HEQ5 pro - drive chain

[Guest]

A few questions about the way the drives work on these mounts.

I wondered what is happening internally when you lock and unlock say the RA axis on a mount. I know it's possible to move an axis when it's locked but also it has to be locked in order for the motor to drive the shaft so I assume that there isn't a physical brake being applied but you are just connecting the shaft to the motor drive. Is that right? So when you accidentally move an axis when it should be locked is that likely to do any damage? Or is there a slipping clutch or something?

On the HEQ5 pro there are two stoppers on the side which cover two ends of shafts with flats on one side. I assume that these are left over from the manual operation through a knob or handle. Is that right? If so then is it possible to attach handles to these shafts and operate the mount manually? I realize you wouldn't  normally do that but I can think of some times when it might be useful.

Regarding the encoders. I assume that the encoders are attached on the drive side not on the shaft side so that when a shaft is unlocked and you rotate the shaft manually the encoder doesn't move which is why you shouldn't move the mount manually after alignment. Is that right?

 

[Starflyer]

Take a look at a strip down guide, it'll help you to understand the internals and how the mount and clutches work.

http://www.astro-baby.com/heq5-rebuild/heq5-m1.htm

Occasionally accidentally moving the axis with the clutche locked won't do any damage, it's a brass button pressing against a smooth part of the worm wheel. But I imagine constant moving with the clutch locked would generate brass swarf and that isn't a good thing.

The worm gear shaft is permanently engaged with the stepper motor and you can't operate it with manual slow-mo knobs.

AFAIK there's no encoders on the HEQ5, the mount keeps track of it's position by counting steps of the stepper motor.

 

Hope this helps,

Ian

[JamesF]

To the best of my knowledge, the clutch is just a friction clutch using a small brass bearing that the threaded clutch spindle pushes against.  Releasing the threaded spindle allows the bearing to slide over the surface of a flange on the gear that mates with the worm, allowing the axis to spin freely.  Moving an axis with the clutch locked is therefore possible (if you can overcome the friction), but probably not desirable.

The only thing I can think of that might be the "stoppers" you mention are the covers for the worm bearings (and the holes through which the worms themselves are inserted).  I can't imagine that you could operate the worms manually through these even if it were possible to fit handles as you'd not only be turning the worm gearing, but also trying to turn the stepper motors that drive the worms.  There are a number of step-down gears between the motors and the worms, so they'd probably have a fair bit of mechanical advantage.

Not sure what you mean about encoders though.  Do you mean the setting circles on each axis?

James

[Guest]

Thanks,

Some of the skywatcher mounts have dual encoders and there's a function on the hand set to synchronize encoders so I assumed that on the other mounts there must be just a single encoder. However you are right, there are no encoders on the HEQ5 and it simply counts stepper motor pulses to work out the position, as you said. On another website they called this a virtual encoder but in my book it's not really encoder at all. Anyway, it explains why you have to drive the axis through the motors in order to keep track of positions.

I've found to my cost that is is possible to nudge the axes when struggling to rotate the tube on my Newtonian scope when the drives are engaged.

 

[alacant]

11 hours ago, woodblock said:

is it possible to attach handles to these shafts

Hi. Yes, but not I fear to do what you intend. 

With the motor disengaged, use a piece of rubber tube fitted over the shaft flat ends you mention during adjustment of the gear mesh. Turning the shaft by means of the rubber extension turns the worm, so allowing a check for binding between the worm and the gear. You can slacken off when you find a position where it binds. Do this around 360º and you have as good an adjustment as is possible.

HTH