Unreliable Servo o11 (Hub Mount) Bit

Hi helpful makers,

My employer and I have been running a number of hands-on children’s school holiday robotics workshops using the LittleBits STEAM class sets. We’ve had a lot of success using the LittleBits kits despite one particularly difficult bit: the Servo o11 Hub Mount bit. Although we’ve only held around 10 workshops we’ve already found ourselves needing to replace this bit twice due to it becoming faulty. After a few uses, rather than turning as it is supposed to (appropriate to the robotic arm challenge), the bit merely vibrates or turns with a lot of jarring.

I have suspicion to believe that this faulty bit has been updated from what we have been using currently (see here: https://littlebits.com/products/servo) to the newer cross axle bit (https://littlebits.com/products/cross-axle-servo). If so, can anyone confirm if the axle bit is compatible with the other bits from the STEAM student kit?

My electrical engineer boss hasn’t had any luck with adjusting this fault so if you have any advice before we pour more money into replacing an unreliable bit, that would be hugely appreciated.


Ah children. Don’t you just love them. They derive such pleasure from little things, like driving the servo to the end stop and waiting to see what breaks first, the gears or the servo coil.

With plastic geared servos, it’s usually the gears. With metal geared servos, the coil, but it takes a while.

I don’t know how the horn is attached to the cross axle servo. So I don’t know if it can be removed to fit the same horns as the standard servo. Also, is the cross axle servo continuous rotation?

If you are not using the servo to drive anything, and just to demonstrate how a servo works, it won’t matter which servo you use. The price of the two is the same, so I would expect the same quality.

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I have a suspicion that the servo may be the same just with different connectors to make it compatible with some of the newer littlebit kits. I’m basing this the price and the face they both appear to be using the same control board. My guess is that the students are probably a little too rough for the servos and they can’t take the punishment.

You or your boss may be able to replace the servo with something a little more robust, or even more replaceable.

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I looked at the images for each of the LittleBit’s servos, and they do use the same servo, a Batan B1122. So switching to the cross axle servo probably won’t help, but you could probably source the servos themselves, for less than the complete LittleBits part, and replace the damaged servo.


Hi - my son received the droid maker kit and managed to put it all together, and get it going. Loved it. However, the same part (servo) has the EXACT issue you’re talking about - occasionally it will spin the shaft, but there’s clicking and whirring, and then there’s just vibration and the shaft doesn’t spin. Put any load on the shaft and it won’t spin.

How can I get a replacement? It seems unfair that this piece only lasted a total of 30 minutes playtime. He’s somewhat upset, thinking he did something wrong.

Interesting feedback - I’m sure Sphero (owners of littleBits) would be aware of this by now. Making things harder is the Droid kit is end of life, so it’s hard to get hold of these days.

With that said, it might be under warranty still. I know we happen to keep spares of some parts for retired gear, though they are naturally reserved for our past customers. Perhaps contact the company you purchased it from to see what the way forward is if it’s within the normal 12-month window.

Robin does make a great point for a DIY repair, though some tinkering would be needed.

The servo in the LittleBits kit can still be found. I was thinking that the Tower Pro SG90 might be a drop in replacement, and cheaper than the Batan B1122.

@Graham any thoughts?

Couple it with this: