Scratch build electric tethered car racer

[Roog]

On to making the chassis, ok it’s a bit od angle starting with a 16mm diameter hole for the rear axle

rear axle dry fitted

Now I need a slot for the front wheel to poke through, question is where to put it
On to making the chassis, ok it’s a bit od angle starting with a 16mm diameter hole for the rear axle

rear axle dry fitted

Now we need a slot for the front wheel to poke through



Quick check, next to fit the spring and thrust block

 

[WickedFog]

View attachment 180707

View attachment 180706

On to making the chassis, ok it’s a bit od angle starting with a 16mm diameter hole for the rear axle

View attachment 180705


rear axle dry fitted

Now I need a slot for the front wheel to poke through, question is where to put it

One question. I assume you're going to mount the front wheel straight. But since this car will only go around circles, wouldn't it be best to find out the diameter of the track you'll be using this on and angle the front wheel just shy of turning that radius, to eliminate as much tire friction as possible? Would it be better if the front wheel angle were adjustable?

It would actually be kinda fun to test this

 

[Roog]

Ok I’ve assembled the front suspension

And now I am able to fit the fun parts

Next I need to figure out where to locate the battery for best centre of gravity / rotation. But also the receiver, I’m not sure how susceptible it is to electrical noise from the motor or ESC. My plan was to fit it on a bracket suspended over the back axle behind the motor. I would be grateful for your advice on this. Antenna can point up in the supplied plastic tube near by.
I also need to figure out some cable management I’m thinking some small hangman’s brackets screwed in to the top edge of the angle chassis.

So it’s starting to look like a trike at last, Hoorah!

Note: I have left room for a bigger battery

One question. I assume you're going to mount the front wheel straight. But since this car will only go around circles, wouldn't it be best to find out the diameter of the track you'll be using this on and angle the front wheel just shy of turning that radius, to eliminate as much tire friction as possible? Would it be better if the front wheel angle were adjustable?

It would actually be kinda fun to test this

Yes!

I have found the the brass front suspension pivot can be tweaked by fitting shims under the front edge of the flange, this provides very subtle steering

 

[Roog]

One thing I found with my IC car is that if you make something easily adjustable it will adjust all by its self!

 

[WickedFog]

That's looking awesome. Very nicely done.

 

[Roog]

That's looking awesome. Very nicely done.

Thanks @WickedFog i was surprised at how quickly it came together this weekend.

Now I have lots of details to deal with, like tidying those cables is a bit daunting and where to put the on off switch?

 

[WickedFog]

One question. Are your motor mounting slots long enough to allow for swapping to other size pinions in case you want to experiment?

Another thing you may not have thought of, and please excuse the crude drawing, but when you lay your neoprene for the battery tray, leave the internal corner of your chassis exposed. Batteries with sharper corners may interfere in that bottom corner and cause the battery not to rest solid against the backstop.

I see what you mean about your intended Rx location. I would follow through with your idea and see how it goes. I think you will be fine.

 

[Roog]

Cheers @WickedFog excellent suggestion with the foam protection I'll do this.
My motor adjustment is a bit crude, the process was, test the spacing on a separate rig and then copy it on the final chassis, but it didn't turn out as I expected because my test rig had more flex in it than it should, so my first holes make the belt too tight, hence the slots! If I choose to change ratios/pulleys I will probably have to drill more holes, it is a weakness of a crude design.
The question regarding the RX position is more about my lack of experience, I have never experienced and issue with analogue radio / speed controllers and brushed DC motors in the past so I would be surprised if I do have an issue, but I thought I would ask. I am likely to position it so that the antenna has a good position forward of the motor perhaps, either way it can be moved if necessary.

By the way I keep reading your forum I.D. as 'Wickedfrog' which I quite like!

 

[Tunedfrog]

Awesome work and very interesting @Roog . I love the coverage you provide, great photos and explanation of your process
Unfortunately, I have one very serious complaint.
The Wickedfrog statement? That position has already been filled.

