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Equipment Discussions >> Reflectors

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nevy
professor emeritus
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Reged: 02/07/12

Loc: UK
Re: Thermal Issues and Fans Successes new [Re: Mark Peterman]
      #5794887 - 04/12/13 04:50 PM

Here's mine
[image]http://[/image]

[image]http://[/image]

[image]http://[/image]


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azure1961p
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Reged: 01/17/09

Loc: USA
Re: Thermal Issues and Fans Successes new [Re: nevy]
      #5795762 - 04/13/13 01:48 AM

Beautifully executed. I must confess for as much as Im ecstatic with my fan setup it is a little rough around the edges in terms of finish. You by contrast have a terrific machined look about your fan work. Bravo!

Pete


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buddyjesus
Carpal Tunnel
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Reged: 07/07/10

Loc: Davison, Michigan
Re: Thermal Issues and Fans Successes new [Re: azure1961p]
      #5795800 - 04/13/13 03:21 AM

this thread has been wonderful for giving me ideas for tuning my future dob. I just wanted to thank you all.

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azure1961p
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Reged: 01/17/09

Loc: USA
Re: Thermal Issues and Fans Successes new [Re: buddyjesus]
      #5797971 - 04/14/13 08:54 AM

And Buddy, its so cheap to do.

Pete


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nevy
professor emeritus
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Reged: 02/07/12

Loc: UK
Re: Thermal Issues and Fans Successes new [Re: azure1961p]
      #5801449 - 04/15/13 08:29 PM

Quote:

Beautifully executed. I must confess for as much as Im ecstatic with my fan setup it is a little rough around the edges in terms of finish. You by contrast have a terrific machined look about your fan work. Bravo!

Pete




Thanks pete , the machined look is what I was after , I did do a mock up with Perspex but I didn't like the way it looked and it leaked like a sift ,
[image]http://[/image]

I'm very pleased with how it turned out so I'm about to do a similar thing to my 16" lightbridge , I'll post some pictures when it's done.


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UniversalMaster
professor emeritus


Reged: 11/20/08

Re: Thermal Issues and Fans Successes new [Re: nevy]
      #5801838 - 04/16/13 12:41 AM

Hi nevy!

Is the fan sucking or blowing?
Very nice looking setup by the way :-)

Best regards
Søren


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nevy
professor emeritus
*****

Reged: 02/07/12

Loc: UK
Re: Thermal Issues and Fans Successes new [Re: UniversalMaster]
      #5802032 - 04/16/13 06:17 AM

Hello soren , thanks, it blows on the back of the mirror and sends a nice flow of air up the tube, I noticed on my lightbridge that the planetary images got alot sharper with the fan running and I noticed that you can start viewing alot sooner before the scope is fully cooled , I think that's mainly down to the tube currents are being pushed out of the tube instead of lingering in the light path , although with my lightbridge there isn't a baffle so I think alot of the pushed air was being wasted by bouncing back off the back of the mirror , so I decided to make an airtight baffle on my 12" scope to make the fan alot more efficient , now with the baffle on the airflow is alot stronger.
I made it from 2mm mild steel so that it would add weight to the bottom of the scope because I was having trouble balancing when using heavy eyepiece combinations and I was faffing about adding & sliding counterweights al the time , it weighs just over a kilo and it now balances alot better now.


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nevy
professor emeritus
*****

Reged: 02/07/12

Loc: UK
Re: Thermal Issues and Fans Successes new [Re: nevy]
      #5802059 - 04/16/13 07:07 AM

Here are a few photos I took along the way,
This is just after I cut it out and drilled the holes
[image]http://[/image]

After a bit of a clean up
[image]http://[/image]

This is how I was able to paint both sides without having to wait for each side to dry
[image]http://[/image]

[image]http://[/image]

I used this stuff to create a seal because there was a 2 mm gap all the way round the cell around the collimation sticky out bits , this stuff is 3mm thick , it can then be compressed about 1 mm to form a seal ,
[image]http://[/image]
the cell is made from cast aluminium so it's not that flat or uniform

[image]http://[/image]

[image]http://[/image]

[image]http://[/image]

This is before the fan is switched on
[image]http://[/image]

And this is with the fan running
[image]http://[/image]

The fan is totally vibration free and quiet , so I can probly leave it on full speed but if I want to slow it down I can do it by lowering the voltage with this
[image]http://[/image]
Or these
[image]http://[/image]

[image]http://[/image]

I'm used to working with wood so I found metal a bit of a challenge but I just treated it as a very hard wood ;-)
I'm in the process of making a baffle for the 16" lightbridge now so I'll take a few photos on the way to show some of the tools & techniques I used.


