31 replies to this topic

[mrflib]

Can anyone recommend a good machinist in the UK, EU or frankly anywhere? Closer to home obviously preferable. I'm looking to have a machinist thin down the spider vanes of my Vixen vc200l like the attached image. Cheers!

Edited by mrflib, 02 October 2024 - 03:30 AM.

[mrflib]

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[PETER DREW]

As a machinist myself I think this would be a risky business.  I believe the spiders on these telescopes are castings and if so might not have the structural integrity necessary if thinned.  A better approach would be to replace the vanes with a thinner but brass or steel material. I doubt that you would see much difference though as the large secondary accounts for most of the obstruction effect.

[sellsea]

I suspect difficulty in machining an already thin wall because of deflection caused by the force of the cutting tool.

[Notdarkenough]

Fabrication what you want. I just moved from Germany, lived an hour from TS near Saarbrucken. I'd ask those guys if they can fab something, or know someone who can. They are pretty plugged in.

[LDW47]

Can anyone recommend a good machinist in the UK, EU or frankly anywhere? Closer to home obviously preferable. I'm looking to have a machinist thin down the spider vanes of my Vixen vc200l like the attached image. Cheers!

Good luck, unless its a personal friend you likely won't find one, you probably won't want to pay their shop rate, there is no money for them to make on those trivial jobs. Get a couple of different grades of emory cloth and do it yourself, takes time. In the end, all said and done, you will be lucky if you notice a difference.

Edited by LDW47, 02 October 2024 - 02:49 PM.

[The Cloud Gazer]

This seems like a job a 3d printer could do for cheap + you get to keep the original?

Edited by The Cloud Gazer, 02 October 2024 - 03:17 PM.

[PIEJr]

Yet another reason why I'm a Refractor nut.....

 

Reinventing the wheel rarely goes well.

[mrflib]

As a machinist myself I think this would be a risky business. I believe the spiders on these telescopes are castings and if so might not have the structural integrity necessary if thinned. A better approach would be to replace the vanes with a thinner but brass or steel material. I doubt that you would see much difference though as the large secondary accounts for most of the obstruction effect.

Thanks Peter. I know it has been done multiple times but as with investment, past performance doesn't guarantee future gains.

It's not really about the obstruction. It's the fact the veins are very thick and produce square stars.

I'd be willing to take the risk if I could find a good machinist to attempt it. I got the scope extremely cheap.

Take a look at this video https://youtu.be/a75...-2-RGPaG87Tl7ZM

Edited by mrflib, 03 October 2024 - 03:43 AM.

[mrflib]

This seems like a job a 3d printer could do for cheap + you get to keep the original?

Do you think it would be stiff enough?

[Jon Isaacs]

As a machinist myself I think this would be a risky business.  I believe the spiders on these telescopes are castings and if so might not have the structural integrity necessary if thinned.  A better approach would be to replace the vanes with a thinner but brass or steel material. I doubt that you would see much difference though as the large secondary accounts for most of the obstruction effect.

 

I am with Peter on this.  I'm a retired mechanical engineer who worked closely with a number of excellent machinists.. One of the keys to my success as an engineer was always listening to the machinist, I would discuss the designs with them prior to making the actual drawings and then once the drawing was done, I would discuss it with them again.

 

As a mechanical engineer, I see two problems..  The vanes are cast which makes them brittle, they could easily fracture under the vibration and side loading from the mill.  Second, they are not under tension.  What makes thin vanes possible is the fact that they are tensioned.  

 

If you are going to try to thin the vanes, I agree with "notdarkenough", replace the case vanes with tensioned steel vanes.  This could be done by hand with a minimum of tools.  I could even do it. 

 

I would not recommend 3-D printing for a number of reasons.

 

Jon

[The Cloud Gazer]

Do you think it would be stiff enough?

I was thinking carbon fiber, otherwise it is true that regular printed plastic would be a nightmare have good stiffness / reliability and you really don't want it to break... Listen to the others 

(my very first scope 14 years ago was a way too bulky to handle for me reflector that saw barely any use and then went to refractors so my experience in this domain is pretty much inexistent) 

[Tubuskahusk]

How about the guys at Astro Systems. They ship internationally. They have a wide selection and even do custom work. It says customer satisfaction guaranteed. 

 

https://www.astrosys...biz/spiders.htm

[Jon Isaacs]

How about the guys at Astro Systems. They ship internationally. They have a wide selection and even do custom work. It says customer satisfaction guaranteed. 

 

https://www.astrosys...biz/spiders.htm

 

Astro-Systems secondary spiders and secondary holders are used in many Newtonians. The issue with the design is that the secondary holder is mounted using a central bolt which makes the quite tall. 

 

If the stock design attaches the spider to part of the secondary holder as the drawing suggests, there's not enough room, the secondary is too close to the primary.

 

Jon

[mrflib]

I am with Peter on this.  I'm a retired mechanical engineer who worked closely with a number of excellent machinists.. One of the keys to my success as an engineer was always listening to the machinist, I would discuss the designs with them prior to making the actual drawings and then once the drawing was done, I would discuss it with them again.

