Motorcycle Powered Kart: Father Daughter Project

[Dale]

Speedway Motors sells a cheap notch cutter for tube also.

A notch cutter would be neater than my grinding! Not a bad idea actually. You can never have enough tools right?

Bit of restoration:

Took the steering rack apart, cleaned it up , lubricated and fresh paint.
No play on it.
The guy had 3, and they were all kinda "siezed" - you could tell it was just gunk in there, and with no leverage it wasn't possible to turn it when I bought it, but its turned out great.

• Im using the Quad's Steering arms.
• Will have to shorten them.
• I'll have to make up a linkage between the steering rack and the steering arms, as the VW's steering arms have a completely different system to the light weight ATVs system.

• The steering shaft is too long, and will have to be shortened.

This got me thinking that I should make an adjustable column, so as "A" gets bigger, we can adjust it accordingly.
Something like this maybe: Tube with ID matching the shafts OD.

For the shifter, something like this:

And the pedals I was thinking Ill make up a kind of a pedal box that will house everything.
Im just not 100% sure on the best way to spring tension the pedals.
That needs some thought.

Another days wok done!

 

[Dale]

Ill be doing a CAD update on the new frame design sometime this week, and will post it up.

 

[Dale]

Frame Design Update

This is what we've currently built (weight 12kg):

Adding in (Green) to make the central "chassis" rigid:

 

[farmer92]

Why not run a support over the top? it would serve both to stiffen the frame, and as roll over protection.
Unless you really want the open cockpit, in which case carry on, but an overhead support would be a lot better at preventing the middle of the frame from sagging.

 

[Dale]

Yeah I really do want to try and keep this thing open cockpit as you say.

 

[Eleganten]

Why not move the supports up? Would create a better support but still keeping it open at the top. Look at the frame of an Ariel atom.


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[DohcBikes]

Why not move the supports up? Would create a better support but still keeping it open at the top. Look at the frame of an Ariel atom.


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Bingo. It actually will be stronger because you can directly tie the front to the rear with no frame rail sandwiched between them. Ingress will be affected but not dramatically

 

[Dale]

Why not run a support over the top? it would serve both to stiffen the frame, and as roll over protection.
Unless you really want the open cockpit, in which case carry on, but an overhead support would be a lot better at preventing the middle of the frame from sagging.

Why not move the supports up? Would create a better support but still keeping it open at the top. Look at the frame of an Ariel atom.

Bingo. It actually will be stronger because you can directly tie the front to the rear with no frame rail sandwiched between them. Ingress will be affected but not dramatically

Good discussion. :-D As far as I can tell, youre all kinda saying the same thing?

Im not convinced that by moving the parallel set of tubing currently under the car to a position higher up will make that much of a difference?
Is this what youre suggesting? :

The Atoms frame wraps around the vehicle. Its much cooler no doubt. Also bear in mind the Atom is WAY bigger than this little kart. 3.4m vs 2.2m in length and 1.8m vs 1.4m in width.

Right now Im trying to make a simple central "chassis".
Heres two more views of where my heads been at:

The reason I went "under" the car with the reinforcing is because by going on top, the seats are then 80mm higher. Thats a big deal for me, because Im trying to get this thing as low as I can get it.

Im totally open to changing things up and making this better where I can, so Im hearing you guys!
I mean, look how cool this:

So, maybe this IS the way to go.

• Downside for me is that it might require more material (weight), and will be more complicated to build. Maybe not.
• Upside is, its WAY cooler looking, and Ill be building something much more ambitious and challenging.
• Reality is, this is a kart for my 8 year old daughter

So, lots to think about.
Thanks for keeping me on my toes, and pushing to make this as good, if not better than I imagined it to be.

 

[Dale]

PEDALS

Starting getting my head around this item.
Took measurements off the cables, and then added 10% for stretch etc.

Cable distance needed to travel:

• Accelerator: 40mm
• Clutch: 22mm
• Brakes: 40 mm

This is the VW's Pedals. They are designed to hang from under the dash.
By doing a couple of mods to them, seems they could work nicely, flipping the pedals around, and mounting them to the floor.
160mm of travel makes for 40mm of cable distance at those positions, which Im guessing, seems pretty reasonable and comfortable.
Will be doing some tests with "A"'s feet soon

 

[irk miller]

Ever looked at kart chassis? It's crazy how flat they are.

 

[Tune-A-Fish]

Side impact is always a good idea... Air bags? ;D

I love this thing and when I get caught up I'm gonna attempt a single seater much like this.

 

[Letze]

Deviant, part of circle track and super kart design is chassis flex, they're actually designed to lift the inside rear wheel when turning. this is necessary to counter the under steer presented with the solid rear axle. The same thing happens on an ATV with a solid axle but under different circumstances, normally with the chassis rolling towards the outside letting the inside front and rear rise. Since the front is sprung it maintains it's connection with the ground, but the inside rear will rise as it shares its suspension point with the outside.

I'm curious to see the solution Dale come sup with.

 

[DohcBikes]

Good discussion. :-D As far as I can tell, youre all kinda saying the same thing?

No, but a couple of us are.

The atom frame is designed for a heavier car with a much more powerful engine. A design such as this would be overkill, therefore detrimental to performance.

Yes, your revised drawing shows the basic concept of what needs to happen imho. In the previous configuration, there are still 2 points that are going to recieve a large amount of load at times. The revision does a much better job of distributing the load throughout the chassis, because it is directly tied to more of the existing design.

 

[el barto]

This is awesome.

