500mm on a motorized barn door tracker?

Update; recieved the Celestron Logic Drive and .... what a disapointment! Wayyyyyyy to slow rpm's on this drive. It's like 5-6 minutes/1 rpm. Trying to mod it and if that fails I'm gonna look for a stepper motor and add a speedcontrol.

Wow that looks amazing. Keep us updated with the progress. I'm very interested in the finished product!

KingRiver wrote in post #15606482
Update; recieved the Celestron Logic Drive and .... what a disapointment! Wayyyyyyy to slow rpm's on this drive. It's like 5-6 minutes/1 rpm. Trying to mod it and if that fails I'm gonna look for a stepper motor and add a speedcontrol.

that slow even turned up all the way? I would call celestron on that or send it back. I have one that came from a cheap zhummell and it works the way it should

calypsob wrote in post #15615456
that slow even turned up all the way? I would call celestron on that or send it back. I have one that came from a cheap zhummell and it works the way it should

Yes, its that slow even turned up to max. As I read in another forum - "Upon receipt, examination of the motor drive revealed that it is of the continuously-variable type, capable of speeds from 1/20 rpm to 1/6 rpm inclusive, with the ability to reverse rotation. It is supplied with two brackets, as well as a somewhat flexible coupling for the drive shaft. Power is supplied by a single 9-volt battery "
That's my experience also. Tried to raise the voltage in steps of 0.5V to 12 volts directly to motor with no success....same speeds. You simply would have to dismantle the gearbox and exchange the gears inside. Thats if you find anything that suits. I'd rather sell it and look for a stepper motor with speed control unit. Looking for a simple,suitable control unit atm. There are some small,6V driven and 1rpm/min motors on Ebay but then you are stuck at that rpm with no chance to set rpm according to focallength.

The Celestron one is working the way it should. It's intended for a mount with a 1:144 worm gear for the final drive. A day is 1440 minutes long so the motor output should turn at 1 rev every 10 minutes.
Even if you get a stepper motor drive, it will still need gearing so you're bypassing the real issue which is knowing what speed you actually want. You need to work that out using the distance from the hinge to your threaded rod and how many threads per inch/cm your rod is. The rate is the same, regardless of the lens you put on it ie. 1 rev per day at the camera. Once you know what rate you need at the rod, then you can go shopping for a gearhead motor that suits.

If the math isn't your thing, post up the numbers and someone here will work it out for you.

SteveInNZ wrote in post #15620094
The Celestron one is working the way it should. It's intended for a mount with a 1:144 worm gear for the final drive. A day is 1440 minutes long so the motor output should turn at 1 rev every 10 minutes.
Even if you get a stepper motor drive, it will still need gearing so you're bypassing the real issue which is knowing what speed you actually want. You need to work that out using the distance from the hinge to your threaded rod and how many threads per inch/cm your rod is. The rate is the same, regardless of the lens you put on it ie. 1 rev per day at the camera. Once you know what rate you need at the rod, then you can go shopping for a gearhead motor that suits.

If the math isn't your thing, post up the numbers and someone here will work it out for you.

-Never said it was broken or not working as it should. It just don't fit my needs.

SteveInNZ wrote in post #15620094
If the math isn't your thing, post up the numbers and someone here will work it out for you.

I'm also in the middle of building a barn door mount out of wood with a synchro .8 rpm motor and spent the last few hours scouring the net for information about them.

I turned up this handy formula for working out the maths behind it all.

R=RPM/(0.004375*tpi) where 'R' is distance between the centre of the hinge and the hole for the drive screw and 'tpi' is threads per inch on the lead screw.

neimad19 wrote in post #15621835
I turned up this handy formula for working out the maths behind it all.

R=RPM/(0.004375*tpi) where 'R' is distance between the centre of the hinge and the hole for the drive screw and 'tpi' is threads per inch on the lead screw.

Chcecking this against Gary Seronik's site he has a 4 RPM motor, 32 TPI drive bolt and 7.14 from the hinge to the drive bolt

7.14=4/(.004375*32)
7.14=4/(.14)
7.14=28.572

Not sure if I have missed something here.

the jimmy wrote in post #15622701
Chcecking this against Gary Seronik's site he has a 4 RPM motor, 32 TPI drive bolt and 7.14 from the hinge to the drive bolt

7.14=4/(.004375*32)
7.14=4/(.14)
7.14=28.572

Not sure if I have missed something here.

Under the paragraph "The Drive and Electronics" he explains that he uses a set of gears to reduce the 4 RPM down to 1 RPM at the drive bolt

Radius = 1(which is the rpm at the drive screw after the gears)/(.004375*32)
R = 7.14

I probably should have mentioned that "RPM" is measured at the drive screw after the gearing. Not straight from the motor. Unless your direct driving your mount with a really slow motor without gears

neimad19 wrote in post #15624128
Under the paragraph "The Drive and Electronics" he explains that he uses a set of gears to reduce the 4 RPM down to 1 RPM at the drive bolt

Radius = 1(which is the rpm at the drive screw after the gears)/(.004375*32)
R = 7.14

Good catch, I went over this several times, B4 coffee

KingRiver wrote in post #15619339
Yes, its that slow even turned up to max. As I read in another forum - "Upon receipt, examination of the motor drive revealed that it is of the continuously-variable type, capable of speeds from 1/20 rpm to 1/6 rpm inclusive, with the ability to reverse rotation. It is supplied with two brackets, as well as a somewhat flexible coupling for the drive shaft. Power is supplied by a single 9-volt battery "
That's my experience also. Tried to raise the voltage in steps of 0.5V to 12 volts directly to motor with no success....same speeds. You simply would have to dismantle the gearbox and exchange the gears inside. Thats if you find anything that suits. I'd rather sell it and look for a stepper motor with speed control unit. Looking for a simple,suitable control unit atm. There are some small,6V driven and 1rpm/min motors on Ebay but then you are stuck at that rpm with no chance to set rpm according to focallength.

I'm sorry to hear that the motor is not living up to what you had hoped it would be. This site is really good for finding low rpm motor parts and gears. You may even be able to find an appropriate worm gear which in turn could be paired with the appropriate main gear to rotate the barndoor thread at the right speed http://www.servocity.c​om/ . After reading Steve's comment I realized what he was talking about. Looking at my old cheap EQ mount, the motor drive is connected to a worm gear and the gear for the DEC axis is fitted on top of the worm gear so I am guessing the teeth on the DEC axis are numbered appropriately to match a formula with the worm gear and output speed of the drive motor.

I was browsing servo city again and came across this, may be of interest if you can apply the formula to this design, only $20 more than the celestron drive you purchased http://www.servocity.c​om …haft_worm_drive​_gear.html

calypsob wrote in post #15630548
I was browsing servo city again and came across this, may be of interest if you can apply the formula to this design, only $20 more than the celestron drive you purchased http://www.servocity.c​om …haft_worm_drive​_gear.html

-Thank you. Will have a look....still considering other solutions.

Celestron also makes a motor setup for the EQ4 which is considerably more money than the smaller eq motor http://www.celestron.c​om …e-da-for-cg-4-mounts.html but you would be stuck with an unusable ra motor