Twist Box servo pops out


I received also my servo and electronic part and I was looking forward to build up my Marty with my printed parts. Unfortunately the normal servo in the Twist Box is shaking around. It is only fixed by one flange (mounting point) and the gear. But the other flange is free and you can move the servo between the gap from the two parts (1a).

The result was that the servo pops out from the horn while I carefully twisted the leg. Does everybody has the same problem or is there a workaround to fix this issue?

Thank you Patrick


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5 Responses

chaoscrack OP

@kjw At the printed version there are washers too and this distance is ok.

@angus Thank you for the linkt to the other instruction. Between this two instructions are a big different. At the printed version you have to place the horn separately and afterwards you have to push the servo into the horn. So there is no fixation with a screw as it is in the other version.

In my case I printed a adappter as you can see in a additional photo at the dropbox folder. Now my servo isn't longer moving.

05:11:28, 28th August 2017   |   Permalink   |   View Source
angus STAFF

In addition to what @kjw said, we normally attached servo horn to the servo with one of the self-tapping screws that come with the servos (looks like a HK15178, same as all the full Marty kits)

The mounts are designed to be able to accommodate a handful of different servos as the exact dimensions aren't standardised, so there's some slop there... If you've self printed @chaoscrack then taking a look at the Injection Moulded instructions might also be useful?

Hope that helps


22:05:40, 27th August 2017  *   |   Permalink   |   View Source

I'm just a fellow builder and I've only built the full kit with injection moulded parts. There are some washers in the full kit for parts around the knee which suggests some fine tuning was required. I suspect that is for friction reduction. Does your knee rotate easily both when it's assembled and when Marty's weight is on it? I'm speculating but perhaps the servo is finding too much resistance and that causes the escape. You've probably already done it but you could have a close inspection of where the servo fits wrt to the 3d model to make sure they printed accurately.

I believe the injection moulded parts are not always identical to the printable ones. You can see the former clearly if you zoom in on the parts list ( The servo horn is contained at one end but not the other until it's mated with the housing. I'm not sure what the terminology is but presumably you are using a servo horn with "two arms" here?

There's a public holiday tomorrow in the UK, it may be Tuesday before you get official help.

21:04:14, 27th August 2017   |   Permalink   |   View Source
chaoscrack OP

Pleas find two pictures at:

15:09:44, 27th August 2017   |   Permalink   |   View Source

A close-up picture might help here?

13:43:33, 27th August 2017   |   Permalink   |   View Source