Gene Hunter
sage
Reged: 12/29/07
Posts: 292
Loc: SC
|
|
As I have said before I dont think this mirror cell is original, it,s too simple and someone must have thought of it already. I have not seen one like it before though.
The main advantage is that the cell allows you to collimate the mirror or if you want you can move the mirror forward or backward an inch and a half. The design is simple , something that anyone could make.
the drawback to the design though is that the brackets have to be precise or the mirror cell will have tension on it, and also it has to be custom made for a paticular diameter tube.
The T-nuts are glued in the cell with silicone caulk. The reason is that when you move the cell forward there needs to be a slight ability to flex as you are moving the cell out of alignment with the bolts. So the holes for the t-nut are slightly over drilled and silicone in place to allow flex if needed. I think I will find another way to just use rubber washers here and somehow lock the t-nut in place. But this is just a prototype to see how it works.
Sometimes you dont see the flaws in a paticular design till it's made. I still need to test it under regular conditions and see how well it works moving the mirror forward and back.
This design could be modified to work with a regular mirror also.
I would be interested to hear your thoughts on this paticular design and any flaws you think it may have other than what I mentioned.
Edited by Gene Hunter (09/11/08 04:12 PM)
|
Gene Hunter
sage
Reged: 12/29/07
Posts: 292
Loc: SC
|
|
Another advantage to this design is that its only one plate and not two. the CF I used is 1/4 inch thick , extremely light weight and could easily hold two grown men. I think its as strong as 1/2 steel plate. ridiculous.
--------------------
Clear Skies
|
gatorengineer
scholastic sledgehammer
Reged: 02/28/05
Posts: 919
Loc: Hellertown, PA
|
|
Beautiful work Gene, How did you cut it so smoothly? I thought it would fray.
Mark
--------------------
20" F5 Dob
16" Dob in pieces
Meade SN 6 F3.6 with MPCC ---
12" Doc Clay Sky Patrol MEADE SCT
12.5" F4 Newt under construction
Siebert 45mm Binoviewers
Lots of binos---
Optics Past - MN-71, Comet Catcher, 8" Stf Mak, 4" B&W triplet, 6"Schmidt newt, 12"LX200, C8, Meade LX10-10", 10" MEADE ACF, SN8, TAL150K, Orion 150MC, Jason 60mm refractor, ATM 6" F8, WO 110FLT, 92mm Off Axis Newt, Televue Genesis, Nikon 20x120 bino's, 15x110 Boarderguards, Kuhne Flaks
|
Houdini
professor emeritus
Reged: 07/13/07
Posts: 579
Loc: Europe
|
|
Gene, a very neat implementation!
I use a similar design (but less elegant implementation) for a regular 16"x1.4" mirror. It's an 18-point mirror cell with roller bearing edge posts, an integrated fan, and collimation from the top of the mirror box.
It works really well.
Robert
--------------------
16" f/4.9 motorized alt-az, 25" f/5 Dobson, 43" f/4 alt-az under construction
Mirror Edge Support Calculator
|
Gene Hunter
sage
Reged: 12/29/07
Posts: 292
Loc: SC
|
|
Mark, jigsaw works fine with a lite sanding afterwards. It does not fray much at all. Its more like a composite than carbon fiber at this point.
Robert, I too thought of using a roller of some type, but this seemed to me more simple and should have less flex.
My primary goal was something rigid but having the ability to move forward for when you need to change out accessories like a focal reducer or HA filter.
I cant tell you how many times , I have went to insert a paticular combination only to find that it wont come to focus.
20 turns per inch means you turn each of the knobs 20 times and you are one inch closer or farther away. I think thats pretty cool myself.
--------------------
Clear Skies
|
Houdini
professor emeritus
Reged: 07/13/07
Posts: 579
Loc: Europe
|
|
I have about 40 mm (1.6 inch) of collimation space, but of course if you move the mirror significantly you alter the balance of the scope.
Robert
--------------------
16" f/4.9 motorized alt-az, 25" f/5 Dobson, 43" f/4 alt-az under construction
Mirror Edge Support Calculator
|
Luigi
Postmaster
Reged: 07/03/07
Posts: 5272
Loc: MA
|
|
Nice, and the carbon plate may be stiff enough, but the force this plate needs to resist is bending. Having the webs vertical (like a diagonal spider) would greatly increase the bending stiffness with a small increase in weight. You'd have to add a central hub to join the vertical plates, but the plates could have holes or cutouts without greatly reducing their in-plane stiffness.
--------------------
17.5" f/5 Dob. IM-715 MCT. 120ED. Lunt 60mm Ha.
Zeiss, Leica, Fujinon, Nikon, Pentax, Bushnell bins
|
Gene Hunter
sage
Reged: 12/29/07
Posts: 292
Loc: SC
|
|
I thought about that and I was prepared to add that, but seriously this thing is super strong, I can not flex it with all my strength. I was going to add support if needed but I just dont see a need.
--------------------
Clear Skies
|
Gene Hunter
sage
Reged: 12/29/07
Posts: 292
Loc: SC
|
|
one of the most difficult decisions when building a new scope is where to put the secondary and focuser, I mean its impossible to calculate for every piece of hardware you might plug in to the focuser. you might have a DSLR camera, focal reducer, HA filter, Filter , new CCD Camera, etc... and its imposible to know what you dont yet have. So the difficult part for me is figuring out how much room to leave.
