The Mapstar 22" build

[Uplooker]

Excellent job big man. I had similar convoluted thoughts of such an arrangement myself. Certainly wouldn't have been as finely executed as yours ?

[mapstar]

Spent the afternoon creating lots of brass turnings.

Heres the machining pics 

Two nice shiny blocks ready for the next stage.

Two mounting plates and the T shaped brush holders 

Not quite finished as I've got the hole in the bottom to bore which will accept a 9.5mm spring and 10mm diameter copper brush.

The copper hasn't been delivered as yet so I will finish them hopefully tomorrow.

It is just a case then of drilling two holes through the rocker box bottom and fitting the mounting plates to accept the brush holders.

Another photo of the holders as they will be mounted in the rocker box. Two button head M4 screws retaining each brush box in the mounting plate.

 

Edited March 21, 2017 by mapstar

[Stub Mandrel]

Nice looking mill... what is it?

[Davey-T]

Just what I need, having spent 2 days off and on trying to make a rectangular hole three quarters of the way through a piece of 15mm ally' using a milling bit in a pillar drill 

Dave

[mapstar]

On Tue Mar 21 2017 at 18:44, Stub Mandrel said:

Nice looking mill... what is it?

You may or may not have seen the complete milling machine rebuild here Neil 

http://www.model-engineer.co.uk/forums/postings.asp?th=119748

Edited March 23, 2017 by mapstar

[Stub Mandrel]

Oh dear! I must start paying more attention....

[mapstar]

5 hours ago, Davey-T said:

Just what I need, having spent 2 days off and on trying to make a rectangular hole three quarters of the way through a piece of 15mm ally' using a milling bit in a pillar drill 

Dave

Bring it along to the PSP sure it will get sorted 

[mapstar]

Managed to get the slip rings finished off today  

First off I drilled a 10mm hole in each brush holder to accept the copper rod. Here it is with the brush holder still in the milling machine vice.

The hole had to be deep enough to accept a decent slug of copper for the brush and also the spring. Here we are with all the parts assembled and also the exploded view. I'd soldered a copper braid to each brush for a reliable connection which wouldn't just rely on the spring and copper to brass. The braid was brought through what would be the brush holder top.

A crimped lug then completed the whole assembly. 

Two square section holes were then cut through the lower board of the rocker box using a 1/4" router and a jig.

After these were both cut I gave them a quick coat of paint to seal the ply and inserted the brush holders with a little vaseline to lubricate and stop them tarnishing. 

Pressing one of the brushes down on the spring

It was then a case of refitting the rocker box on the ground board.

The only thing left to do is connect the cable to these with crimped lugs once I know the length to the rocker socket. I will probably fit an insulating cover over these but the power tank is double fused so o.k. for now 

I plugged in the battery and tested at the holders for volts 

Onto the next Mod which is a new Spider 

Damian

 

Edited March 23, 2017 by mapstar

[Demon Barber]

Hi Damian, looking good,your talents show no end, it will really be a great addition to your scope,hope your keeping ok?

Regards

Mike

[Mark62]

Looking good Damian hope you manage to complete it by tomorrow for the starparty 

[mapstar]

2 hours ago, Demon Barber said:

Hi Damian, looking good,your talents show no end, it will really be a great addition to your scope,hope your keeping ok?

Regards

Mike

Cheers Mike as you know I've been meaning to complete this mod for a while.

New spider to document next. Looking at the weather I should be  out tonight but packing for the PSP tomorrow. 

[niallk]

Lovely job!! Great skills

[mapstar]

14 minutes ago, niallk said:

Lovely job!! Great skills

Thanks. More to come 

[Uplooker]

Just a couple of questions:-

1. Did you really need to wear a glove to demonstrate the "push" action of the brush?
2. Another bloody spider? How many will that be?

Regards,

Mr Technical

[mapstar]

3 minutes ago, Uplooker said:

Just a couple of questions:-

1. Did you really need to wear a glove to demonstrate the "push" action of the brush?
2. Another bloody spider? How many will that be?

