Geared motors for rubber scale models

[Prosper]

I was tempted to put this in the 'techniques' forum, but since - apart from initial experimentation - I'll be using this for scale models only . . . we-ell, I dunno. But if it's in the wrong forum, then George K, who has the same omnipotence on this site as the Gods on Mt Olympus - will surely move the topic to where it belongs best.

My interest in this subject reawoke because my flying field is off-limits until at least late autumn, and probably until next Spring for models needing some grass cushioning to end their flights.

First of all, an example of what this is all about.

https://youtu.be/L6eHNjIhpbw

This balsa-sheet model has an 11" 280mm wingspan and a 3-blade prop with 3" 76mm disc diameter. Thanks to some gusty flurries of wind yesterday, it was dislodged from high in a tree where I think it was getting broody. No damage except one elevator knocked loose. The wind died completely at evening, and I got a full-turns video'd flight. Unfortunately the ground is very rough and every time I tried to move to acquire the model on camera I I lost my balance. Not so this morning, when the wind was still zero - I was careful to find a level footing amid the tussocks - so a better-recorded flight. Note how high the model is when the turns run out. The motor run equates to an average prop rpm throughout the run of 3440. The motor is two 6" 150mm braided strands of 3/32" rubber. The model has a very high (in my opinion, for a model this size) wingloading. The geared unit is the one in the picture with the 3-blade prop. The gearing is 2.5:1. The prop blade pitch at 75% of disc diameter is 25°.

Over coming days I hope to post about the basic ideas and issues, my earlier experiments, thoughts and findings. Doing this may well repeat things I already said (wrote) on the vanished HPA1 or HPA2.

Stephen.