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Project Galileo
scholastic sledgehammer
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Reged: 11/14/07

Loc: Jefferson County, Colorado
Re: Thermal Issues and Fans Successes new [Re: nevy]
      #5804264 - 04/17/13 10:23 AM

That looks excellent! I am a fan of the sealed, steel, counter weight baffle. I love the simplicity and how yours looks like it came from the manufacturer that way. Cudos on your modification!

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nevy
professor emeritus
*****

Reged: 02/07/12

Loc: UK
Re: Thermal Issues and Fans Successes new [Re: Project Galileo]
      #5809155 - 04/19/13 05:42 PM

Quote:

That looks excellent! I am a fan of the sealed, steel, counter weight baffle. I love the simplicity and how yours looks like it came from the manufacturer that way. Cudos on your modification!



Thanks mate , I've seen the thread you did on your lightbridge , that's where I got the idea from for the noise blocker fan , I took my stock fan out of my lightbridge today ( I thought it was very smooth & I never noticed any vibrations from it ) while it was out I had it running and was holding it between my fingers and I could feel it vibrating I then did it with the noise blocker and I felt nothing , noise blocker fans are awsome.
I don't think it would have been possible to mount a standard fan to the baffle that's attached to the cell without some vibrations , with the noise blocker it's not an issue.

Edited by nevy (04/19/13 05:45 PM)


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nevy
professor emeritus
*****

Reged: 02/07/12

Loc: UK
Re: Thermal Issues and Fans Successes new [Re: nevy]
      #5824946 - 04/26/13 05:30 PM

I just finished making the baffle for the 16" lightbridge , I've not had a chance to put the scope back together yet , so here's a quick preview.
[image]http://[/image]

[image]http://[/image]


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rockethead26
Carpal Tunnel
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Reged: 10/21/09

Loc: Arizona, USA
Re: Thermal Issues and Fans Successes new [Re: nevy]
      #5825346 - 04/26/13 09:28 PM

Really nicely done, Nevy!

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nevy
professor emeritus
*****

Reged: 02/07/12

Loc: UK
Re: Thermal Issues and Fans Successes new [Re: rockethead26]
      #5826406 - 04/27/13 02:03 PM

Thanks jim.

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nevy
professor emeritus
*****

Reged: 02/07/12

Loc: UK
Re: Thermal Issues and Fans Successes new [Re: nevy]
      #5833276 - 04/30/13 09:44 PM

I didn't like the look of the bolt heads on the feet so I changed them for some bigger stainless ones
[image]http://[/image]
I took a few photos on the way to show how it was done ,
I started by cutting the circle out being carefull to cut just outside the line
[image]http://[/image]

[image]http://[/image]

I then used a belt sander clamped to a workbench to sand it down to the line using 60 grit aluminium oxide ( it's neater that way and gives a nice smooth finnish)
[image]http://[/image]

[image]http://[/image]

That went well , I got a nice fit with a couple of millimetres gap all round
[image]http://[/image]

Next I needed to drill some holes so the baffle could clear the sticky out bits in the cell , to do this I used a portable drill press and a hole cutter
[image]http://[/image]

[image]http://[/image]

[image]http://[/image]

Next I needed to cut the middle circle out for the fan and then mark the baffle where the fan will be so as to have it nice and squared up

[image]http://[/image]

All done , now for a bit of sanding to get it ready for paint
[image]http://[/image]

[image]http://[/image]

It all went well but I wasn't happy with only a few millimetres clearance between the fan and the floor when the LTA was standing on the floor , I looked online for some slightly longer feet but could only find the same size or way to big & bulky , so I decided to make my own from a couple of circles cut from Baltic birch plywood glued together and cut to the right length.
I wanted them to look like the original plastic ones so I thought I would shape them. I don't own a lathe so I rigged up a drill press with an adjustable table and used a belt from my belt sander wrapped round a piece of wood to shape the feet to a taper
[image]http://[/image]
It worked , they turned out nice after a couple of coats of paint,
[image]http://[/image]
I decided to make the 7 mm longer than the originals and with the bolt heads left flush on the bottom that would give me another 5 mm ( the bolt head would stop the paint getting chipped off aswell )

I used this stuff, 3 mm sticky back high density foam ( draught excluder ) to make an airtight seal
[image]http://[/image]

[image]http://[/image]

Now it was time to stick it all together , starting with mounting & wiring the fan to the baffle
[image]http://[/image]
There was One thing I forgot to photograph and that was the 1.6 mm plastic washers I put between the cell and the baffle to only allow the foam to be compressed by 1.4 mm so as not to deform the metal and also so I could tighten all three bolts down by the same amount , by the way the fixing for the baffle is by the three bolts that goes through the feet , that's also another reason I needed different feet as the bolt on the originals weren't quite long enough.

