Black Knight: Hybrid Rocket RC Car

A slight technical hitch!

2010-09-16T10:29:00.000-07:00

The 2010 UK speed championships was held on the 11/12th of September and I ran Black Knight on the Saturday afternoon. Here is a pic of the prepared car

Everything went well for the first run and I managed a speed of 151.51mph. Here is a short video. I am waiting for the better one to be delivered

http://www.youtube.com/watch?v=CB_moXZ2DTM

The next run I installed the ignitor in the rocket but it was a different type with no groove in. The groove is to allow the expanding gasses to escape. As the rocket was ignited the gasses built up inside the motor and had nowhere to go so it exploded destroying the car. Here is a pic

I am in the process or rebuilding the car with a few upgrades.

Watch this space

Cheers

Preparing for the 2010 RC Car Speed Championships

2010-07-16T14:39:00.000-07:00

I havent been around for a while but I have been working on the car. The car is basically the same since the last run and I am optimising it for speed. I have installed a new ignition device with a remote relay to fire off the chrge to ignite the rocket. I can now fire the charge from the 3rd servo. I tested this and it works great!

I have fitted a large 3ft X type parachute that is deployed using a small charge of black powder. This has been tested and works good stopping the car almost instantly.

I have tested the car and I managed a speed of 189mph on the radar gun. This shows that that 200mph is in reach with this setup. I will be preparing the car with a fuel load and run up for 200mph for the 2010 UK speed championships on September 11/12th.

Nic Cas is also preparing a car and will be running on August 15th 2010. He is also trying for 200mph. Friday 13th of August might be a good day to try for 200mph!

I have the parts for the upgrade of the Black Knight into the Black arrow. The names are following the UK rocket program of the 1950-60s. The next design uses a 54mm rocket motor 450mm long with 40lbs of thrust for 20 seconds. I will use the original accumulator but fit 2 external N2 tanks feeding the accumulator through a regulator to deliver a steady 750psi through the burn.

The problem for the next rocket is the line of sight. This is overcome by the use of an FPV system. I have ordered a long range system and the idea is to fit a camera on the car and wear video goggles to see out of the car in real time. I will test the system by modifying the car with an electric motor and running the length of the track. The track will be a suitable 2mile runway such as Bruntingthorpe. This is planned for 2011.

I'll post some pics and vids as I get them

Cheers

New RC Car Land Speed Record

2009-09-14T10:26:00.001-07:00

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

2009-09-03T12:42:00.001-07:00

Here is the car and the unpainted shell

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

2009-06-09T07:07:00.000-07:00

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

2009-05-07T06:33:00.001-07:00

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

2009-04-11T09:13:00.000-07:00

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

2009-04-07T13:52:00.000-07:00

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

2009-03-26T13:14:00.000-07:00

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

March 20th Quick update

2009-03-20T00:34:00.000-07:00

After the first rocket test it was obvious that I needed to have a larger fuel grain for a longer burn time. I managed to find a copy of a spreadsheet to help in rocket design and made a rocket motor 41mm dia by 400mm long using the original exit nozzle

By adjusting the injector from 1mm through to 1.75mm I can adjust the thrust from 7.5lbs to 20lbs. All I need to do is test it.

I have made a car (Pics coming) and I fitted the rocket and 800cc NOS bottle and tried testing the rocket but gas from the bottle made its way into the rocket and blew it out. This confirms my original fears that a horizontal bottle wont work in a shaky car. I will need to ensure the NOS is kept in its liquid form by the use of of an N2 pressure system. This means either a small N2 tank and a regulator or a small hydraulic pump. The nos has to be in an accumulator with a sliding piston to keep the pressure medium away from the NOS.

I will post picks of the tests and designs later

So for now all I can do is test the rocket motor on the stand using the bottle in the vertical position until the new pressure system is designed

2009-01-29T10:02:00.001-08:00

Well I have actually progressed with the development and managed to successfully test the rocket motor, well almost...lol. Here is the vid

http://uk.youtube.com/watch?v=qPRg49PmqaM

The rocket is a RATTWORKS H70 motor with the end cut off and the cap drilled out. The injector nozzle was tapped and a 1/8th NPT to 1/4" swagelok fitting inserted and a 1/4" SS liner attached. A 1/4" swagelok valve was attached to a BL351 Futaba servo and this acts as the throttle.
I installed a small firework inside the fuel grain and attached an electric match so I could ignite it with an electric match. The firework was just stuck in place with glue.
The electric match was set off using a 12V battery and allowed to burn for 5 seconds before the valve opened 10%. This allowed the firework to burn away before opening the throttle to 100%
The rocket was at full power for 5.5 seconds before the fuel grain ran out and the flame went through the side of the casing. Here is a pic of the hole it made

The thrust was very strong and blew the grass around some 40ft away from the back of the rocket. Next step will be to make some special fuel grain and a bigger housing.

First basic design

2008-10-27T09:51:00.000-07:00

Here is the first basic design for the car. The NOS tank is 800cc snd the motor produces 5KG of thrust. The servo opens the ball valve so there is a throttle to the thrust. I will add front disk breaks, suspension and a body and that will be basically it. About as simple as an electric car

Project Details

2008-10-26T03:18:00.000-07:00

After building and running a number of IC cars at speed I have deceided to deviate slightly and try to build a non wheel driven car. I was lucky enough to be contacted by Ben Jarvis, one of the few guys in the UK that understands hybrid rocket technology and has the capacity and know how to put together a power system for the car. With his know how of hybrid rocket systems and my understanding of RC technology with regards to speed cars our team has a good chance of building a vehicle capable of 200mph. This car will be called "Black Knight"

The project is in the conception stage and we are actively discussing development and testing. The priority is to design, build and test the hybrid rocket power plant. Below is a picture of a hybrid rocket.

This one is larger than our design but helps explain the basic principle of the system

The tank is filled with NOS and a solid plastic fuel is loaded into the bottom chamber. The solid material is heated and the valve opened to allow the NOS to flow into the bottom chamber. The plastic fuel oxidises and produces the thrust.