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gertman
02-06-2008, 12:27 AM
DTM X-4
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The DTM X-4 is a 1/24-scale 4wd RC car kit. This kit is a little more complicated to assemble because is has A LOT more parts than the DTM-SP. The chassis is made of one pieces of flat 2mm black fiberglass. The most of the rest of the pieces and the upper-deck are made of black nylon. This is a shaft driven 4wd system with ball differentials in the front and rear. The car is fairly rigid with very little suspension. Instead of front u-joints (as in a Micro RS4 and Min-X), keyed axle and hubs are used in the front. The keyed axles work like a ball Allen wrench does on an angle. The motor is mounted high on the chassis directly above the center shaft. The battery pack fits in a holder on one side of the car. Six 1/3 size AAs can be used as a battery pack or one can be purchased from ABC Hobbies. The wheels are made of white plastic with all 4 hubs being machined pieces of aluminum. All four tires are the same width. The bushings that are included with the kit are plastic.

What do you need besides the kit?
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All electronics:
Controller (Radio)
Small Receiver
Micro Servo
VERY Small ESC capable of 6cells (electronic speed controller)
Battery pack (may be purchased separately from ABC Hobbies DIFFERENT THAN THE DTM SP)

AND

Charger (if you have one for your 1/10 scale car your probably already set)
Clear lexan body

Modifications:
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The wheelbase has 3 lengths that can be set. The chassis can accept long motors as found in an Micro RS4. Many spur gear and pinion gears are available. 3 different compounds of foam tires are available. A few different wheel styles are also available. A foam bumper is optional (I would suggest getting one). I would also recommend ball bearings as a worthwhile upgrade. Lots of different bodies are available.

One finial note, I did not have good luck with the electronics ABC hobbies sells to go along with the DTM X-4. Yes it fits BUT the speed controller sucks and glitching was always a problem. Also the servo is hard wired to the combo speed controller receiver. To date I have just ordered some new electronics so I will not recommend any until I have installed them.

gertman
01-07-2009, 09:42 PM
I used to actually race my DTMX4 against HPI Micro RS4's on a 1:10 scale RC track in PA. They have the same size motors, right?

Anyway the biggest problem I had was that the only reciever I could find small enough to fit in the car was AM from the Mini-X and the range was not good enough in the back straight!! Plus it was very hard to see on such a big track.

So, fast forward about 8 or so years and I built my VERY OWN RCP track in my bacement http://mini-zracer.com/forums/attachment.php?attachmentid=24632&d=1208832132
I dug out all my micro RC stuff and started to re-investigate a new reciever. I found a GWS FM reciever that was small enough to fit! YES!!!! Problem solved, or so I thought......

Apparently the NiCd pack was not powerful enough and after 2 or 3 min the voltage would drop low enough that I would start getting horrible glitching. So I next decided I should upgrade the batts.

I ended up with a Thunder Power 730mah/ 7.4V 2 cell pack and now I can run the car for over 1/2 an hour. Problem Solved!!!

OR so I thought.....

gertman
01-07-2009, 09:44 PM
Apparently now I have heat issues because I just burned up my motor :(

I am going to try and get a heatsink to fit on the motor and then probable make a duct in the body.

tinyrc
01-10-2009, 01:59 PM
Gertman, time for your annual post already? :D When are you going to come out to Ann Arbor and race w/ us, plus you can raid our Mini-X parts bin etc.! :)

gertman
01-29-2009, 08:43 PM
I should come out to Ann Arbor, maybe after I get my mini-z awd all fixed up.

gertman
01-29-2009, 08:46 PM
Ok back to the heat issue:

Well, I have decided to attack this issue with a full assualt:

