Go-Krawler Flatfender - Articulating 4x4 Go-Kart

[AgitatedPancake]

Alright I figured I might as well make a thread for this thing because I think it's pretty sweet. This is one of those ideas that's been rolling around in my head for years, but my nieces and nephews are getting close to the right age for driving things around so it's time to make it happen.

So what is it? It's just a pint-sized crawler. Essentially has one links front and rear, crossover steering, transverse leaf springs, a HF predator motor with centrifugal clutch (CVT could be added at some point), and a gearbox with reverse. Completely made from aluminum sheet metal (except the cage and drivetrain stuff). The design still needs refinement before it goes out to laser, but everything is there and in its final position.

-22" tires
-Hoping for ~250lbs (or less, but haven't started adding things up yet)
-About 6ft long, 4ft wide
-Pedal box has over a foot of adjustability in it. Designed for kids, but by some miracle it looks like an adult up to around 6ft can squeeze into it with the pedals fully pushed out to the grill.
-Also building a remote control box that can be dropped in in minutes converting it to an RC car, then removed just as easily when kids want to drive

If it performs like I hope, and holds up, I've genuinely thought about manufacturing them in kit or preassembled form. But I'm not thinking about that too heavily until I have confidence this will work the way I want it to, there's a decent amount of outside the box stuff going on. But this is a build thread for this #1 for my family, I'll bump this thread as things come together!

 

[TrailTamer]

I think it's pretty sweet.

I think so too!

one links front and rear, crossover steering, transverse leaf springs

What axles?? Details

a HF predator motor with centrifugal clutch (CVT could be added at some point), and a gearbox with reverse.

I suggest go CVT right from the start. Centrifugal clutch will be glowing orange in no time. Unless you’ll gear it deep, so the clutch will stay engaged most of the time. Very low top speed and engine running against governed rpm a ton, imho are undesired.

-Hoping for ~250lbs (or less, but haven't started adding things up yet)

A riding lawn mower weigh about that much. A good, realistic goal I’d think.

-Also building a remote control box that can be dropped in in minutes converting it to an RC car, then removed just as easily when kids want to drive

I love this.

I'll bump this thread as things come together!

Please do

 

[AgitatedPancake]

I think so too!

What axles?? Details

I suggest go CVT right from the start. Centrifugal clutch will be glowing orange in no time. Unless you’ll gear it deep, so the clutch will stay engaged most of the time. Very low top speed and engine running against governed rpm a ton, imho are undesired.

A riding lawn mower weigh about that much. A good, realistic goal I’d think.

I love this.

Please do

The axles are custom using some oil filled industrial worm drives, and 1.25" tubing as axle shafts. That's one of the points that I won't be confident in until I try them out, so we'll see.

The CVT vs centrifugal is definitely an interesting one. I settled on the centrifugal with heavy reduction (10-15mph top speed) for this specific one because this will be the kids first gas powered anything, so speed isn't as critical and the reduction takes a lot of stress off the clutch. Especially because I want this thing to actually be capable of slow technical crawling, so burning belts would also be a concern even with the CVT. In the ideal world I'd have a multi speed transmission, but trying to accommodate that pushes this thing even more over the top than it already is lol.

As far as weight goes I'm trying to be pretty conscious about every decision, I want one person to be able to heave it onto a trailer or rack of some kind for easy transportation. I would be damn happy if I landed anywhere in that 250 range, and would be ecstatic if it came in under that. But who knows, it could go the other way.

I think the RC thing is a huge perk to just make this thing as versatile as possible. Kids can drive it, adults can drive it, and anyone can RC car it. So if the kids get bored it doesn't just sit there taking up space, it can be enjoyed by everyone

 

[TrailTamer]

The CVT vs centrifugal is definitely an interesting one. I settled on the centrifugal with heavy reduction (10-15mph top speed) for this specific one because this will be the kids first gas powered anything, so speed isn't as critical and the reduction takes a lot of stress off the clutch. Especially because I want this thing to actually be capable of slow technical crawling, so burning belts would also be a concern even with the CVT. In the ideal world I'd have a multi speed transmission, but trying to accommodate that pushes this thing even more over the top than it already is lol.

I used centrifugal clutch and CVT on my mini bikes.

CVT is the way to go for your purpose. Centrifugal clutch is not suitable for applications where there’ll be a lot of throttle modulating.

I was at my friend’s place and he test drove his project car (70’s? Muscle car) and it stalled and will not restart. It was down the road and it’s a steep hill, no less than 8-10% grade. I used my mini bike to tow it back up to his shop and to my surprise it did. (Yes I had my body well over handlebars to keep front end down).