Regards,

Mr Technical

Answers:-

1 No but it keeps my hands soft 

2 errrrrr MK3 

Hope it's given a few pointers. 

[Chris]

Ok, I can tell I'm going to seriously, seriously, enjoy reading this build thread once I've finished reading your other very impressive thread pertaining to the heart of this Dob, Damian  

Just had a quick skim through so far; all I can say is your Dob is truly priceless and unique, absolutely love the look of it! how cool is a carbon fiber secondary holder! that and the multitude of other thoughtful touches I've only glimpsed at so far. A proper labor of love. 

Plus you have a milling machine which is pretty cool  

[Demon Barber]

Somebody got out the wrong side of the bed!!!!!!!!!!!   

Mike

[mapstar]

59 minutes ago, Chris Lock said:

Ok, I can tell I'm going to seriously, seriously, enjoy reading this build thread once I've finished reading your other very impressive thread pertaining to the heart of this Dob, Damian  

Just had a quick skim through so far; all I can say is your Dob is truly priceless and unique, absolutely love the look of it! how cool is a carbon fiber secondary holder! that and the multitude of other thoughtful touches I've only glimpsed at so far. A proper labor of love. 

Plus you have a milling machine which is pretty cool  

Not quite as epic as the other thread Chris.

Thanks for the recognition, the scope will be hopefully getting some starlight this weekend at the PSP. 

The milling machine rebuild is here if you missed it as it makes for another Interesting read 

http://www.model-engineer.co.uk/forums/postings.asp?th=119748

Edited March 23, 2017 by mapstar

[Physopto]

12 hours ago, mapstar said:

 

1 No but it keeps my hands soft 

 

 

So when is the commercial due out for the hand cream then ?

[gtis]

Hi Damian just read your milling machine rebuild looks great

i also like your mini compressor just the job for painting my 

car bodies 

 

[mapstar]

1 hour ago, gtis said:

Hi Damian just read your milling machine rebuild looks great

i also like your mini compressor just the job for painting my 

car bodies 

 

Very nice Neil 

[mapstar]

The next mod I did was due to rotational  flex of the spider caused by the weight of tge 5 1/4" minor axis secondary. This alters the collimation slightly.

I went through a couple of different versions before settling on whats seen below. The original, then one with an octagonal central boss which had two fixings at the end each Vane. This was stable but I just didn't like the look of it and due to a slight error gave a fifth diffraction spike.  

Having no turning facility I had three aluminium discs laser cut. 2 x 100mm dia x 5mm and one 131mm dia x 6mm thick for the secondary holder top plate.

Next I made the 4 new spider vanes from 1.5mm thick mild steel. The mill playing a huge part in this. I did the drawings for these on CAD software so could've also had them laser cut. Any excuse to make some turnings

I would use the two 100mm dia discs as the top and bottom of the spider central boss joining them with 4 uprights that the vanes would attach to.

Here is the nearly completed spider 

4 tapped collimation holes in the lower disc and some end fixings to allow the four fixing screws at the end of each vane.

After spraying black the spider was installed in the UTA.

Central boss

The secondary dew heater would be connected through the vanes and then via an insulated copper strip across one of the vanes soldered at each end then bonded with epoxy.

All finished it was ready for star testing and I was finally happy with the results.

Clear skies 

Damian

Edited March 28, 2017 by mapstar

[Uplooker]

Hi Damian,

Looking good. Just a quick question as it is not clear to me from the photos. How did you attach the vanes to the central boss? Did you use the screws on the 100mm discs to secure "pillars" between the two and then utilise the 2 off holes in the vanes to fasten to those "pillars"?

Lets hope this the last secondary holder arrangement you need to fashion

[Peter Drew]

I used a similar arrangement to support a 6" minor axis secondary mirror on my 30" build. Seems to work OK so I'm sure yours will. 

[Stub Mandrel]

2 hours ago, Uplooker said:

Lets hope this the last secondary holder arrangement you need to fashion

If he has to do it again it will be a tertiary holder