TheSkySearchers

Hi all.

Hope everyone is staying safe.

Not sure this is an easy question to answer yet on a barn door trap how many millimetres does the trap open per minute?

Reason I ask is I've been given an electric piston that moves at 48mm a second which I'm hoping to slow down to the required rate yet don't know how many mm it needs to be?

I've tried with the gear system yet cant quite get that right so want to play with a new design.

Any help would be greatly appreciated

Thankyou....

Carl

Carl

The piston will need to rotate your camera at a rate of 15 (360/24) degrees per hour. Which is 0.25 degrees per minute. So the piston will have to be at whatever distance from the barn door hinge is required to achieve this.

You could calculate it approximately then set up a calibration experiment at night.

Regards

Graeme

It is up to you to design the barn door so that your 48mm per second gives you the correct tracking rate.

[edit] OK, I did the math for you. The piston would have to be 550 metres from the hinge, so forget a direct drive! You will need to gear it down. Figure out whatever speed reduction or gearing you can get to work, then design the barn door to fit whatever drive rate you end up with.

I did a quick measurement of mine (it's a curved rod tho) and it seems to be just over 1mm. I have to go to work now, but if you want when I get in I can measure it with a caliper.

All the best,

Thefatkitty wrote: ↑Sat May 09, 2020 2:30 pm I did a quick measurement of mine (it's a curved rod tho) and it seems to be just over 1mm. I have to go to work now, but if you want when I get in I can measure it with a caliper.

All the best,

I have the curved rod on my trap yet will have to abandon that idea as will be attaching the piston end to the upper wooden part that holds the camera.

1mm sounds about right (if I imagine it in my head) so no need for calipers....yet!

Its 5.38pm UK time and I'm about to see if I can get it slowed down enough with enough power to push....

If it fails....I'll stick it on ebay.....a quick Google search showed the piston is worth £96.50!!

Cheers mate

Well, I managed to slow the piston to about 8mm a minute which is too fast so have to scrub that idea.

Still, I'm loving the experimenting!