This mirror cell takes away that issue all together as you now can move your mirror without changing anything or drilling new holes. But you do have to re-collimate.
--------------------
Clear Skies
|
Brian Reed
Vendor (Round Table Platforms)
Reged: 10/29/04
Posts: 389
Loc: North East Illinois
|
|
That's a great design! I use a Mallincam so in-focus is a big issue as you decrease the focal length.
I think a search though McMaster Carr will probably turn up a rubberized bushing or something else that will solve the tension problem.
I book marked this link and certainly will be borrowing the "Gene Hunter Mirror Cell" for my next scope. 
Here is the (not so elegant) solution on my 10-inch
--------------------
Brian
10-F5.6
8-F7
|
Spoonsize
Vendor/Clothing
Reged: 08/27/04
Posts: 3334
|
|
Houdini:
I really like that design....the knobs could even be extended with rods to extend thru to the front of the scope to enable collimation while looking thru the eyepiece and reaching the knobs at the front.
|
Gene Hunter
sage
Reged: 12/29/07
Posts: 292
Loc: SC
|
|
on the back side you can see the t-nut and how it sits against the cell.
there are 12 layers of 6k carbon fiber in this cell. every other one is turned 45 degrees so that the fibers run every direction for maximun rigidity. the cell is not clear coated as its not something you would see anyway.
this prototype has galvanized steel brackets and stainless hardware but you could use aluminum for the brackets.
If anyone is interested in Carbon Fiber panel to cut out your own mirror cell of any design shoot me an email and we can discuss the costs. Its fairly easy to make CF panels and there is not a lot of labor costs. You cut it yourself and I just make the panels.
--------------------
Clear Skies
|
Spoonsize
Vendor/Clothing
Reged: 08/27/04
Posts: 3334
|
|
I see this one could also have the knobs placed at the front of the tube to facilitate use.
|
Gene Hunter
sage
Reged: 12/29/07
Posts: 292
Loc: SC
|
|
If you mean the ability to collimate from the eyepiece end, i suppose you could but that length of bolt would be heavy.
--------------------
Clear Skies
|
Spoonsize
Vendor/Clothing
Reged: 08/27/04
Posts: 3334
|
|
Perhaps, but couldn't it also be made of plastic/fiberglass/kevlar?
|
Gene Hunter
sage
Reged: 12/29/07
Posts: 292
Loc: SC
|
|
that it could , I am sure, I have not found a source for that yet though. But an excellent idea.
--------------------
Clear Skies
|
jpcannavo
sage
Reged: 02/21/05
Posts: 353
Loc: Long Island New York
|
|
The front collimation technique is very achievable and effective. It was used on my previous Royce16, and will soon be implemnted on my Zambuto 16. Personally, I'll never go back to the old - behind the mirror - method.
Joe
Collimation Rods
Mirror Cell
--------------------
Joseph Cannavo
16" F5 Zambuto w/front collimating mirror cell
Dob Driver with novel azimuth friction clutch, and axial (rotating) electrical connection
Tom Osypowski equatorial platform
10" F5 Lightbridge
Mid 70's RV-6
4" Orion 100mm ED
Mr Keeyoots (My Cat)
|
Gene Hunter
sage
Reged: 12/29/07
Posts: 292
Loc: SC
|
|
Would love to see photo of how you implemented it if you have some.
--------------------
Clear Skies
|
jpcannavo
sage
Reged: 02/21/05
Posts: 353
Loc: Long Island New York
|
|
Gene
Bravo on your design!
I have various photos, I will post these within a couple of days under a thread decribing my EP accessible front collimating mirror box/flotation cell for my F5 16" (Also, be sure to scroll up/down in the links I gave above to see previous photos). Basically the idea is to get the collimation mechanism out to the corners/edges of the mirror box - as also seen in Robs approach above. (An added benifit here is also that it allows a lower profile - i.e. mirror closer to bottom of box) It is then a simple matter to extend "collimation rods" up towards the EP. I used aluminum rods - roughly 1/2" OD. I was surprised how stiff these are wrt torsion (twisting) even with the long length. The result is a very solid feel when collimating at the EP. As Far as I am concerned EP accessible collomation is the way to go!
This topic came up at the Oregon Star Party, a few weeks ago, where I had a chance to observe with Steve Swayze, and a scope with one of his mirrors (great mirror!). One of the group noted how when collimation is a tad off, the "sweet spot" of the mirror moves away from the field center, and how it is a hassle to disengage from the target and tweak things. But with an EP accessible mechanism, this becomes almost as straight forward a focusing!
I'll get some photos up soon
Joe
Edited by jpcannavo (09/14/08 02:13 PM)
|
Spoonsize
Vendor/Clothing
Reged: 08/27/04
Posts: 3334
|
|
Quote:
that it could , I am sure, I have not found a source for that yet though. But an excellent idea.
There are some rods available in the kite making parts section of
www.intothewind.com
ie: 3/16" X 48" fiberglass rods for $1.90 each....
|
Previous
Index
Next
Threaded
Edit
Reply
Quote
[Re: 