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Old Aug 16, 2014, 07:49 AM
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Laser cut micro car

Don't get excited, so far I'm just thinking about this project. I have a laser cutter and lots of thin plywood and carbon rods in stock. The idea is to make a chassis from plywood and use carbon rod so strengthen it where needed. Carbon rods could also be utilised to give the chassis a simple form of suspension. Alternatively I could laser cut parts from acetal. Only have 2mm and 3mm in stock but thinner is available.

I'd like to have a car small enough to be raced on a table top track. However I also want it to have proportional speed and steering. The "coke can" type cars fit the bill size wise but they are non-proportional. They are suitable as donors for the motor and gears though. I would use a HK-5320 servo for steering and a DelTang receiver. Tyres would be closed cell foam rubber. I have a lathe and mill so making suitable rims is not a problem.

I'm also contemplating a slightly bigger car that would use some A9x9 parts such as the diffs but that is a project that at the back of the queue.
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Old Aug 16, 2014, 08:46 AM
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Gears I will take from an metal gear micro servo. I just took an Emax ES08MA apart and the gears in there are suitable. One of the gears is MOD 0.3 31T which means it will mesh with the 7T pinion from the V911 heli. These gears will be overkill in terms of strength for such a small car. The first couple of gear stages from one of the generic cheap 9 gram servos could probably also be used including the servo motor.
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Old Aug 16, 2014, 11:50 AM
Did you check the FAQ already?
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Interesting idea, wonder what you come up with. You could also use the servo's electronics as speed control, so I've been told.
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Old Aug 16, 2014, 11:56 AM
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I will be watching. Very interested.....
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Old Aug 16, 2014, 12:23 PM
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Here is the layout of the car. I'm in the process of drawing the individual parts. Rear axle will run in ball bearings. I will probably split the chassis in two and join the front and rear parts with carbon strip to give some flex.
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Old Aug 16, 2014, 01:29 PM
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Looks like a nice project but I have to ask, is there any reason why you don't simply buy a dnano? Price?
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Old Aug 16, 2014, 02:32 PM
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Originally Posted by Fixy! View Post
Looks like a nice project but I have to ask, is there any reason why you don't simply buy a dnano? Price?
Until I read your post I had never heard of the dNaNo

I mainly do it because I can. However it will also be somewhat cheaper. If I bought a dNaNo set I would have to add 25% tax on top of the item cost and postage. I'd be looking at $250 for one!

The DelTang RX is the most expensive bit at app. $40. Servos are few $ each and the motor and lipo cell another few $. If I break something I can make spares myself.
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Old Aug 16, 2014, 06:45 PM
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Which receiver are you thinking of using?
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Old Aug 16, 2014, 08:25 PM
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Quote:
Originally Posted by epilot View Post
Until I read your post I had never heard of the dNaNo

I mainly do it because I can. However it will also be somewhat cheaper. If I bought a dNaNo set I would have to add 25% tax on top of the item cost and postage. I'd be looking at $250 for one!

The DelTang RX is the most expensive bit at app. $40. Servos are few $ each and the motor and lipo cell another few $. If I break something I can make spares myself.
I really think that using WL Toys 939 (under $35 RTR) electronics it can be done. The only big issue is to accommodate the bulky servo (19x20x8mm) in such a small place . But this guy at rc-micro.de seems to have solved the problem,










RC Baja Trophy Truck 1:87 scale (4 min 5 sec)


After this amazing lesson of craftmanship at 1/87 scale, take a look at this not so sophisticated 1/64 non proportional die-cast car race.

Micro RC Car Club - NSX, 240Z, MRS (4 min 3 sec)
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Old Aug 17, 2014, 06:41 AM
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Yes dnano are expensive but worth every penny. The mechanic and electronics are amazing and the scale look is just perfect, each model has it's own characteristics and drives differently from the others.
You can tweak things on the esc like virtual inertia(and other usual parameters) to make driving even more realistic for the scale.
The expensive part clearly not worth it is the transmitter.

Anyway I'm always amazed by people building those tiny DIY cars. Do you have any particular scale in mind? 1/48? 1/64? 1/87?
Good luck with your project.
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Old Aug 17, 2014, 06:59 AM
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No particular scale, just adapting it to the size of the components. I really couldn't afford a dNaNo and even if I could it's unlikely that anyone else would buy one to race against me. I'm still trying to get people to buy cheap L939's.......
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Old Aug 18, 2014, 07:37 AM
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Same issue here, people prefer cheap toyish cars over high-end hobby ones
I guess that's the major reason why kyosho doesn't bother marketing them outside of Japan...

Anyway enough off-topic, I'll be watching what you come up with.
What ESC will you use? Did you find one small enough? May be a DIY one?
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Old Aug 18, 2014, 11:46 AM
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The DelTang receiver has a built in ESC:

http://www.deltang.co.uk/rx60b-v61x.htm

I got the gearbox test version done yesterday. Just a quick and dirty setup to ensure the gears mesh correctly. Runs well but metal gears are noisy!

I'm also thinking of making some sort of universal chassis for 1/35 scale vehicles. There are so many to choose from. I used to collect full size Russian miltary vehicles. Don't have them anymore but a 1/35 R/C UAZ 469 would be nice. The chassis should be designed so it's easy to change wheel base and wheel spacing.
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Old Aug 21, 2014, 03:40 PM
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I just took a L939 gearbox apart to see what the ratio is. If I counted right on the number of teeth on the gears, the ratio is 10.31 to 1. On the metal gearbox I made the ratio is 12.18 to 1 so it might have a little less speed but more torque. That's a good thing in my book. I'm actually going to make a version of my gearbox that can be retrofitted on the L939. The L939 has a 3-stage box whereas mine is only 2-stage. Therefore I need CW rotating motors in mine, not CCW like in the L939. They cost peanuts to buy on Ebay so no problem there.

BTW, the L939 is a very hackable little car. Although the RX is not that small it can be squeezed into a smaller car and it should be possible to hook up a smaller servo. Just take the driver board out of the servo and wire the pot straight up to the L939 RX.

Below is a picture of the test gearbox.
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Last edited by epilot; Aug 21, 2014 at 04:17 PM.
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Old Aug 27, 2014, 01:19 PM
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Hi, epilot, your proposal inspired me a few days ago, so I could't help but building mine.

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