Thursday, 28 June 2007

Test run at Mallory Park Racetrack

Just back from the track and the test run went OK. The engines were cold and it took me some time to start them but once running I managed a few passes with the capped tyres. After 2 runs up and down the track they were shredded!! Back to the drawing board for the tyres.


I changed to Ennetti 37 shores and they were much better. The handeling at speed was twitchy so I reduced the steering rate to 40% This sorted it out.

We did a speed run about 1/2 throttle and clocked 79mph on the gun!! Not bad for a first run.

After this run I got interference which was the RX pack going flat so charged it up but then the starter box blew up.

All in all a good day. For the next test I intend to change the gearing so that the back lay shaft is 16T and the drive is 18T reducing the gearing to help with the clutch slip.


As I was on my own I didnt manage to get any vid, only a short one of the car going away. Maybe next time

Tuesday, 26 June 2007

High ratio drive

I managed to fix the exhaust that broke last time out. I used a product from the USA called HTS 2000, it worked great.

I finished the high ratio drive on Monday. The rear pulleys were supposed to be 16t / 16t but the belt was too slack so I changed the one on the layshaft to 18T making the ratio even taller. The theroretical top speed is now 194 mph!! LOL. I received the capped tyres from ATS and installed them and I also got the new speed gun!

I started the car on one engine just to check the drive and reved it up on the bench. You could see the tyres expand as the speed increased. I then put it on the ground for a quick spin. Due to the weight and the tall gearing the car struggled to pull off the line and the clutch was slipping so much it started to smoke. When it stopped the heat in the clutch melted the 1st and 2nd pinion gears.

I changed them out and re started all 3 engines. This time the car lept forward and there was minimal clutch slipping.

Another change was I installed 2 x 7.2 volt NIMH 3300 stck packs externally into the TX and changed the TX unit to 40mhz. This allowed me to use a fail safe. The voltage on the TX registered at 16.7 volts and worked perfectly. I just need to see if this effects the range or not

Saturday, 23 June 2007

1st run with new pulleys and belts

We managed to find a nice open car park with nobody in it to test the car and the plan was to run with one engine to loosen the drive train up then do a quick run with three engines to see how it goes.

Here is the video of the run http://www.youtube.com/watch?v=XDlXBxnaELg

As you can see the car was running OK with one engine but what you don't see on the video the jobs worth security guard who came over and told us to bugger off. This was just after running one engine. I decided to ignore him and start all thee engines anyway and do a quick blast.

You can see that the middle exhaust mount comes loose and so we had to abandon the attempt.

Even with the short blast the car had way too much power. The wheels were spinning at the blip of the throttle and this is with the practice engines 2 of which were not run in and all very rich with hardly any power!!

This is OK as the gearing is standard 1/8th gearing with top speed of 65 mph. When the high gearing is installed the wheel spin will be minimal.

The exhaust lugs were only held on with epoxy so i didnt expect them to last. We will re solder them in place and its off to find another car park for a decent test.

Thanks to Jez for the help.

Friday, 22 June 2007

Looks like I have the belt problem solved. Here are a couple of pics of the new belts and pulleys









I disconnected the 2 speeds for engine 2 and 3 and started No 1 engine and drove it around the road outside the house. I gunned it a few times but the turning circle is wider than the road so its a pain to pick it up and point it in the right direction. I'll do a test on all 3 engines tomorrow.

Saturday, 16 June 2007

Update

Hi
I have posted a few pics on other forums of this car but thought I would get everything in one place.
The current world landspeed record for an RC car is currently recognised as 134.4 mph set by Nic Case with a modified Electric TC3 on 30th July 2006. ALl the recent record attempts on the speed record have been with electric cars so I thought I would design and build an IC car to compete with the electric boys.

I have been thinking of a 3 engined car for some time and mulling over the design for a few years and decieded to go with this idea. The original concept was to use 3 x .21 engines and try to use off the shelf items for all the parts of the car to keep down cost and custom engineering.

The target speed for the design is 150 Mph

Here is the first chasis I came up with











The intent was just to work out the bugs of the drivetrain. It was quickly apparent that for a car to travel at a 150 mph it needs a long run up. You also need to be able to see the car and control it. This limited the run up length and so the car also needs to accelerate quickly meaning the car needed to be light

After some thought the chassis was reduced to the one below

The front and rear end are from a Kyosho Evolva 1/8th circuit car. This was to fit with the design intent of using off the shelf parts.

The next job was to fit the engines. I had 3 old engines available that I could use to work out the drivetrain bugs and for a practice run. The plan is to replace these with higher power units when and if needed.



Here is how the engines are linked together.


Next is all the electrics and throttle linkage. This is how it looks before the test run


http://www.youtube.com/watch?v=NnyDXLX0vfw

Above is a small vid of testing the car. We had 3 engines running and the car felt OK but the middle belt stripped again. I have ordered 10mm wide belts with steel re enforcing and new Aluminium pulleys. I will try the car again when they arrive. For now I'll work on the bodyshell

Here is a pic of the body shell. Its an Active Hobbies M-GTR 1/8th GT shell front with a Blitz LOLA rear stuck together and reenforced with carbon fibre rod.


All ready for the sponsors logo!!! LOL...



As you can see i re did the exhausts. I modified 1/8th circuit exhausts so the stinger is 10mm and exits out of the rear. I have been told this will help with high revs and also improve power at the top end where i need it most.
I started one of the engines and was surpriced that the noise level is no more than a normal exhaust. With it straight through I thought it would be much louder! This will please the batty old woman next door.. LOL
Well the new pulleys and belts arrived and as I hadnt modified the layshafts to take the 5mm pitch pulleys I fitted the 2.5mm pitch ones I had ordered previously. As the pulleys were much larger and have more contact area they would be a lot stronger.
I started the one engine and was nice and free with the clutch engaging and spinning the wheels perfectly. A few blips of the throttle and I opened it up for more speed and the belt snapped!!
DAMN!!!!
Thinking it was probably a duff belt I fitted another and tried again. Same again! After a few revs a bit more speed and SNAP! BOTH belts failed!!
After some investigation it dawned on me what was happening. As the speed increases the 2 speed clutch on the layshafts connected to th engines that are off suddenly engages and the gears go from 0-15,000 rpm instantly. This loads up the belts and breaks them.
To run the car with only one engine you have to dissengage the 2 speed on the other engines.
I think the belts are slightly under strength so have decieded to fit the 5mm pitch belts. These take 74lbs load instead of 14lbs. This and only running the car with 3 engines running will solve the belt issue