 

As a mechanical engineer, I see two problems..  The vanes are cast which makes them brittle, they could easily fracture under the vibration and side loading from the mill.  Second, they are not under tension.  What makes thin vanes possible is the fact that they are tensioned.  

 

If you are going to try to thin the vanes, I agree with "notdarkenough", replace the case vanes with tensioned steel vanes.  This could be done by hand with a minimum of tools.  I could even do it. 

 

I would not recommend 3-D printing for a number of reasons.

 

Jon

I won't argue with cold logic.

 

If you were talking about replacing them with tensioned steel, how would that actually work? The vanes are one piece within a ring on the VC200l, so we'd lose the ring also (see OP photo).

 

It seems a shame that the vanes are just so thick. My Takahashi Epsilon in similarly rugged in holding collimation, but with beautifully thin spiders. I understand that they need to be that thick for casting, but as an autograph it seems an odd choice.

 

And Jon, were you offering your services or were you stating that "even I could do it" lol
 

[Jon Isaacs]

I won't argue with cold logic.

 

If you were talking about replacing them with tensioned steel, how would that actually work? The vanes are one piece within a ring on the VC200l, so we'd lose the ring also (see OP photo).

 

It seems a shame that the vanes are just so thick. My Takahashi Epsilon in similarly rugged in holding collimation, but with beautifully thin spiders. I understand that they need to be that thick for casting, but as an autograph it seems an odd choice.

 

And Jon, were you offering your services or were you stating that "even I could do it" lol
 

 

I'd have to see the actual assembly but my thinking is that I'd remove the existing vanes, sawing and grinding.. Drill holes in the upper  ring for threaded rods and attach the outer ends of the vanes similar to astro-systems spiders. 

 

I'd have to see how to connect the inner end.

 

Yes, I could do it but you wouldn't want me to do it. You have a very nice scope there... I was an engineer, not a machinist. My comment should be interpreted as:

 

"This so simple even an engineer could do it." 

 

Jon

[Tubuskahusk]

Astro-Systems secondary spiders and secondary holders are used in many Newtonians. The issue with the design is that the secondary holder is mounted using a central bolt which makes the quite tall. 

 

If the stock design attaches the spider to part of the secondary holder as the drawing suggests, there's not enough room, the secondary is too close to the primary.

 

Jon

 

 

Thanks for pointing that out Jon. I had no clue. 

 

Edited by Tubuskahusk, 04 October 2024 - 08:48 AM.

[LDW47]

I know several high end machinists who, upon retiring, built small shops in their garages to do the challenge work, the detailed jobs just to keep their hands in the industry. They love that, they would do it for practically nothing I am positive. I am sure they would take it on or at least give good advise and my feeling is it would be you are taking a real chance with no guarantees. Good Luck and maybe be happy with what you have.

[NinePlanets]

I very much recommend that you make a new ring, spider, and support and keep your current part as it is.

You are asking for trouble and heartache to thin the existing vanes and they will NEVER be as thin as you can make. I use 0.015" thick brass. I can guarantee no machinist is ever going to successfully make the existing vanes that thin.

[mrflib]

I very much recommend that you make a new ring, spider, and support and keep your current part as it is.

You are asking for trouble and heartache to thin the existing vanes and they will NEVER be as thin as you can make. I use 0.015" thick brass. I can guarantee no machinist is ever going to successfully make the existing vanes that thin.

Thanks all.  I will just get a whole new assembly made I guess.

 

What do I google, astronomy machinist UK or something? Nothing obvious comes up in the results; just large firms which I doubt would be interested.

[CowTipton]

Thanks all.  I will just get a whole new assembly made I guess.

 

What do I google, astronomy machinist UK or something? Nothing obvious comes up in the results; just large firms which I doubt would be interested.

Are there any industrial parks near you?

If yes, just find a smaller machining company, go inside and ask.  Worst they can say is no.

[havasman]

I'd use a 12" flat b@sta#d file. Configure good support for the vanes, work slowly and gently, and know when to quit. Be careful of the radius at the ends of the vanes. Files can be great precision tools for this kind of job.

[LDW47]

I'd use a 12" flat b@sta#d file. Configure good support for the vanes, work slowly and gently, and know when to quit. Be careful of the radius at the ends of the vanes. Files can be great precision tools for this kind of job.

Files are great but just one bad pass, too much pressure could easily cause a disaster. Thats why I mentioned emory cloth and not a light file and even then, it would be touch and go when the size gets right down. You have to have a precision feel like a long time precision machinist.

[Peds]

If you're handy with CAD work, you could upload your design to Xometry UK, JLC3DP or PCBWAY (China) for a CNC machined piece. They quote instantly and are usually quite good, but can be a bit spendier.

[mrflib]

If you're handy with CAD work, you could upload your design to Xometry UK, JLC3DP or PCBWAY (China) for a CNC machined piece. They quote instantly and are usually quite good, but can be a bit spendier.

This is actually great, I do CAD for work so I can make this work! I'll share the file here for other Vixen VC200L guys if it all works out.