ Roof box like you'd find on a Jeep.
16 hp Duromax with 40 series TC, 6:1 ratio.

It's been loads of fun to build, and hopefully will be done today!

 

[itsid]

6:1 on 18" wheels with a heavy kart (assuming it's rather hefty considering your explanation)
reads like a bit of a stretch to me.. even with a s40 and a 16hp engine...

my calculator isn't moaning, but my guts are
I'd say try to stay below 800lbs total weight (incl passengers) and give it a shot.

But just in case buy a second sprocket (maybe 8:1) split sprockets are easier to change

'sid

 

[Romba]

Actually, Sid, I am having chain slipping issues when I stomp on it from a standing start. Once I'm rolling I can stand on it and it won't slip, it's just if the kart is stopped. Perhaps I need a jackshaft sprocket with more teeth. Do you think that would help the slippage?

EDIT:
Looks more like a new axle sprocket than a jackshaft sprocket. This will have to be something I do AFTER I turn it in officially.

 

[J_Walker]

Actually, Sid, I am having chain slipping issues when I stomp on it from a standing start. Once I'm rolling I can stand on it and it won't slip, it's just if the kart is stopped. Perhaps I need a jackshaft sprocket with more teeth. Do you think that would help the slippage?

EDIT:
Looks more like a new axle sprocket than a jackshaft sprocket. This will have to be something I do AFTER I turn it in officially.

chain slipping is a tension issue, not a torque issue. trust me, chains can snap with too much torque....

There was this time, on a yellow CBR600F4i taking off in the front row at a red light, and the chain broked and sucked into the front sprocket inside the case. and caused the engine to lock up and slide the rear tire.

dats some scary stuff on two wheels under your left leg!

 

[Romba]

My chain is tight as an analogy for being really tight. It is REALLY tight.

In that case, it is what my other suspect was. I (stupidly) didn't key the sprocket when I put it on the jackshaft. The set screws probably aren't enough to hold it in place, and the torque from the 16 horsepower motor is probably causing the sprocket to rotate on the jackshaft. Since it is only from a standstill that is "slips" (where the most instantaneous torque is applied by my TC,) that's gotta be it. I'm "turning it in" on Monday, so for now, being ginger on the throttle from a standstill will be fine, but after they're done grading it I'll tear the rear end back apart and key that jackshaft.

I'd bet that would be scary indeed! I want a motorcycle......

Thanks everyone