View Full Version here: : EQ Platform
04-02-2012, 02:41 PM
I have built an EQ Platform that works reasonably well using zinc coated threaded rod for the drive mechanism. It was built as a prototype and so is bigger than it has to be and taller, which makes viewing a bit difficult (with a 12" DOB).
I am building a new platform and was wondering if brass threaded rod would be a better option for the drive. Does anyone know if brass on brass would give a smoother motion than steel on steel?
Thanks in advance
04-02-2012, 03:49 PM
If your threaded rod worked I suggest going for Stainless steel. This would be the stronger and smoothest around. Bras would be smoother but not sure if it's softness would create wear over time.
(Floating ideas) My prototype EQ platform used friction first, then I purchased flexible pinion and ran it of that. The problem with flexible pinion is that it would widen the gear and when the platform reached flat point the drive floated between one direction and the other. While it was on and angle the bond was strong and go very solid running. Friction though was the easiest and best IMO. I didn't use threaded rod because I couldn't bend to give me even rotation.
05-02-2012, 02:59 AM
Being starting one here for a while now lol, i was looking at going a stepper with a 300:1 gear head direct drive, though these are near impossible to find. The next best thing i found was using threaded rod and a tape drive. You could heat treat mild steel with an oxy and dipping into oil then cleaning up with a dye.
05-02-2012, 01:59 PM
I used a stainless steel screw and a plastic sleeve with a plastic tube insert (http://synergous.com/photos/picture.php?/118/category/11). The plastic tube is tapped 6M. Having tried all sorts of combinations of metals etc, this turned out to be the best. Very tight and quiet. Might be asking too much of an ungeared stepper. Tamiya 5:1 planetary - motor speed 5rpm has sufficient torque to drive it though.
05-02-2012, 06:26 PM
Thanks for in input guys.
I think I have a solution, which is stainless steel and brass.
By the way, I looked at stepper motors and was completely confused, and thought about a tape drive, but it seems to take up a fair bit of space.
What I did was use a model aircraft servo, Hi Tec HS311 to be exact, modded for contuinous rotation. I have a bunch of model aircraft stuff laying about so I just used an old transmitter and reciever to control the motor, wireless.
The motor spins at up to 65 rpm so I bodgied up a worm gear box to turn a 8mm threaded rod at about 2rpm.This assembly sits on a piece of ply hinged on the base of the platform so a spring can push the turning rod against another rod fastened to a bit of wood cut to the radius of the southern sector attached to the moving platform.
As Malcom says, there appears to be a problem when the system is perfectly in balance (moving platform horizontal), it floats a bit. I am experimenting with weight bias to keep the system loaded and it seems to work.
Thanks again for responding.
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