26 July 2007
It's hard to find a good quality low-profile servo to steer some of our smaller cars (like an M-chassis or a cramped electric tourer).
Futaba makes one and now KO Propo makes one, but these cost more than the car I intended to put them into, so I looked around for a
cheaper alternative and found the Bluebird BMS-705MG. It has metal gears, a decent amount of torque, a respectable speed, is analog
and costs a fraction (a quarter to be exact) of what the Futaba costs. Since I was already paying for shipping, I bought two.
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The servo really is very short, but I found that it's a bit wider than normal servos, so on my M-chassis, I had to make some new servo mounts to fit it. Also, to my disappointment, I have not found a single touring car that it can fit in. The one in my M-03 Mini Cooper stripped a gear, but to be fair, I had a good amount of crashing in the car and by the time I realised the servo had stripped, my chassis was also cracked and my steering rod was bent as well. |
| Here it is in the DF-03. I had to mod the chassis a little, but the servo fit very well after that. Read more about the mods on my DF-03 page here. |
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Some specs I dug up on the internet to compare low profile servos.
| Servo | Dimensions | Weight | Torque (4.8V) | Speed (4.8V) | Torque (6V) | Speed (6V) | Signals |
| Futaba S9550 | 41X20X25mm | 45 g | 4.8 kg/cm | 0.14 s | 8.5 kg/cm | 0.11 s | Digital |
| Futaba S9551 | 41X20X25mm | 45 g | 6.6 kg/cm | 0.14 s | 9.8 kg/cm | 0.12 s | Digital |
| KO Propo PDS 2413 | 41X20X25mm | 45 g | 8.5 kg/cm | 0.10 s | Digital | ||
| Bluebird BMS-706MG | 43X22X22mm | 35 g | 4.6 kg/cm | 0.18 s | 6.0 kg/cm | 0.13 s | Analog |
Conclusion: It's a decent servo for the price but beware of the extra width, which might make it difficult if not impossible to fit in some cars.