a different dob drive system

[BenK]

Hey Mike,

Here are a couple of photos of the Eq platform I made recently..

In the plans a screw thread and tangent arm are suggested to drive the base, but with this set-up there is no slop at all, or tracking errors due to the arm being driven in a straight line.
and to re-position i just release the tension on the cable (like a guitar tensioner) and roll it back to the start position, then tension it again.

The cable goes once round a little roller, driven by a geared down DC motor.

It sure makes viewing more pleasant, with the full sectors it can track for around 90 mins.

I'd like to see what you reckon

Cheers,
Ben

[bojan]

Looks good...
The only potential problem may be a variable rotational speed of the DC motor... but then again, it can be controlled by tracking software or manually.. so it is not a problem :-)

[joshman]

i like it, simple and effective

[rmcpb]

Ben,

Does the cord go around the bearing or is it a straight pull?

Cheers

[BenK]

Hi Rob,

the cord is fixed to one side of the timber sector between the 2 aluminium ones under the dob base, then runs along its circumference, around the pulley/roller (seen on the motor assembly) and to the tensioner on the other side.

so it pulls around its circumference.

the base just rolls on 8 bearings seperate to the drive assembly.

I hope this makes sense...

Cheers

[centauri]

I wonder why people with dob trackers are not using a one way roller clutch in the drive systems, would make it dead easy to push it back to the start again.

[bojan]

I guess because such a clutch would not move the telescope at all ;)

What is needed is a clutch that can be dis-engaged... like the one used here..

OK, maybe it could have been done better, but it is not a problem to reset the whole thing once in an hour...
Maybe a friction clutch, that needs a certain force to start slipping is a better idea....