Mechanical prop brake.

[Michael Barclay]

I am  bulding a Hawker Tempest in fiberglass covered depron, and thinking about landings without u/c.   As I dont know of an electronic  prop. brake which will stop engine rotation at a fixed point, keeping the prop. clear of the ground, I wonder if anyone has developed a mechanical brake which will do this?   On the face of it a rod moving fore and aft in a fixed tube operated by a small servo and engaging a stop on the rear of the spinner could solve the problem. Has anyome experience of trying something like this?

[Gary Manuel]

Such a thing does exist Michael. There is an (expensive commercial) drone that takes off vertically using quad-copter type motors then flies horizontally using wings/forward facing prop. When flying in fixed wing mode, the quad props all stop in alignment with the direction of travel to reduce drag.

I can't remember the name of the drone but I'm sure that someone on here will.

The other alternative is a folding prop.

The other consideration is that I have quite a few belly landers and it's rare that the props get broken as long as power is cut before touchdown.

[J D 8]

I fly a number of belly landers and very rarely does a prop break. The old KK nylon props may not have been the most efficient but they never broke.

[Michael Barclay]

1 hour ago, Gary Manuel said:

Such a thing does exist Michael. There is an (expensive commercial) drone that takes off vertically using quad-copter type motors then flies horizontally using wings/forward facing prop. When flying in fixed wing mode, the quad props all stop in alignment with the direction of travel to reduce drag.

I can't remember the name of the drone but I'm sure that someone on here will.

The other alternative is a folding prop.

The other consideration is that I have quite a few belly landers and it's rare that the props get broken as long as power is cut before touchdown.

Thanks Garry. That's interesting. I doubt a folding prop will work well owing to the large chin on the Tempest. I will try and find details of the drone you speak of.

[john stones 1 - Moderator]

Same as others have said, had plenty belly landers, very rare props broke.

[Michael Barclay]

1 hour ago, J D 8 said:

I fly a number of belly landers and very rarely does a prop break. The old KK nylon props may not have been the most efficient but they never broke.

Great looking model JD. I wasn't so bothered about breaking the odd prop as bending the motor shaft.

[Matt Carlton]

I think the lack of rotational resistance Vs an IC motor would make it unlikely to bend a shaft in a normal landing as the prop would be likely to be pushed horizontal first. On an IC engine that's much harder to do so the routine is to set the prop horizontal at TDC. 

[J D 8]

   With IC you set the prop to stop horizontal when piston is on compression, electric tend to be still turning at touch down but settle horizontal as model skids along. I have never bent a shaft just landing.? Using one to dig a hole in the ground is another matter.?

[Michael Barclay]

Thanks for your replies everyone. Clears things up for me as I have never built a plane without u/c before.