1. Install a heatsink

2. Install a fan

3. Protect my LiPo battary from the heat of the motor; this will also help keep my car from blowing up! :)

gertman
01-29-2009, 09:05 PM
1. Is pretty common sense, a heatsink. Well......I looked high and low on ebay and every site I could think of for micro-RC. I figured a heatsink for the HPI micro RS4 or maybe a mini-z would work. Nope! I could not find a sutable heatsink. So....I stopped by my LHS and brought the car and they were able to help me out. It is not exactly what I wanted because it does not have a flat like the motor does but it would work and it was very cheap, only 3 bucks!! http://www.maxxprod.com/mpi/mpi-29b.html By Mpi MAXX model ACC3921 for a 20mm size motor. Now i had to do some cutting to it and the top deck of the car but it fits.

gertman
01-29-2009, 09:20 PM
2. The next step is to install a fan. I have decided on a Sunon fan 30mmx30mmx6mm. It will fit perfectly in the rear window to draw the hot air out of the vehicle. I think I will use shoe-goo to attach it to the body. This step is not yet complete.

gertman
01-29-2009, 10:06 PM
3. Of course with LiPo batteries one needs to be carefull about heating them up. With the lipo battery I picked and the layout of the ABC DTMX4 the batt is located right below the motor.

Originally I mounted the battery to the chassis with 3M double sided foam tape and did not really consider how close the motor was to the battery. After the motor got so hot it burned up I took another look at the relationship of the battery to the motor.

I found some automotive grade heatshield to stick to the battery but it was way too thick. If it touched the motor the rear suspension would not work correctly AND because the top of the heatshiled is metallic I could really have an explosion on my hands.

I decided I need the precious 2 or 3mm that the 3M foam tape was using and replaced it with the double sided tape ABC Hobby sold to tape the foam tires to the rim. Next I thinned out the heatshield trying to keep as much of the insulation as possible.

Please note that the pictures attached to this post show DTM-X4 with and with out the motor installed AND with out the upper deck installed.

tinyrc
02-01-2009, 11:19 AM
Seriously cool build G! You will bring this and your MA-010 (in whatever condition it's in - we'll get 're fixed up) to our next event - February dates are currently TBD but see http://mini-zdojo.com for details! :)

gertman
03-18-2009, 12:58 PM
I have not updated in a while but I have been working and running my car. Here is the low-down:

I installed the Sunon fan AND with in one lap managed to knock a blade off....oops. Apparently, when I was backing up the body must have deflected and the rear "suspension post" must have hit the fan.

At first I was not 100% sure what broke the fan blade off so this is what I did:
1. I bought a Losi fan with 11 blades designed to cool the spedo in a mini-T. The Sunon fan had 7 blades so I figured this Losi fan looked beefier AND would pull more air.

2. I used a piece of an old foam bumper from a 1:10scale car do fab up a rear bumper inside the body so there would ve very little deflection in a rear end collision.

3. I put a drop of super glue on each side of the fan blade between the blade and the hub.

This fixed my fan durability issue as I have ran the car many more times with out breaking the Losi fan.

gertman
03-18-2009, 01:06 PM
The next hurdle I faced was to actually prove that the fan was helping cool the vehicle.

At first I used a heat gun but have since switched to a thermocouple. Now, unfortunitly I have lots of data but no good conclusions.

I have tried to direct the air flow through the tunnel between the motor and heatsink. I used a water bottle cap to make a shroud and glued it to the inside of the fan. Also I have played around with blocking off part of the fan with some tape. Lastly, I have made a hole for fresh air at the base of the windshield. I will post pictures of everything soon.

I deffinitly need to do more testing with more variations before I can fully conclude that the fan is helping. Me and a friend tried to use smoke to test if the fan was actually powerful enough to draw air in through the hole in the windshield. Unfortunitly it was not. I think that it will be necessary to cut out at least part of the side windows for fresh air intakes.

Right now, my latest test with the fan on after 3min on the track, measured the motor temp at 53degC.

There is one thing that I can conclude at this time, the fan does take alot of battery power and decreases runtime.

tinyrc
03-18-2009, 01:28 PM
pics! pics! pics! (and, dojo! dojo! dojo!) :D

gertman
03-19-2009, 12:02 AM
Enjoy the pics. I labeled them as best as I could.

tinyrc
03-24-2009, 09:56 PM
Looking forward to seeing it in person on Friday! :D ;)