Scratch build Nitro tethered car

[Roog]

That may be better. Anything to account for the scrub the inside tire is getting. Though it's probably not enough to even worry about.

Introducing an LSD would require a fair bit of redesign, probably for the next car.
I hope to visit 'Buckminster' this year where there is a proper circuit and their meets have a greater gathering of experienced builders. I hope to learn from that.

https://www.onthewire.co.uk/buckmter.htm

Its the thin circle near the bottom of the site

 

[tudordewolf]

Instead of a diff, just offset the wheel diameters by the right amount. Not like it ever needs to go straight or turn the other way. Could have a few different wheels on hand to account for different track diameters.

I'm curious to see how a more recent nitro engine would do in a tether car, running a turbo plug and 30% nitro, revving past 30k rpm. Would also resolve the clutch & flywheel issues.

 

[Weezel]

I wonder how well a belt drive would work out. You could get urethane o-rings in all different sizes. Then you wouldn't be confined to a set center to center distance of gears.

Would lose efficiency but make mounting components easier if they held up.

 

[Roog]

I ran my new rear tires today at the track, really smooth, it was looking promising,…..

I brought the car to a halt on two wheels, just as the photo shows, no drama.

I got it up to 65mph, with more throttle to go, (a new track record!) then there was a brief noise and we saw the tire fly off into the hedges. There was no hope of finding it, I just hope the sheep in the field don’t either.

 

[Roog]

Nice! It turned one tire invisible?

Well come on man. You simply can't just post that pic and not fill us in. Do you even realize how long we've been waiting for another run? I am emailing Santa and telling him to put you on his naughty list for not sharing!

Hope nothing bad happened.

Sorry I have edited it since your message.

I think the tire split, because it came off in one piece and I'm fairly sure that it didn’t just roll off the rim.

I continued to run using my previous surviving home made tire and wheel. We noticed that the car would make a strange rumbling noise at around 60mph, perhaps it’s a belt resonance? One suggestion is to get a new motor pulley of a larger diameter to put the belt through a less tight bend, another thought is whether the motor is cogging I.e. the rotor can’t keep up with the rotating magnetic field?

Is this a thing with brushless motors?

 

[WickedFog]

One suggestion is to get a new motor pulley of a larger diameter to put the belt through a less tight bend,

You might want to get some delrin or nylon (self lubricating) and make that belt guide like I showed you earlier in this thread. You might even add external guides. It very well could be the tight radius of the motor pulley causing belt flutter. If you can get the pulleys closer to the same diameter, that may resolve some of that. Have you not ran it up to speed on a bench to see what issues you may have?

another thought is whether the motor is cogging I.e. the rotor can’t keep up with the rotating magnetic field?

Is this a thing with brushless motors?

Not after getting past the initial startup, no. You could try a sensored setup if you can't figure out any other causes. But I don't think it's the motor.

As for your tire flying off, i was afraid of that. You're going to have to bite the bullet and encompass those tires into a reverse cone shape with your wheels. If it were me, I'd only leave about a centimeter of the tire exposed. The rest would be encapsulated in an aluminum housing.

Oh, you posted this in the wrong thread

 

[Roog]

I wonder how well a belt drive would work out. You could get urethane o-rings in all different sizes. Then you wouldn't be confined to a set center to center distance of gears.

Would lose efficiency but make mounting components easier if they held up.

Not sure @Weezel I have used o-rings as drive belts in the past, I had a tiny Unimat 3 lathe and it ate O-rings. What would happen is that a tiny fleck of metal or grit would get on the ‘belt’ and slowly ease its way into the surface then the belt tear right through very quickly.

You might want to get some delrin or nylon (self lubricating) and make that belt guide like I showed you earlier in this thread. You might even add external guides. It very well could be the tight radius of the motor pulley causing belt flutter. If you can get the pulleys closer to the same diameter, that may resolve some of that. Have you not ran it up to speed on a bench to see what issues you may have?

Not after getting past the initial startup, no. You could try a sensored setup if you can't figure out any other causes. But I don't think it's the motor.

As for your tire flying off, i was afraid of that. You're going to have to bite the bullet and encompass those tires into a reverse cone shape with your wheels. If it were me, I'd only leave about a centimeter of the tire exposed. The rest would be encapsulated in an aluminum housing.

Oh, you posted this in the wrong thread

Ha ha, so I did, old age!

You might want to get some delrin or nylon (self lubricating) and make that belt guide like I showed you earlier in this thread. You might even add external guides. It very well could be the tight radius of the motor pulley causing belt flutter. If you can get the pulleys closer to the same diameter, that may resolve some of that. Have you not ran it up to speed on a bench to see what issues you may have?

Not after getting past the initial startup, no. You could try a sensored setup if you can't figure out any other causes. But I don't think it's the motor.

As for your tire flying off, i was afraid of that. You're going to have to bite the bullet and encompass those tires into a reverse cone shape with your wheels. If it were me, I'd only leave about a centimeter of the tire exposed. The rest would be encapsulated in an aluminum housing.

Oh, you posted this in the wrong thread

Thanks for your thoughts on motors, I suspect the belt myself.
Funny thing is I followed the advised tire fixing to the letter.

I have another plan for the conveyor belt tires but it involves making new hubs and much working of the rubber.

 

[Weezel]

As for your tire flying off, i was afraid of that. You're going to have to bite the bullet and encompass those tires into a reverse cone shape with your wheels. If it were me, I'd only leave about a centimeter of the tire exposed. The rest would be encapsulated in an aluminum housing.

I agree. Or you might need to break down and get some tires that can handle those speeds. Centrifugal force is your enemy and the more mass your tires have the more they want to blow apart.

Not sure @Weezel I have used o-rings as drive belts in the past, I had a tiny Unimat 3 lathe and it ate O-rings. What would happen is that a tiny fleck of metal or grit would get on the ‘belt’ and slowly ease its way into the surface then the belt tear right through very quickly.

I was thinking as a single use (or disposable) item on your nitro build. Just an idea thrown out there. Didn't know how much time and effort (and money) you wanted to spend on it since you mentioned using an engine and gears that where laying around.

I have another plan for the conveyor belt tires but it involves making new hubs and much working of the rubber.

I hope it works out but I think it's going to be a fruitless endeavor.

 

[Roog]

One suggestion I had at the track today regarding the geared output of the nitro flywheel is to grind the small gear off and cut a key way to use it to drive a shaft.

Oddly it would be akin to many retro car designs I have seen and it would work with a geared rear axle I have already. I am trying to keep this hobby fun and low cost.

Not too bothered about going fastest, I’d like to make a scale body shell for this one may be even a traditional ladder chassis too.

 

[Weezel]

I'm following along because your builds look like fun!