1/12 Pancar with 2-cell LiPo and Tamiya RS-380 Sport-Tuned Motor
1. Introduction
When Tamiya released their 1/12 Scale chassis "RM-01" an unusual detail caught my interest. The car featured a 380 sized brushed motor along with a LiFe Battery (6,6V). Shortly thereafter the full option kit was available. The RM-01X. The kit includes an aluminum motor-adapter plate to fit smaller motors (54354). Whereas the Tamiya RS-380 Sport-Tuned motor promises to deliver sufficient power (54393). I liked the idea. Since the required parts are pretty inexpensive I decided put this motor to a test.
Let me start by telling this: It works even better than I had expected. The 380 Sport-Tuned motor with a 2-cell LiPo (7,4V) provides an extremely smooth and controlled feeling. Due to the reduced torque the car accelerates very gentle. If you gear it right the small motor revs up nimbly until it reaches an adequate top speed.
2. Motor
At first I noticed was how light the motor is. With the adapter mounted it puts about 90 grams on the scale. The adapter-plate is milled from aluminum and comes in Tamiya's beautifully blue anodized finish. It offers a transition for two smaller PCD's. Moreover it allows to mount the motor low down within the pod. The 380 Sport-Tuned features a slightly longer shaft that compensates the thickness of the adapter. Along with the motor you'll receive two brass reducing sleeves. These are needed to fit standard pinions.
3. Rollout and Differential
I'm using an Arrowmax Super Diff Gear on my rear axle (AW648068). The smallest available size in 48dp is 68T. It is slightly smaller than the rim. (The next bigger size - 72T - is already a bit taller than D=38mm.) The Super Diff Gears can be equipped with 18 1/8" diff balls. Additionally I fitted a Yokomo thrust bearing (YOK-R12-24TB) and a shorter cone (YOK-YF-24BK). That's my trick to achieve a super smooth operating diff.
Usually I true down new tires to a diameter below 43mm, to gain maximum performance. If possible I run them down to the rim. Depending on track size, grip and driving style the ideal rollout should lie within a range from 28mm to 32mm. I was testing pinions form 15T up to 18T. Most of the time I ended up with 16T (AM348016) and about 30mm rollout.
4. ESC
An old brushed esc had still been laying in my box. The GM-Racing SX 12. Once top-notch but nowadays long-forgotten. A nice side-effect of this constellation is the clean wiring. The two 1,5mm² thick wires (16AWG) could be routed above the pivot ball and below the rear brace. Directly from the motor to the esc. An additional Schottky diode was soldered across the motor terminals.
5. Battery
Nowadays several 2-cell LiPo batteries in 1-cell cases are sold. Basically they are identical to 1-cell 1/12 scale batteries. Internally they are wired as two serial cells and feature a balancer port. The dimensions are 93mm x 47mm x 18,5mm, with capacities from 2900 to 4000mAh and weights from 130 to 160 grams. I was lucky to strike a bargain on the LRP 2-cell 2900mAh LiPo (#430229).
When using a brushed esc without LiPo cut off always keep an eye on runtimes and energy consumption!
6. Track Test
For the first track test I didn't change anything on the setup, apart from adjusting the gearing/rollout. I have to admit that I didn't notice any big differences caused by the loss of weight. Later on I tried all the usual adjustments to accommodate to the track conditions. I raced along with other 1/12 pancars equipped with 1-cell 10,5T brushless systems. The top speed is a bit slower but definitely faster than 1-cell 17,5T. The acceleration out of sharp corners feels very smooth. When running a weaker motor you'll always focus on a setup and driving style that carries as much speed as possible through corners. Entering then next straight the motor will need less effort to rev up and push the car forward.
7. Motor Temperatures
One major drawback of the 380 Sport-Tuned motor is that it runs very hot. Temperatures can reach up to 80°C. Therefore I installed a fan before the second training day. I found a spare fan from an LRP speed controller but it seemed a bit weak. A stronger fan and a mounting position above or in the back of the motor should improve cooling. Considering the low price of the motor it probably can't be wrong to have a replacement at hand.
8. Conclusion
The combination of a 2-cell LiPo and the Tamiya RS-380 Sport-Tuned probably is the cheapest way to run 1/12 scale. It's easy to control and fun to drive. For my taste it reaches a top speed that is sufficient for smaller indoor tracks. When crashing into barriers the lightweight motor might prevent the motor mount from bending. Another side-effect of the lighter car should also be a slight reduction in tire wear.
Disadvantages might be the uncommon battery format, the additional motor adapter and pinions. Particular attention needs to be taken with regards to rollout, motor temperatures, runtime and battery discharge.
quick facts
- about 90 grams less weight
- ideal rollout approximately from 28 to 32mm
- energy consumption with 2-cell LiPo approximately from 1300 to 1600mAh after 8 minutes
- speed should compare to 1-cell 15,5T brushless
- no special setup changes required
Pros
- cheap electronics (esc, motor, battery)
- no voltage booster required
- clean wiring
- easy to drive, smooth acceleration and sufficient top speed
- lighter car, less damage in case of crashes and reduced tire wear
Cons
- motor and pinion adapter required
- smaller pinions necessary to achieve shorter rollout
- high motor temperatures, a fan should be installed
- a replacement motor should be at hand
- it is easy to manipulate a "Silver Can" motor
- cheap entry-level brushless systems might be a better option (2-cell LiPo + 21,5T)
used parts
- Tamiya 54393 RS-380 Sport-Tuned Motor
- Tamiya 54354 Motor Adapter Plate
- (Tamiya 9804535 Pinion-Adapter 2.3mm/3.17mm 5x)
- Arrowmax AM348016 Pinion Gear 48P 16T 7075 hard
- Arrowmax AM348015 Pinion Gear 48P 15T 7075 hard
- brushed esc GM-Racing SX 12
- LRP #430229 - Shorty LCG LiPo - 7,4V - 2900mAh
- Arrowmax AW648068 - Super Diff Gear - 48dp 68T
- Team Associated 6619 - FT Carbide Diff Balls 1/8" 8x
- Yokomo YOK-R12-24TB R12C3 Thrust Bearing
- Yokomo YOK-YF-24BK YRF Aluminum Thrust Belleville Washer & Cone - Black