And now its time to put the cell back on
[image]http://[/image]

And now for the mirror , but it needs a bit of a wash first
[image]http://[/image]

All washed & ready to go
[image]http://[/image]

All clamped in and ready , I find the thickness of business cards a bit much for setting the gap between the clips and the mirror so I use writing paper , setting it so it slides under the clips easily and being able to just feel a little resistance as it easily slides out
[image]http://[/image]

All back together and ready to go
[image]http://[/image]

Here's a comparison of the heightof the old feet & the new ones
[image]http://[/image]

Now there's plenty of clearence
[image]http://[/image]

It's been a bit of a chore having to wait for good weather so I can get it done ( I have to work out in the garden cause my sheds are to cramped to work in) but its all over now and here's the end result
[image]http://[/image]
.


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azure1961p
Postmaster
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Reged: 01/17/09

Loc: USA
Re: Thermal Issues and Fans Successes new [Re: nevy]
      #5833309 - 04/30/13 10:09 PM

You ARE the craftsman! The great job you did with the jigsaw is testament to that and the fabrication and finish everywhere else is inspiringly good. I'm seriously impressed.

Pete


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nevy
professor emeritus
*****

Reged: 02/07/12

Loc: UK
Re: Thermal Issues and Fans Successes new [Re: azure1961p]
      #5833408 - 04/30/13 10:57 PM

Thanks pete

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Project Galileo
scholastic sledgehammer
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Reged: 11/14/07

Loc: Jefferson County, Colorado
Re: Thermal Issues and Fans Successes new [Re: nevy]
      #5834002 - 05/01/13 10:17 AM

Nevy, how much did the rear baffle for the Lightbridge weigh when you got it done?

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nevy
professor emeritus
*****

Reged: 02/07/12

Loc: UK
Re: Thermal Issues and Fans Successes [Re: Project Galileo]
      #5834135 - 05/01/13 11:27 AM

Quote:

Nevy, how much did the rear baffle for the Lightbridge weigh when you got it done?



I was going to weigh it when I finished but I got carried away and forgot, but I did weigh it just before I cut out the middle hole for the fan and it weighed slightly under 2.5kg , so with the middle cut out and the fan added it would probly still be 2.5kg ish, before I made the baffle I was using six 1 kg dumbbell weights attached where the locking knobs use to be and it ballenced perfect wherever it was pointed ( even just before zenith) and it stayed put and was very smooth to move. I'm now thinking that I will probly use three 1 1/4 kg weights instead , but in a few months time I will be getting a thinner lighter mirror so I may be back to using the original six 1 kg weights , which is good because without the metal baffle I probly would have had to of added more weights.


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nevy
professor emeritus
*****

Reged: 02/07/12

Loc: UK
Re: Thermal Issues and Fans Successes new [Re: nevy]
      #5852677 - 05/10/13 08:18 PM

Just a quick update , I had the 12" out a couple of nights ago ( the fist time since I installed the new fan & baffle).
And all I can say is that I'm chuffed to bits with it.
Normally when the seeing is good I see a white Saturn with a hint of a belt and nice sharp looking rings with a nice Cassini division , the actuall planet is pretty featureless , now with the fan running it looks a bit different.
The seeing wasn't particularly good the sharpest views were at 142x with a TV 10.5 smoothie, I had the fan running for about an hour to cool the mirror while I went inside and waited for Saturn to rise.
The first thing I did was to turn the fan off & the view of saturn was not really that sharp , it was shimmering quite a bit through bad seeing and it would steady now & again and the rings were ok ish Cassini division coming and going , I then switched the fan on and after a few seconds I could see a real difference , the shimmering calmed down quite alot , the planet & rings got alot sharper with the Cassini division there all the time but the main differences was on the planet itself , I could see two bands and I could see a bit of detail in the polar region , I think the reason for this is that for the first time I could see a bit of colour instead of just white and this made the bands more visible , it was like a beige creamy colour on one band and the next band was a slightly darker ( browner ) shade & there was a subtle colour difference coming and going in the lower polar region , I switched to the tv clickstop 8-24 zoom and I was getting just as good views from it even at the 8 mm setting.
So on first impressions its made a huge difference , I can't wait to try again in good seeing , when I first put the fan on the scope it did make for a sharper image but after the sealed baffle system was installed I was surprised to be able to see colour which in turn made bands more obviousness.
So it was well worth doing and I'm looking forward to trying the lightbridge out as that gives even better planetary views with just the standard fan with no baffle so I have high hopes for it now , can't wait.


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