 

[WickedFog]

Everyone reads it as WickedFrog at first I think. Which is why my Xbox name is WickedFrog

And Tunedpipe isn't the only frog lover here. I grew up with a nasty swamp (bog for you guys) nearby. We always had frogs to eat

 

[Roog]

Thanks to everyone who has shown an interest and has helped me along the way. I really appreciate it.
I need all the encouragement I can get, car body work is looming.

 

[WickedFog]

Thanks to everyone who has shown an interest and has helped me along the way. I really appreciate it.
I need all the encouragement I can get, car body work is looming.

Wrap a wire hanger around it. Drape a shop towel over it, and pour on the expoxy resin. Done

Although, I've always wanted to play around with clay molds.

 

[Tunedfrog]

Keep it up @Roog we love it.
As far as the body, check out vacuum forming on youtube.
I like WFs suggestion also.
I don't think the Tether car needs to be painted on the inside like the rest of the rigs.

 

[Roog]

Doesn’t look much different but lots of little brackets and holes drilled and finally I have tidy - er wiring, now deciding whether to use the aluminium battery straps or the Velcro ones I have just ordered?

Wrap a wire hanger around it. Drape a shop towel over it, and pour on the expoxy resin. Done

Although, I've always wanted to play around with clay molds.

I am think of making the body using 3/16” thick formers like the bulkheads of an upturned timber boat and skin it in very thin ply, delicate but workable or maybe use it as a plug for a mould.

Surely there are spray on materials you can get these days that you could build up into a skin?

 

[WickedFog]

Doesn’t look much different but lots of little brackets and holes drilled and finally I have tidy - er wiring, now deciding whether to use the aluminium battery straps or the Velcro ones I have just ordered?View attachment 181324View attachment 181325

That looks sooo freakin cool man. I cannot wait to see this run. Are you going to ease into the speed runs multiple times to test it or are you just gonna go for top speed first couple times out?

I like where you put the Rx! Were those two holes atop the rear axle housing meant to be tapped for a mount of some kind?

A little thought about that bracket you have the motor wires ziptied to:
You battery wires are going to need tied down. I was thinking if that bracket were modified, you could incorporate the ziptie mounting holes along with a couple tabs for some decent straps to tie the battery leads down securely (more aerodynamically as well). Like this...

Try to get the connector sitting in the area in green. Add the red tabs by adding a strip of plate aluminum atop that bracket. Then cut notches in the sides of that plate to locate a strap at each end (straps are pink).

Not trying to assume you don't have a kickass way to resolve this in mind already (and curious to know if you do). Your whole design here has been so crazy cool I just cannot look at this thread without my gears turning

AWESOME work man. Machine work, design, layout, enginuity... kudos bro. Absolutely love this, and one of my favorite threads on this forum to date.

Thanks so much for sharing!

Oh... you ever seen panel mount XT60's? You could incorporate one of these into the bracket as well. Would make plugging and unplugging batteries a lot easier.

 

[Roog]

That looks sooo freakin cool man. I cannot wait to see this run. Are you going to ease into the speed runs multiple times to test it or are you just gonna go for top speed first couple times out?

I like where you put the Rx! Were those two holes atop the rear axle housing meant to be tapped for a mount of some kind?

A little thought about that bracket you have the motor wires ziptied to:
You battery wires are going to need tied down. I was thinking if that bracket were modified, you could incorporate the ziptie mounting holes along with a couple tabs for some decent straps to tie the battery leads down securely (more aerodynamically as well). Like this...
View attachment 181326
Try to get the connector sitting in the area in green. Add the red tabs by adding a strip of plate aluminum atop that bracket. Then cut notches in the sides of that plate to locate a strap at each end (straps are pink).

Not trying to assume you don't have a kickass way to resolve this in mind already (and curious to know if you do). Your whole design here has been so crazy cool I just cannot look at this thread without my gears turning

AWESOME work man. Machine work, design, layout, enginuity... kudos bro. Absolutely love this, and one of my favorite threads on this forum to date.