 

[Dale]

Ever looked at kart chassis? It's crazy how flat they are.

Thats a pretty badass looking kart chassis. Never seen one with this front extension / or is it the front wheels pushed further back design. ?

I love this thing and when I get caught up I'm gonna attempt a single seater much like this.

Nothing less than 600cc with discs and suspension all round OK!!??

Deviant, part of circle track and super kart design is chassis flex, they're actually designed to lift the inside rear wheel when turning. this is necessary to counter the under steer presented with the solid rear axle. The same thing happens on an ATV with a solid axle but under different circumstances, normally with the chassis rolling towards the outside letting the inside front and rear rise. Since the front is sprung it maintains it's connection with the ground, but the inside rear will rise as it shares its suspension point with the outside.

I'm curious to see the solution Dale come sup with.

When I first started thinking about how to do this project, I was going use a golf cart chassis as the donor.
Its got pretty much everything you need.
Steering system, suspension all round, diff, linear torque etc.
Downside for me was the cost of batteries, charger and new electric motor, the general size of the golf cart felt a little small to me as well.

... and if you thought an electric motor couldn't be sexy, check out Rimac's Supercar electric motor:

http://www.rimac-automobili.com/en/


Getting back to the Diff - man, this is a tricky one!

Im not sure how the motors drive shaft can be connected convincingly to a diff, and also, that way, you're cutting out chain drive and taking sprockets out of the equation... Unless Im missing something here? Any ideas / thoughts?

I was just going to make a 31.75 mm tube axle, running in a couple of self aligning bearing units, with a sprocket.

But you've got me thinking! Dang!

No, but a couple of us are.

The atom frame is designed for a heavier car with a much more powerful engine. A design such as this would be overkill, therefore detrimental to performance.

Yes, your revised drawing shows the basic concept of what needs to happen imho. In the previous configuration, there are still 2 points that are going to recieve a large amount of load at times. The revision does a much better job of distributing the load throughout the chassis, because it is directly tied to more of the existing design.

Gotcha!

This is awesome.

Thanks buddy! This is turning out to be a lot of fun!

 

[Dale]

Controls

Took measurements today!

The seat rails have 200mm of movement. This was the starting point.

In these designs, the steering shaft can be adjusted by 100mm.
The thin green line in the front is the axis point for the pedals.


I generally leave pieces of paper lying around where I sketch out ideas, and try to solve problems.
"A" has a slightly older brother, who often hijacks my notes. This one had me laughing today :-D

 

[Tune-A-Fish]

Triumph GT6 IDS rear Diff: I plan to use two for my crawler with a Suzuki LJ80 trans/transfer case.

 

[farmer92]

What is the height difference between the extra rails you added under the frame and the original ones?
What if you ran them right about the height of the upper front suspension arm?
It looks like it would about double the distance between the two and would double the strength that these members would contribute. Plus the benefit of side impact protection.
It would not contribute to a significant weight increase either, and it would still leave the top open, kind of like a berrien sandrail but without the roll cage.

 

[Nj732port]

I love when this thread has updates ;D

 

[jpmobius]

Some very good points made regarding the frame and especially (lack of) differential. Evidently not incorporating one in the original application worked just fine, but I would expect the larger size, greater weight and vastly better traction in a pavement application would all conspire to make a lot of trouble with a solid axle. Anyone familiar with trying to roll around a solid axle drag car can verify that even fairly small turns in small distances are literally impossible without picking up the rear axle with a floor jack. The engine can easily overcome this problem but often as not such a setup will simply slide the front tires straight ahead (pretty much 100% understeer!) rather than loose the grip from one of the rear tires. Of course you are not making a dragster, but my money says this will be a problem, not merely a nuisance. You could simply drive only one of the rear wheels which would eliminate the problem, but if you have a notion to make this vehicle more powerful down the road you will again be looking for some form of final drive that drives both wheels. My guess is that, with the size, weight, and Hp you look to be heading toward, the lame sounding one wheel drive would work just great.

Nice explanation for the carts. Since carts have NO suspension at all, at least in the way of springs, shocks and links, they have to be pretty bendy just to keep all four wheels on the ground, and with the noted understeer problems the ridiculously simple looking machine gets quite a bit more complex to engineer. In any event, aside from the solid axle, they aren't much of a model for your project. Despite the general concept of keeping the mass as low, central and minimal as possible, it is always a trade-off with other demands like practical construction, practical materials and safety issues. For example, adding structure at "window sill" height will add weight, and it will be high rather than low, and it will be far outboard rather than centralized. However, structure in such a location can be VASTLY lighter for the same structural strength as say structure low and close to the center, and offer the obvious safety benefits to boot. Look at it like this when deciding: If you need x amount of stiffening to get the chassis to function, that will come with the price tag of added weight. Let's say you can add the stiffness you need with some high and wide elements at "window sill" height which will weigh z Kg. You don't like the outboard location for whatever reason (increased moment, lack of easy ingress, lack of cool looks, etc.) so you calculate it will take 4z (or 6 or 8z)Kg to provide the same stiffness in a more desirable location. So what is the solution? Make the car too heavy, so it performs poorly, make it too flexible so it handles badly, or make it light and stiff but otherwise unattractive or hard to get into so you don't want to drive it? Obviously, at the end you just have to pick your poison and commit to a plan of action, but in the main, most of the time you simply end up doing your best to chase away the biggest evils and hoping for the best at the end. Sacrifice a bit of stiffness and safety for low weight and likability. Making the best trade offs often results in what turns out to be the best engineering.