My money is on the table too.

Davenz13 wrote:
I like the idea of a temporary roll cage so that with have to enter the mix as well. The axles will provide good fixing points as the don’t turn and are easy to get at.

Apart from the chance of breaking a prop in the case of a rollover, the only real danger is to the cosmetics.  Maybe just tape it over with bubble-wrap for finish protection.

And be sure your pilot wears a hair net or at least a ponytail to avoid her hair getting tangled in the propellers

She does have a full face helmet but getting all that hair in there might be an issue so I  think the first few runs might be in the style of the headless horseman or in this case

the headless pitstop

Well the car has been stripped and the body has gone off to have fuel-proof clear coat applied.

The engine mount has been detailed and engines fitted just to make sure everything fits. I've never been a big fan of self-tapping screws in plastic (tendency to split) and fine threads have a tendency to strip so I put the narcelles in the lathe and carefully turned a groove through the screw mounts, drilled out the holes and fitted nuts to the mounting screws.  



Next phase is making a test bed and running the engines. Slowly getting there.

Well, you know how you’re trying to get something done and life just keeps getting in the way. That’s what seemed to keep happening every time I tried to get back on this little project. This “build a tether car” idea was put forward by Mark (batjac) in September 2015. My, how time flys.  But while dealing with life I’ve been chipping away at it in the background and making some slow progress. I still managed to have a quick peek at the forum every now and then to see what everyone else was up to.
At the last update there were two things to check before an actual run.

1. Test the cars exterior coating against the fuel
2. Run the motors.

The exterior coating versus fuel test
This was done scientifically (I poured fuel all over a similar item and watched result) in a controlled environment (my workshop). Even after several weeks there was no indication of any effect to the exterior coating whatsoever. I’ve reached the conclusion that these car bodies are immune to the effects of the fuel. The first test run will prove this theory either right or wrong.  
I also located two more tin bodies, one of which I’ll use for the initial runs. Don’t have to worry so much now about damaging the car if I have a mishap or my theory about the fuel turns out to be wrong during testing. Never hurts to have a few spares.
The spare bodies have been drilled and all ready for use by just transferring the running gear and engines over.  Red number 09 has been nominated as the initial test car. Seemed fitting since the driver is a mechanic.
 


Running the motors
I needed a test bed to run the engines on and also to see what changes make them run better or worse.
I’ve seen some good ideas and examples of test rigs on the forum here but building one from scratch would just take me too long (it’s taken me nearly two years to get the car this far). I’d seen a Turnigy thrust stand on special from HobbyKing a while back and I thought it was a neat little item so purchased it and put it in the cupboard as one of those “come in handy one day” purchases. Receipt says December 2014, (Wow didn’t realise that much time had passed)
It’s for electric motors but I’m thinking it won’t take much to convert it from testing electric motors to fuel.  



I decided it might be better to have this as a separate post so I'll detail it under "Turnigy thrust stand conversion"  

Well done Dave. Good to see you making some progress.

Now that the engines are tested and running ok I’ve refitted them to the car. It’s ready to run.



Yesterday I bought a 20kg weight to use as an anchor and will make a pin and tether arm to attach to the centre hole of the weight. Once that’s done should be all ready to go.



Finally

You’re cutting it close! Didn’t your driver just finish her last race and retire?

https://abcnews.go.com/Lifestyle/racing-star-danica-patrick-reflects-career-shes-choosing/story?id=55443949

The car looks great!

Thanks,
I’m pleased with how it’s turned out.

The change of driver is absolutely no reflection on Penelope’s driving ability. It was more an owner’s decision on whether the irreplaceable paint finish on the black and yellow No 12 would be damaged by the fuel residue.
Penelope’s agent said she will be seen back in the car at a later date.

Looks good man , bee looking for the run video . It should haul the mail with those twins !!

Progress, progress, progress.

Managed to get a bit more done today. Turned up a flange for the weight centre. The flange goes almost right through the weight. Then turned up a shaft and had a mate tig it into the flange at the bottom. Cut a thread on the shaft and some threads into the weight.



Fitted a pillow mount and bearing and all done.



I have a bit of scrap 3mm aluminium plate which should do to make the tether arm out of. Then off to Hunting and Fishing to get some wire braid for the tether line.
The “Making Lines” post couldn’t have come at a better time.  

Well I’m finally nearing the end. The tether anchor is completed and the tethers are made, one 4.5 metres and one 6.5 metres. That’s including the distance from the centre of the car to the mounting hole and the centre of the anchor to its mounting hole. With the aid of a stopwatch I should be able to work out the speed it achieves. Will try the 4.5m tether first.



First tests will be this Sunday weather permitting. Will video for posting.

Had some 9 volt battery cases from various makers Duracell, etc. Tried all sorts of solvents, paint removers and nothing seems to work. Makes me believe its a non-solvent based ink/paint coating. Probably similar to your finish.

Davenz13 wrote:

Dave your work is amazing.  That tether anchor is a work of art.  My only concern is how the car might react when one engine stops before the other.  I'd hate to see that neat bodywork heading straight for the 20kg weight.  I suppose you have spare bodies, so, trial & error.

Thanks Rod
First run will be with the inner engine and if all goes to plan next run will be with both.
I'm going to take a leaf out of the flying guys book and fuel it so the outer engine quits first and hopefully the inner one will keep the line tight until it quits. The car tracks dead straight when you push it along the ground so it should keep the line taut until it comes to a stop, but best laid plans of mice and men and all that.
Like you say, just have to see what happens when it happens

Most excellent project, just make sure you weigh it down properly.
I once built a ice sled to run on a frozen lake with two 049s and it took off! It wasn't pretty. Be safe brother.

Mark Diedrichs wrote:Most excellent project, just make sure you weigh it down properly.
I once built a ice sled to run on a frozen lake with two 049s and it took off! It wasn't pretty. Be safe brother.

Just check out Dave's picture of his anchor. That puppy's going nowhere outside the circle.

Had to cancel the test runs today
Wet miserable day with relatively high winds

Will try again next Sunday

I love this thread.

Your metal working skills are extraordinary. That engine mount is is a beautiful sculpture in itself. Perfect bends, perfect angles, perfect cuts. A pleasure to the eye. Great work.

Bob

Thank you for your kind words Bob
Hopefully the weather will better this coming Sunday.

Well the weather forecast was bad for today but just after lunch it cleared enough to give it a go. I met my mate at his business premises and after a quick drying off of the surface with a couple of blowers we got down to business.
Tried the 4.5 metre radius tether first to see how it would go.
Hell, the car took off like a scalded cat.          It pulled the tether so tight it lifted the inside wheels about two inches off the ground.  
Once the outside engine quit it started to slow a bit before skidding out on a wet patch. My apologies for the poor focus of the video but it was the first time I’ve used the video option on my Nikon. Even though its blurry you can see it had some pace on.

https://www.youtube.com/watch?v=kSazEMa04pg

Refuelled and tried the 6.5m tether. In my excitement I didn’t turn the camera on but the car completed about a lap and a half before skidding out (sleight rear bias so will add weight to the front) then shot diagonally across the track, snapping the tether snap-link which threw it into several spins before coming to rest against a plastic downpipe. Small dent to front of body and front axle has sleight tweak but all fixable.
It definitely needs the longer tether and once I get the balance right I’ll give it another run. All in all, I’m very happy with it.  

Dave, that was a great run and very fast. I enjoyed it!!!

Man I think the tires must of been smoking after that!