Thanks so much for sharing!

Oh... you ever seen panel mount XT60's? You could incorporate one of these into the bracket as well. Would make plugging and unplugging batteries a lot easier.
View attachment 181327

As ever, thank you for taking an interest and for your helpful experience. As you can probably tell I CADed the main elements and the rest has been free form! I wish I was a better engineer, but alas I get bored very quickly.

The test run is going to be a nerve jangling moment, whilst the others are going to be fuelling up, flicking props trying to breath life into their models I should be able to get on the track quite quickly and give it a spin.

Tactics are bring it up to speed steady then if it’s tracking ok ramp up for full speed. I am worried that the belts I am using might not last long.

Hopefully the weather will improve soon and I can get on the track. I’ll try to get someone to video the big led speed readout as it wizzes past, fingers crossed. Any thing North of 52mph will be a track record and that could easily be beaten by a stock RC car,

@WickedFog I think you are right about tying in the power connector to the strip with the holes, I’d like to keep all wires below that to give some clearance for the future body shell. Not seen the chassis mounted connectors, like so many things in this hobby it’s much more sophisticated than it used to be. I am very limited by my knowledge of what is out there.

I am thinking of my next model, I would like to make one that uses much cheaper parts, that way I might get others to try it and if we can standardise on a chassis we can focus on the gearing and aerodynamic bodywork which is where the hobby should be at, experimenting with car design and not struggling to start the thing!

 

[WickedFog]

As ever, thank you for taking an interest and for your helpful experience. As you can probably tell I CADed the main elements and the rest has been free form! I wish I was a better engineer, but alas I get bored very quickly.

The test run is going to be a nerve jangling moment, whilst the others are going to be fuelling up, flicking props trying to breath life into their models I should be able to get on the track quite quickly and give it a spin.

Tactics are bring it up to speed steady then if it’s tracking ok ramp up for full speed. I am worried that the belts I am using might not last long.

Hopefully the weather will improve soon and I can get on the track. I’ll try to get someone to video the big led speed readout as it wizzes past, fingers crossed. Any thing North of 52mph will be a track record and that could easily be beaten by a stock RC car,

@WickedFog I think you are right about tying in the power connector to the strip with the holes, I’d like to keep all wires below that to give some clearance for the future body shell. Not seen the chassis mounted connectors, like so many things in this hobby it’s much more sophisticated than it used to be. I am very limited by my knowledge of what is out there.

I am thinking of my next model, I would like to make one that uses much cheaper parts, that way I might get others to try it and if we can standardise on a chassis we can focus on the gearing and aerodynamic bodywork which is where the hobby should be at, experimenting with car design and not struggling to start the thing!

52mph should be no problem with your setup I would think.

 

[Roog]

I can’t remember my original calculations (I have them in a folder somewhere) but it pointed at a speed a good way above 100mph.

Better not count my chickens before they hatch.

 

[WickedFog]

I am think of making the body using 3/16” thick formers like the bulkheads of an upturned timber boat and skin it in very thin ply, delicate but workable or maybe use it as a plug for a mould.

Surely there are spray on materials you can get these days that you could build up into a skin?

I missed this.
There is a guy here by the name of @johnnydmd who makes some kickass lexan bodies. Maybe he can point you in the right direction. He even made his own vacuum table to form his bodies.

I can’t remember my original calculations (I have them in a folder somewhere) but it pointed at a speed a good way above 100mph.

Better not count my chickens before they hatch.

I hope you guys have some really solid barracades between you and the cars

I've watched a number of these tethered car vids, and a lot of times, just watching the vids can be a bit unnerving.

 

[Roog]

Yes I’ve seen the vacuum ‘shrink’ frames in action, I know that some use vacuum pack bags to hold carbon fibre and Kevlar in resin to a shape. They would admit that the finish isn’t always the best.

I agree re the videos, the serious racers do go very quickly, to give you an idea of our group, people mill about the outsides of the track whilst others are on a run. I prefer being on the outside of the fence.