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TAMIYA M-FOUR MINI You asked for it, and here it is, Part 1 of a 2 part review of the new 4WD M-chassis from Tamiya. Tim mortgaged his house and sold his soul to the devil in order to afford to buy one... Tamiya M Four TA05 mini – the 'Oddball Mini'
First impressions:
Removing the kit from the box, you see right away that there are plenty of carbon bits and plenty of blue alloy as well.
This is a well optioned kit with plenty of quality items. It comes with:
*Carbon lower deck
*Carbon upper decks
*Carbon shock towers
*TRF M-chassis shocks
*Blue alloy 5mm hexes
*Universals front and rear
*Alloy motor mounts/bulkheads
*Alloy spur gear plate
*Alloy turnbuckles
*Alloy steering system
*Hi-Torque servo saver
*Front and rear oil filled gear diffs
*Full ball bearings
The instructions are of the usual brilliant Tamiya standard. I encountered no problems at all with the build with everything going together smoothly. There were a few areas where some people might get lost though. The instructions call for shims in certain areas, universals, on the gear diff and on the outer hinge pins … please pay close attention to this. They do need shims but for me I didn’t need 10 shims on the gear diff, 8 was plenty. And between the bearing and the hexes it calls for 2x 0.3mm shims, I needed 1 shim or it was too tight a fit.I could have taken many photos and shown a step by step build but I just wanted to finish it.
So now to the name “oddball” mini. There are 2 big problems with this car. The first is with the supplied 380 sized motor. No mini or touring car uses a 380 motor, the standard has always been for a 540 sized motor, so why have Tamiya gone with the 380? In Australia we run the Hobbywing 13 Turn system, granted it’s technically a 380 sized motor but with the cooling fins on the can it’s actually 540 sized, and the mounting holes are 540 sized. You can see in the photos the size difference between the 380 and 540 sized motors. You can also see that there is no easy way of making a 540 motor fit into this car. If you could somehow machine away the bulkheads you would run out of material … plus the 540 motor would hit on the steering system so it’s just not going to happen. Yes, that’s correct, a 540 motor fitting in this chassis easily - it’s not going to happen!
  For those of you that still don’t want to believe me, the only way to get a 540 motor in this car is to design some new bulkheads which move the motor rearwards by about 5mm. Then the upper decks would need to be redesigned and you would also need different drive belts, if you have a machine shop and a few days spare, then go ahead, but for all intents and purposes it’s not going to happen, the M Four was designed for a 380 and that is how it will remain.
  I now hear you say, well it’s easy, there are plenty of 380 sized brushless motors out there that will bolt straight in … and yes they will bolt in, but, the shaft diameter on a 380 brushless is smaller than the diameter on the 380 brushed supplied with this kit. So the pinion will not fit unless you machined up a small sleeve to go onto the brushless shaft. The Tamiya 380 sized motor has a shaft diameter of 2.25mm, the 540 shaft diameter is 3.1mm, and the green Mamba seen in the photos has a shaft diameter of 1.9mm. The kit is supplied with a 16 tooth pinion and a small brass tube to make up for the difference in size between shaft sizes. I’ve done some checking, and there is one 380 brushless motor with the correct shaft diameter – it’s an 18 turn made by Tamiya, so it is possible to use a brushless system if you really wanted to. I’ve also heard that the Novak Mongoose has a 540 sized shaft in a 380 sized can, if this is true then there won’t be any problems with using normal pinions on the Novak motor. For the Mamba that I had lying around, to adapt the pinion I had to use a piece of antenna tube, it’s crude, but effective.
 
The 2nd problem is the use of the li-fe battery packs. This kit has been specifically designed for li-fe only (sort of like the Manic Street Preachers … sorry, that’s a musical reference). And not just any li-fe, but a special 1100mah “M sized” li-fe.
I thought maybe I could live with the 380 motor, and just tape in a lipo without any problems, again, I was wrong. The gap between the servo and the motor bulkheads is too narrow to fit a standard mini sized lipo in, so the li-fe pack must be shorter and narrower than the lipo. I haven’t seen one up close, but I found the dimensions online:
M size Life - 70 x 38 x20mm
Lipo stick pack (IP3800) - 137 x 46.2 x 24mm
So with no li-fe packs handy, how was I going to get this car running?The only way was to drill an extra hole in the chassis and mount the servo forwards, then run a shorter turnbuckle from the servo to the steering. For clearance I then had to extend the ball stud about 15mm higher than standard. After all this I had just enough gap to slot a lipo in between the servo and the rear diff housing, with only 1 or 2mm clearance from rubbing on the rear tyres. So it is possible to use a standard lipo, but it will alter the handling of the car? I plan to get hold of a li-fe pack soon so I can test the car as nature intended.So why the 380 motor and li-fe pack? Tamiya has also released the RM01 12th scale chassis with a 380 motor, although they were smart enough to design that chassis so you can use either a 540 or a 380.
But again, it’s set up to use li-fe packs.
Perhaps Tamiya have a huge warehouse full of 380 motors and li-fe packs that they can’t sell? Or maybe they’ve decided that the 380 will be the new 540? The 540 sized motors (like a 3.5 turn for example) can put out an amazing amount of power now, too much power for most of us to ever use, maybe it’s time to go back to less power so we can enjoy driving the cars, there will be less wear and tear on the drive train and we’ll get an even longer run time per pack … 30 minute finals anyone? Although with a li-fe pack this wouldn’t be possible.
Our sources in Hong Kong are saying that Tamiya are considering bringing out all of the new Tamiya M-Chassis kits as standard with a 380 … the upcoming M07 could well be the first of the FWD m-chassis cars to come standard with a 380 and li-fe pack, which would also allow for some radical redesigning of the chassis. The future of r/c could be changing … or it could be leading us down a dead end tunnel.
Second opinions: I took the M-Four to one of our recent velodrome meetings to get the opinions of a lot more seasoned racers. Most of them were the same – what no 540? What no lipo? And I think this will be the most common reaction among people who have been racing for more than a few years.
Consider this, if you were new to r/c, you walk into the Hobby Shop and see the M-Four on the shelf, you buy it, then the li-fe pack to go with it, you take it to the track and drive it and enjoy yourself. You wouldn’t be aware of any of the “this motor and this battery don’t fit”, it wouldn’t matter one bit. You just buy your car and your battery and go have fun. If Tamiya have this person in mind then they won’t have any problems selling them. If they would like to sell it to a seasoned racer then they are going to have problems for sure. Change won’t be easy for some.
Testing: currently the weather is 40 degrees Celsius and I’m not really a fan of testing r/c cars in the heat, so you will have to stay tuned to see how it handles!
Current plans are to test it with the standard 380 motor, and then try the Castle Creations Mamba to see how it handles something with a bit more power. Stay tuned!
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