Scratch build electric tethered car racer

[Roog]

I have been offered some tires, apparently good for 200mph and a loan of a wheel to copy.

Pictures when they arrive.

Is there an emoji for nervous/excited ?

 

[Weezel]

Awesome news!

 

[Roog]

Pictures show a pair of 'lightly used' matched tires (kindly donated to my cause by a kind fellow who runs his cars at the proper Buckminster track in the UK) and a wheel which is on loan for me to copy. The working face of the tire is about 4.5mm wide. overall diameter 89mm.

My next job is to draw up the wheel halves so that I can send them back. Then comes the job of making them and I note a detachable hub onto which the wheel half is fixed. quite a neat design.

Should keep me busy, but unlikely to be ready for next track day :0(

 

[WickedFog]

View attachment 190447View attachment 190448

Pictures show a pair of 'lightly used' matched tires (kindly donated to my cause by a kind fellow who runs his cars at the proper Buckminster track in the UK) and a wheel which is on loan for me to copy. The working face of the tire is about 4.5mm wide. overall diameter 89mm.

My next job is to draw up the wheel halves so that I can send them back. Then comes the job of making them and I note a detachable hub onto which the wheel half is fixed. quite a neat design.

Should keep me busy, but unlikely to be ready for next track day :0(

What does the inner surface of those wheel halves look like?

 

[ahr43]

Hey Roog! Following along on this adventure. Just think how good it will feel when you finally get it right.

Two thumbs up to the mate offering up an assembly for you to copy. What speeds is he getting out of this combo? His tether car is running at a different track? Are the running surfaces similar? Are the tracks surface ground for smooth running? Are tether tracks flat or are they banked? At speed (60mph +), any track imperfection is wont to induce vibration through the tires. Track surface itself could be a factor?

Going now from a 100mm to an 89mm tire? How will that effect your recently revised pulley drive ratio?

[ Edit: Another thought. Are you allowed to change the tether length? Perhaps your car is tethered to a part of the track it doesn't respond well to? If the track is banked, changing tether length will change load on the car and the tires. ]

Great build. Stick with it, you'll get 'er done. -AC

 

[Roog]

What does the inner surface of those wheel halves look like?

Smooth, I am still trying to figure out the dims, if I measure them, then superimpose the CAD drawings of the two half wheels I get a gap at the outer edge of 5.1mm and yet when I do the same to the actual parts it get 4.2mm ! something wrong here. I'd better keep hold of the wheel until I am confident I have it drawn correctly.

 

[WickedFog]

Smooth, I am still trying to figure out the dims, if I measure them, then superimpose the CAD drawings of the two half wheels I get a gap at the outer edge of 5.1mm and yet when I do the same to the actual parts it get 4.2mm ! something wrong here. I'd better keep hold of the wheel until I am confident I have it drawn correctly. View attachment 190453View attachment 190454

The surface with the dykem on it... is it flat or tapered to create a pinch point on the outer lip of the wheel?

Looking at the tire that was clamped between them, there is a ring around the tire where that lip would be that looks like that was a pinch point.

 

[Roog]

Hey Roog! Following along on this adventure. Just think how good it will feel when you finally get it right.

Two thumbs up to the mate offering up an assembly for you to copy. What speeds is he getting out of this combo? His tether car is running at a different track? Are the running surfaces similar? Are the tracks surface ground for smooth running? Are tether tracks flat or are they banked? At speed (60mph +), any track imperfection is wont to induce vibration through the tires. Track surface itself could be a factor?

Going now from a 100mm to an 89mm tire? How will that effect your recently revised pulley drive ratio?

[ Edit: Another thought. Are you allowed to change the tether length? Perhaps your car is tethered to a part of the track it doesn't respond well to? If the track is banked, changing tether length will change load on the car and the tires. ]

Great build. Stick with it, you'll get 'er done. -AC

I am going from 80mm to 89mm dia, but as you say quite a jump. I can only hope that I can hold back the rpm and that it doesn't run out of torque.

The chap who leant me the wheels and donated the tires was running them on an IC car, his car typically get to 160mph I think, I believe he holds the UK speed record in his class. Buckminster is 21m in diameter, it is smoother and faster by design.

The surface of our local track is rough and its diameter 42ft, I am just doing this for fun so if I can get close to 100mph I'll be happy. Despite being invited to try out at Buckminster my car is just a mule for trying out ideas, I would be a bit self conscious turning up with a lump of angle, or as it has been named here: "Freak on a leash".

My heart is in making something that looks more like a vintage 1950's race car, IC or electric I haven't made up my mind yet.

The surface with the dykem on it... is it flat or tapered to create a pinch point on the outer lip of the wheel?

Looking at the tire that was clamped between them, there is a ring around the tire where that lip would be that looks like that was a pinch point.

I'll send a pic in a min, my phone has decided to do an update!

The wheel parts look parallel, the tire running surface is 4.15mm wide and the width at the root before the inner retained ring is 5.39mm, so the tire tapers from the root to the outer edge. the inner ring is 7.6mm wide so quite a bit to grip onto.

As I see it the wheel will grip the root.

I have some remeasuring to do!

 

[WickedFog]

That's really strange. Do you have a height gage and a surface plate?

 

[ahr43]

"lump of angle." "Freak on a Leash." Gotta love the UK way with words and phrases.

