Focus motor bracket for TEC-140...

[perfrej]

So, Yuri makes his own focuser these days and the Feathertouch is no longer his choice. The TEC Large Focuser is very good; in fact even better than the FT. It uses a pure fit principle, like an old glass syringe where the piston just fits. No bearings, no adjustments and he guarantees that a fully extended draw tube will sag less than 20um when exposed to 3.5 kg of load!

Thing is, the early examples have no holes for motor bracket mounting but the newer ones do. I have the former... Using a Baader belt drive motor you have to hook up to the 10:1 knob, which unfortunately is not hard-connected to the gearing, so it slips a little. That is fine for finger use but a total catastrophe for motor use.

I like my Lakeside motors. I use them in bipolar mode (you have to separate two wires in the connector) from my own hardware driver and they simply perform. They can also be stepped at 330 Hz and have an integral reduction gear making them both fast and accurate.

Needless to say, I need to attach a Lakeside but I do not have any mounting holes. To the rescue comes Designspark Mechanical, my dusty 3D printer, 4741.4 mm of white PLA and four M4 grub-screws

So this attaches to the primary axis housing with a tight fit and four grub-screws. The only force to contain is the rotation - the motor is firmly in place with the axis-coupling.

Going down to Olly's on the 9th to put it on the TEC. I'll report how it goes!

All the best,

DIY Per

[ollypenrice]

That's very impressive. Incredibly convenient to be able to create custom parts like that.

Now then, as for the new TEC versus the old Feathertouch, 'A slipping friction drive is better than an infallible geared one. Discuss'       

Olly (Does he by any chance have the old Feathertouch on his TEC? Might have, might have....  )

[perfrej]

OK, let's get things straight here... The new TEC focuser is a rack and pinion that has a friction coupled 10:1 knob. That's all. It is not a good solution - for the 10:1 knob. In all other "drive" respects it is equal to the FT. The cool thing about it is the absence of bearings and draw tube adjustments. There are none of either kind - just a tight fit with no sag whatsoever. This is the same principle as the Baader Hyperion focuser, the old school Carl Zeiss ones, and now the TEC one adds itself to the bunch.

I notice that I posted this in the wrong section. Any moderator that cares to move it to the "normal" DIY section? Please go ahead...

/p

[ollypenrice]

OK, let's get things straight here... The new TEC focuser is a rack and pinion that has a friction coupled 10:1 knob. That's all. It is not a good solution - for the 10:1 knob. In all other "drive" respects it is equal to the FT. The cool thing about it is the absence of bearings and draw tube adjustments. There are none of either kind - just a tight fit with no sag whatsoever. This is the same principle as the Baader Hyperion focuser, the old school Carl Zeiss ones, and now the TEC one adds itself to the bunch.

I notice that I posted this in the wrong section. Any moderator that cares to move it to the "normal" DIY section? Please go ahead...

/p

Yes, more seriously I think the fricition drive on the slow-mo might well be a good idea. Anyway, my list of things to be 3D printed is already on its seventh page so I'd better not fall out with you!

lly

[perfrej]

OK, send me the list.... We can do some designing when I'm down - it is very quick!

/p

[NickK]

I can see you two sitting heatedly discussing astro over a wine and bread lunch, sat out side in a monet-esque cafe in france.. :smirk:

Anyone actually tried a direct drive focuser? Ie the magnets in the focusing tube are held in place with field flux?

[perfrej]

Me has - almost! My hardware design allows 8x micro-stepping and total lock with field flux. It is the only way you can force the motor to be stationary in between physical steps. I draws about 200mA and generates some heat on the driver's H-bridge but works just fine! It does the high precision stuff but doesn't involve making a motor winding out of the draw tube. Should be doable, though... 0.2 ms from outmost to inmost and with 400,000 steps in between. Whoa!

/per

[perfrej]

And here's "The Movie"...

http://filer.frejvall.se/Lakeside.mp4

/p

[Gina]

By Jove Per you've got your Velleman running fast

[Horwig]

And here's "The Movie"...

http://filer.frejvall.se/Lakeside.mp4

/p

Dear father Christmas, please disregard my previous list, I want one of these!     

[perfrej]

Installed with a snug fit and works perfectly! I'll shot a photo later today