Autonamous Nitro RC Car Thingy

[djh82uk]

Hi All

Im not sure why I started this project, I was given the car in exchange for an RC helicopter (im not an outside kind if guy so I just have a small indoor size one now)

I realised as the car was also an outdoor thing, and that they were not going for much on ebay due to all the cheapo ones you can get from china etc, I thought I would do something with it.

Im doing it in 2 stages, first I will make all the upgrades that I feel it needs, and then work on the automation part last.

Here is the car:



The big thing on top is the exhaust that I am working on as the original one was broken, it has a cone inside to help keep up the back-pressure as the engine has no valves it needs the back-pressure to keep the fuel in the engine until it has burnt, Also the exhaust tip is threaded so I can try different ones until I get the right pressure.



Today I thought I would make some headlights, I had some cheap chinese 0.75W luxeon led torches lying around, so i cut them up and machined a pair of blocks to hold them:








I really did not think the the workholding through on the mill, as you can see I wasted a lot of material and while I normally use one of the holes to hold it down with a washer/bolt, the holes did not correspond to the T-slots on the bed, so I had to only cut so far and clean them up by hand, of which I did not do a good job as I drew them to be a sort of rounded square.

Any tips on how I should have held these down?  If I did not stop short on the milling they would have got caught by the endmill and ruined the part, aswell as which part of me they hit.

[djh82uk]

Next i think i will work on the Camera mount, finish off the exhaust & start in the electronics, I also need to find a 12v Fish tank pump to prime the engine with fuel so that the car can start itself (originally you had a pipe from the exhaust to the sealed fuel tank, put a finger over the exhaust and the pressure build up would push fuel into the engine)..

DJH

[sbwhart]

Hi DJH

Interesting car that 

I take it you used your CNC mill to shape the lamps, hmmmm interesting, as for clamping it down the easy way would be to use a sacrificial plate. :-


Drill the holes in the job first, where you put the bulbs. Clamp the sacrifice plate to the table then clamp the job to it, with a bolt through the bulb holes, do your milling cutting into the sacrifice plate, job done.

Hope this helps

Stew

[djh82uk]

Hi Stew


Thats normally exactly as I do it (I get through a lot of plate   ), but I messed up my calculations and so the headlamp holes were not in line with the t-slot, and by then it was too late as the mill had already done holes and I am useless at trying to set a job back up as it was, I need to learn how to center/edge fine better me thinks.  I did everything the wrong way on these lamps, im suprised it even worked out, I didn't clamp them down properly, I did not start from home so I had an unknown offset and could not start again very easily.

Think I am just going to use some angle brackets to hold them on, more pics to bore everyone later

DJH

[Divided he ad]

more pics to bore everyone later 

Erm..... Not wanting to sound like uncle Ralph.... but  .... That's why we're all here D    

   needs visual feeding or it can get right out of control     




I'm liking where this beastie is going   




Keep it up 










Ralph.


Oh, and I'm not following the T slots issue very well...... I'm going to have a think of how I would do it.... Pretty sure it's like Stew said.... I might try a C-o-C to show it too....  (others will probably correct me) and see if with the help of others we can pin a good method down 

[Krown Kustoms]

Not boring, anything RC interests me.
I have cars, trucks, buggys, truggys, boats, planes, helis........ of all scales 1/32 - 1/4

As for the light buckets, a plate to screw into on the mill table would work to hold down the work (sacrificial plate) therefore you dont need to worry about the T slot locations.
I use 1 x 6 boards as the plate when I use CNC, if I am cutting all the way through.

[Divided he ad]

I almost went to bed and then remembered this..... it's 01:40 and this is a "best I could"..... Hope it starts a few others thinking and piccy posting!?



 



I know.... The handwriting is terrible!!!   






Ralph.

[djh82uk]

Hi Ralph

Thats kind of how I intended to do it, but the sacrificial plate was only 1/4" thick so the holes needed to go right the way through and into the t-slot, ANd using thick material gets expensive, I don't like wood as it messes up my coolant.

I do need a set of those clamps tho, atm I just drill holes in the plates and bolt them down, causes a lot of wastage.

Thanks

DJH

[djh82uk]

Well I fitted the rear lights today



And the front lights:






One of my next tasks is to find a way to add a reverse gear, Im thinking a motor held via bracket to the underside of the big aluminium plate, with a gear connecting it to  the bog gear in the below pic.  It can also then act as an alternator.

But for it to be a good alternator it would need to be a motor with a low rpm gearbox, or do I go with a powerful drive motor, and fit another motor elsewhere to act as an alternator?




Im also trying to decide upon a path regarding the electronics, Im going to use a Propeller chip for most of the work, and then a GSM modem to receive gps-coardinates to tell it where to go ( i have a few of the modems lying around)

Im fitting a camera but I can't decide wether to have it transmit the signal or to record it locally.  Transmitting will only be short range (compared to the worldwide coverage of the modem) but can have telemetry info overlayed on top of the image.

Again i have no idea why I am making this but as im mostly using stuff I have lying around then it is no big deal, still need to find a cheap 12v fist tank pump tho (or ideas for an alternative?)

DJH

[Divided he ad]

Looking good 


You're sure putting a lot of thought and stuff into this little beastie!!!


The pump idea..... Wouldn't a little oscillator running via the flywheel as a pulley, with a pipe to the inlet and exhaust do?  made of brass/bronze (or other materials)  do the job? there must be someone on here who knows of a simple pump idea??? 



I don't understand a bit of this but I'm still liking the progress pic's 







Ralph.

[sbwhart]

I've probably missed this but why do you need a pump  . Anyway as Ralph suggested a little osilator would do the job as per my lubricator for my loco her http://madmodder.net/index.php?topic=547.255 there used a lot for this type of application if you strip a fish tank pump down thats what you'll probably find.

Hope this helps

Stew

[djh82uk]

The pump is to prime the fuel lines to start the engine, traditionally you would use exhaust pressure by putting you finger over the end of the exhaust, but then it is not able to start itself.

I guess I could look into other types of pump, or try to make one

Thanks

DJH

[bogstandard]

Fish tank pumps usually use a diaphragm of some sort, or rubber type flap valves. These bits are liable to be attacked by the fuel itself and rendered useless.

You would either have to source a pump that uses valves that can resist this type of attack, or go with an all metal pump as Ralph suggests. The easiest way would be to inject directly with say a small syringe directly into the fuel line just before the carb.

Bogs

[djh82uk]

Hmm, I could feed it from the exhaust again, and use a 12v solenoid I have lying around to block the exhaust while it primes.

[Bearcar1]

You might think about utilizing one of those primer bulbs that are used for that very purpose on lawn mowers and leaf blowers. They are only a couple of bucks, very simple to install as well as maintain.

BC1
Jim

[Russel]

Don't most 2 cycle engines on these RC cars have an all position carb with fuel metering on one side and a crankcase pulsation powered fuel pump on the other side?

Russ

[Krown Kustoms]

Most RC nitro engines use exhaust pressure to pressurize the fuel tank. (push fuel from tank rather than pull from tank)
Trimmer, chainsaw, and so on use crank case pulse into the fuel tank for pressure.
-B-

I think a solenoid would work well

[Russel]

I guess it's not hard to tell that I'm familiar with trimmer and chainsaw engines, but not RC engines. Thanks for the clarification.

Russ

[djh82uk]

hmm, overtime in work been keeping me from this, more updates soon

DJH