Buckminster is half again the diameter of your track and smoother. Perhaps once you get your mule sorted, you can get the 'ton' there as a provisional or 'guest' runner? Running the 'ton' at your track would be even better.

Like the idea of building to an old school speed runner. Good luck. Cheers, mate. -AC

 

[WickedFog]

I guess the wheel at least has a recess in it to contain the raised area of the tire, preventing it from coming out of the wheel. But I don't understand why that outer lip on the wheel isn't tapered to match the tire, or even better, tapered more so the the outer most surface of the wheel is pinching the tire. Id make the outer gap of the wheels pinch the tire by about a mm or so myself, and those surfaces would definitely be tapered to do just that.

Just curious... how fast is the guy going that uses this setup?

 

[Roog]

That's really strange. Do you have a height gage and a surface plate?
View attachment 190456

Hi @WickedFog sadly I don't, it would be nice!

"lump of angle." "Freak on a Leash." Gotta love the UK way with words and phrases.

Buckminster is half again the diameter of your track and smoother. Perhaps once you get your mule sorted, you can get the 'ton' there as a provisional or 'guest' runner? Running the 'ton' at your track would be even better.

Like the idea of building to an old school speed runner. Good luck. Cheers, mate. -AC

"Freak on a Leash." was from your side of the pond, the "lump of angle" mine! Cultured I am not! :0)


Yes lets see how fast it can go if the wheel stay on, my 30T pully turned up today so I will have a new gear ratio of 3:4 compared to the previous 1:2, I am hoping this will be friendlier to the belt at the motor end.

Yes I like the idea of building 'a car' and it isn't all about the speed at our track is really is about everyone having a go.

I guess the wheel at least has a recess in it to contain the raised area of the tire, preventing it from coming out of the wheel. But I don't understand why that outer lip on the wheel isn't tapered to match the tire, or even better, tapered more so the the outer most surface of the wheel is pinching the tire. Id make the outer gap of the wheels pinch the tire by about a mm or so myself, and those surfaces would definitely be tapered to do just that.

Just curious... how fast is the guy going that uses this setup?

I will check the wheel halves out using a scriber stand to compare points. I think the inner ring of rubber is the main anchor for the rubber.

I think his IC cars are travelling at around 160 mph, but that is on a larger diameter track.

 

[WickedFog]

I think his IC cars are travelling at around 160 mph, but that is on a larger diameter track.

Oh hell. You should be golden then I would think.

 

[Roog]

Oh hell. You should be golden then I would think.

It seems he runs the real thing, his models look very smart 3.5, 5 and 10cc on tuned pipes.
Big money too, he tells me that he gets his parts when attending competitions in mainland Europe

I do hope these tires work, it would be good to concentrate on other factors, which include me working on my aging motor home which is in need of repairs!

 

[Roog]

Hey Roog! Following along on this adventure. Just think how good it will feel when you finally get it right.

[ Edit: Another thought. Are you allowed to change the tether length? Perhaps your car is tethered to a part of the track it doesn't respond well to? If the track is banked, changing tether length will change load on the car and the tires. ]

You raise a good point @ahr43 the tethers are made up and tested, the heavy duty one that I have ‘been assigned’ is slightly longer which means that my car runs right at the edge of the track where it isn’t quite so smooth, I can’t change the tether length but I might shorten the tether connection bar which forms a part of my car to bring it into the track a little. (About an inch).

The track is quite a narrow donut of concrete so there isn’t much scope for running on a different length of tether.

I have measured and re-measured the wheel I was loaned so now need to make a start on my new racing wheels,
The bar I have to make the wheel out of is 3 1/4” in diameter, I suspect it’s going to be tough going for my lathe. I’m not looking forward to parting off!

 

[Roog]

I’m back on the lathe making wheels and losing the will to live, and to make matters worse my lathe is maxed out with the size of the bar stock, here it is gingerly facing off.

Having trouble loading images but they have attached in order.

Then I had fun playing with the ‘bolt circle function’ on my mill DRO, this turned out a lot better than I expected, and once centred allows you to dial in holes located at equal pitch on a circle with a second set off set by 30 degrees! Brilliant stuff :0) I just need it to tap all those holes now.

And on to turning the profile

After an afternoon in my shed I have half a wheel, half finished!

Nearly killed me hacksawing 3 1/4” diameter bar, I need a power hacksaw.

 

[WickedFog]

You need you a bandsaw. That would really suck hacking through that much aluminum.

Wheel looks great. What did you figure out on your measurements being off?

 

[Chubaka]

I hope you turned the lathe on while hack sawing it. Can't wait to see the final project.

 

[WickedFog]

I hope you turned the lathe on while hack sawing it. Can't wait to see the final project.

Oh wow. That would have been a good idear.

 

[Roog]

You need you a bandsaw. That would really suck hacking through that much aluminum.

Wheel looks great. What did you figure out on your measurements being off?

Definitely need something because parting off wheels 80mm in diameter is not happening, poor lathe isn’t rigid or powerful enough. I know I need a bigger lathe!

Actually a horizontal band saw will probably do,

The dimension error was corrected and a useful check was to put the two wheel halves together and measure the gap without a tire fitted.

Some progress today, now I have two half wheels, mostly complete.