I reckons you’re planning on to use Predator 212cc which will use a CVT based off Comet’s TAV-30. They have 2.7:1 in low range (when subjected to low throttle and/or high load).

https://www.eccarburetors.com/assets/images/Comet-30-TAV-Manual.pdf

 

[TrailTamer]

ANGELO

 

[ANGELO]

The ebay torque converters are the way to go. The model depends on what size predator your running. (If your planning a 212, I'd look into a 223 wildcat) the torque converter has lower gears up into a overdrive. All the "shift points", engagement rpm and even if you want to limit it getting into overdrive can all be adjusted to get you what you want

 

[ThePanzerFuhrer]

If you’re dead set on a centrifugal clutch get a wet clutch. I put these on our gokarts and they take a hammering and keep on going. They make them for 3/4 and 1” shafts.

Noram 2:1 Reduction Gearbox Kit for 3/4" Shaft | BMI Karts And Parts

www.bmikarts.com

 

[AgitatedPancake]

Hmmm good notes, thanks guys. Yeah I was thinking the 212, or something at least the same/similar form factor. Are there different length belts available if I can't put the reverse gearbox in the same orientation as they're set up for? The reverse gearbox I got is the common import one that actually already has the shaft layout for the cvt/torque converter so it's definitely doable, as long as I can make it all happy with the way things are packaged

I'm not dead set on the centrifugal, but I didn't realize that centrifugals were held in such low regard these days. The little briggs powered cart I had as a kid is my only experience, but it was centrifugal and pretty bulletproof and fun, so I figured I could get away with it for a decent while with low gearing

 

[Skinny]

May be able to find a cheap sled that has a small air cooled engine, cvt, and maybe even a disc brake that would work for you. Reverse may be tough to find. Just a thought.

 

[AgitatedPancake]

May be able to find a cheap sled that has a small air cooled engine, cvt, and maybe even a disc brake that would work for you. Reverse may be tough to find. Just a thought.

Something like that could definitely work, and someone could prob retrofit if they want a little more umph haha. As of now I'm thinking the predator 212 is the way to fly in part due to the bang for the buck, and because it's a nice universal platform that anyone can get their hands on (just in case I make more of these things)

Great call on the Wildcat 223 Angelo, I've been looking at the various different engine options in that form factor, and that one looks to have great bang for the buck, especially with the electric start.

Are all of the torque converters considered equal? This one looks to be Comet based like you mentioned Trail, just a generic example that I've looked at a couple times

https://www.amazon.com/Torque-Converter-Clutch-Predator-Replacement/dp/B07S3TX4C5

And then I see most belts are around 27" long with a ~22cm center-center installed distance between pulleys. It would be sweet to use the engine and gearbox in their current layout, but it's probably the best decision to rearrange everything to use common parts. Is there any easy way to get a brake drum on the gearbox output shaft with the torque converter installed? With this swap I might be losing by drum brake config, so I'll need to figure that out as well

https://www.amazon.com/Adorish-Drive-Replacement-203589-203589A/dp/B08FH3TLMC

 

[ANGELO]

It definitely seems like the best bang for your buck, and it's not that much more then a 212 predator.
A comet brand one is the best. All the cheap ones are probably the same, and pretty much as good for way less. Just upgrade to a comet brand belt.

 

[Skinny]

Just buy a rotted out Samurai, rip the body off, and teach the kids to drive a stick 🤣

Good luck with the build, this will be fun to follow.

 

[WaterH]

Don’t think you will do it for 250 lbs.

 

[AgitatedPancake]

It definitely seems like the best bang for your buck, and it's not that much more then a 212 predator.
A comet brand one is the best. All the cheap ones are probably the same, and pretty much as good for way less. Just upgrade to a comet brand belt.

Yeah totally worth the added cost especially for the convenience of already having the electric start. Cheaper and easier than adding the electric start to a predator. Great note on the belt too, I'll make sure to go name brand there even if I go with an import torque converter

Just buy a rotted out Samurai, rip the body off, and teach the kids to drive a stick 🤣

Good luck with the build, this will be fun to follow.

Haha right. I'm sure they will be driving full sized rigs before too long anyways

Don’t think you will do it for 250 lbs.

I haven't added all of the weights together to have an exact estimate but I do have a few, and it doesn't seem impossible yet. It may be a stretch, but time will tell. The wheel/tire combos I got are 18.5lbs a piece, so 74lbs total there. The engines are around 37lbs, and the reverse gearbox around 12lbs. So that's 123lbs, which leaves another 127lbs for the chassis and axles.

 

[ANGELO]

Also look into the juggernaut or torkzilla drivers. I think they are more a benefit for high rpms but they might help with torque also