New RC Car Land Speed Record

The UK RC Car Speed Championships were held at Shakespeare County Raceway on Saturday and Sunday 12-13th of September and this was a good chance to run the rocket car.

I prepared 4 fuel grains and had a 10lb bottle of NOS standing by for rocket reloads and the body shell was painted up by Ricks Body Shop in Kinver. He did a fantastic job matching the paint on the original Black Knight rocket.

The first run I loaded the accumulator with a small amount of NOS and pressured it up to 950 psi for a short run to check stability. The car went dead straight and the rocket stopped with half the run up still to go so the rocket coasted over the line at 58mph. A perfect 1st run

Next the rocket was reloaded and a full NOS load installed of 12 oz. This time the rocket fired and hesitated for a bit before launching off into full thrust for the complete run up. The rocket stopped right between the timing beams and the run was timed at 117mph for a new UK speed record

Next run was a copy of the 2nd but the rocket didn't warm up so much and I managed 107mph

On the Sunday I had one more fuel grain left so loaded it up for the final run. I drilled out the injector from 1.5mm to 2mm and drilled the exit nozzle out from 8.5mm to 9.5mm. I then connected the accumulator directly to the NOS bottle and loaded it up with 18oz of NOS. I connected the N2 and pressurised the accumulator to 1100 psi and iced it down and re pressurised again

This time we took the car back another 100ft or so and then let it rip for the run. The burn was much better and the acceleration far higher. As the car approached the trap i could see it sliding around so tried shutting it down but the rear brake made the car crab and it flipped just passed the trap

One of the guys read out the speed.....

163.51mph and a new overall world land speed record beating the 161.34 set by Nic Case in 2008...

YES!!

Here is the video

http://www.youtube.com/watch?v=Up6hDcKrH40

Shell

Here is the car and the unpainted shell

The body came out OK. A lick of paint and it will be ready to ROCK!!

I put the rocket engine into a chassis so I could test it out and here are some pics

I then took it to the drag strip to try it out. Here is a video of the test

http://www.northern-radio-moto-club.co.uk/videos/rossajune093.wmv

The car accelerated much faster than I thought and I didnt have time to react to get it straight. I need to sort out the chassis and bodyshell but it was a great test and am looking forward to the event

Cheers

Accumulator test

I have managed to put the accumulator together and carry out a test on the rocket. Here is the setup

• The accumulator piston was moved up to the top so the N2O chamber was as small as possible and the bottom chamber pressurised to 500 Psi
• I applied 500 psi to the bottom chamber with N2 and attached the full N2O bottle to the top chamber.
• The N2O bottle was opened and the pressure in the lower chamber was seen to increase to the N2O pressure of 650 psi
• The pressure in the lower chamber was bled to 0 and this allowed the liquid N2O to decant into the top of the accumulator.
• The top valve was closed and the N2O bottle removed and weighed to ensure it was fully empty
• N2 was applied to the lower chamber and re pressurised to 1100 psi. This returned all the N2O to liquid with no gas
• The rocket was attached and ignited

Here is a video of the test. The main camera didn't work past ignition but it was captured on my mates phone

http://www.youtube.com/watch?v=CoxqtbEjmk8
The results were as follows

Thrust = 12-15lbs
Burn time 12 seconds

The fuel grain was all gone and it was pretty obvious the injector was too big. The next test will be with a smaller injector and maybe 1/2 the N2O

I tested the accumulator today to 2000 psi and it was perfect. Here are a couple of pics

I also managed to calibrate the pressure relief valve to 15oo Psi and also manage to find a small regulator on the net to reduce the input N2 from 1800 psi to 900 psi. I will complete the system next week and test it to measure the thrust and burn time

April 7th update

I found the problem with the rocket. The firework was not generating enough heat in the plastic so was not splitting the N2O properly. I soaked a cardboard tube in oil and inserted it in the rocket, drilled out the nozzle to 8.5mm and increased the injector to 2mm and it worked like a dream. The rocket burnt for 8 seconds on full thrust with half a bottle of N2O. Unfortunately the video camera crapped out so no footage of the test

There was 3mm of polyprop left so maybe I need a bigger diameter rocket. I need to test the rocket for longer to see how long it will burn for

I made an accumulator for the N2O. Basically when the rocket is horizontal gas will be passed to the motor. The accumulator has a sliding piston inside with N2O one side and compressed air or CO2 on the other. The air is pressurised to 1200 psi and when the rocket is fired the pressure will keep the N2O liquid so no gas is passed to the motor allowing a full clean burn. The accumulator will be pressure tested on Saturday April 11th. If its OK I will test the motor soon after.

I'll post some pics later

Failed test

I tested the rocket and here is the video of the test

http://www.youtube.com/watch?v=6zIoVpmVAuw

I am trying to find out what went wrong. I thnk the nozzle throat dia is too small or I am not getting the rocket hot enough to split the NOS. I am waiting for the fuel grain to be drilled out and I'll try again

Cheers