24 replies to this topic

[rfiol]

I am thinking about using SendCutSend.com to cut custom-designed spider vanes from Stainless Steel for a 12" f/4.  They offer .8mm and 1.2mm thickness.  Here's a complete list:

 

https://sendcutsend....tainless-steel/

 

They also have other metals/materials:

 

https://sendcutsend.com/materials/

 

 

Questions:

1- Is stainless the way to go?

2- Is .8mm the way to go?

3- Is 42 really the answer to the ultimate question of life, the universe, and everything?

 

 

Edited by rfiol, 23 February 2021 - 10:12 AM.

[jmillsbss]

Pretty darn sexy!

[starcanoe]

Musk is a looker as well..

[daveco2]

Stainless should be called stain-less.  In my experience, it still stains; and it has strange fatigue properties.

Titanium, on the other hand, doesn't stain and has a higher strength to weight ratio. 

Maybe more importantly, titanium has half the thermal expansion coefficient of stainless.

[JamesDuffey]

 

Questions:

1- Is stainless the way to go?

2- Is .8mm the way to go?

3- Is 42 really the answer to the ultimate question of life, the universe, and everything?

 

 

N12F4.01.002-v27.jpg

The answer to 3 is 42, obviously.

[MitchAlsup]

Why so thick?

 

The vanes in my 13" F/3 and my 20" F/4 are both 0.007,8 thick (0.19mm) !!

 

Why make the spikes 4× brighter than necessary ?

[rfiol]

The vanes in my 13" F/3 and my 20" F/4 are both 0.007,8 thick (0.19mm) !!

 

Wires?

[Pierre Lemay]

Why so thick?

 

The vanes in my 13" F/3 and my 20" F/4 are both 0.007,8 thick (0.19mm) !!

 

Why make the spikes 4× brighter than necessary ?

I agree with Mitch. The new vanes on my 20" f/3.9 are also much thinner: 0.010" stainless steel. To make them I used this shim stock from McMaster-Carr. It was easy to cut with metal cutting scissors. I could drill holes to lighten further but the gain is not worth it.

 

Wires?

It can be done but I prefer solid vanes. Oberon's thread on spider supports shows vanes to be generally more robust than wires.

[MitchAlsup]

Wires?

When I tried wire spiders, the wires needed to be at least 0.013"-0.015" to have enough strength*--almost 2× the thickness of the vanes I am getting away with. I tried the thinner wires and it just did not work.

 

(*) strength in the "hold the secondary at all altitudes" and remain collimated.

 

When I went to 0.007,8" vanes (after flat black spray paint) I never had another collimation issue traced back to the spider or secondary. Others have had success with wire spiders, I salute them.

[MitchAlsup]

It can be done but I prefer solid vanes. Oberon's thread on spider supports shows vanes to be generally more robust than wires.

And Oberon did not even investigate thin triangular vanes 2-points at the secondary, 1-point at the UTA;

which appears much stiffer than a fat vane of equal height over its whole run. {And the vanes still won!}

[Adam Long]

I've tried 0.2mm Titanium on my current build but it won't stay flat. Might have to go thicker, the 0.3mm brass I used on the 10" was fine.

[BGRE]

Stainless should be called stain-less.  In my experience, it still stains; and it has strange fatigue properties.
Titanium, on the other hand, doesn't stain and has a higher strength to weight ratio. 
Maybe more importantly, titanium has half the thermal expansion coefficient of stainless.

The thermal expansion of stainless depends on the type of stainless. Austenetic grades (300 series) have relatively high thermal expansion martensitic grades (416, 420 17-4PH etc) have much lower thermal expansion.
Matching the vane TCE to that of the ring helps maintain centering, tension, etc., during temperature fluctuations.

[gregj888]

The answer to 3 is 42, obviously.

Don't forget that's base 13, it's important.

[MitchAlsup]

I've tried 0.2mm Titanium on my current build but it won't stay flat. Might have to go thicker, the 0.3mm brass I used on the 10" was fine.

Why do you need them flat--that is the job of tension !

 

My vanes curve a full 20º over their 8" length untensioned, but are better than a few thou when tensioned.

[MitchAlsup]

Don't forget that's base 13, it's important.

Remember the answer is 6×9 where the product is expressed in base 13.

[luxo II]

Stainless should be called stain-less.  In my experience, it still stains; and it has strange fatigue properties.

Depends on the grade. 301, 302, 308 do stain fairly easily, and 321 maybe. 316, no. But RK65 or 904L - definitely wont stain within the life of the Universe though cutting is another matter as these are very difficult to work with.

Edited by luxo II, 23 February 2021 - 10:22 PM.

[Adam Long]

Why do you need them flat--that is the job of tension !

 

My vanes curve a full 20º over their 8" length untensioned, but are better than a few thou when tensioned.

Top to bottom. I suppose i should have centred the bolts more precisely.

[MitchAlsup]

Top to bottom. I suppose i should have centred the bolts more precisely.

I clamped the UTA to my table saw and then clamped the secondary holder to the table saw at its proper position and at exactly 90º in order to eliminate that kind of error.

 

 

Then I made the vanes to fit the already precisely aligned parts.

[macona]

Another option is oshcut.com, I used them last year to cut a new front panel for my cnc mill. Fast service and good pricing.

 

20200912-47751E9F-EED3-4284-832F-D5D0B5F45444 by Jerry Biehler, on Flickr

 

20200928-21B21B7F-EA75-4A6E-9709-8269863CE655 by Jerry Biehler, on Flickr

[Oberon]

I am thinking about using SendCutSend.com to cut custom-designed spider vanes from Stainless Steel for a 12" f/4.  They offer .8mm and 1.2mm thickness.  Here's a complete list:

 

https://sendcutsend....tainless-steel/

 

They also have other metals/materials:

 

https://sendcutsend.com/materials/

 

 

Questions:

1- Is stainless the way to go?

2- Is .8mm the way to go?

3- Is 42 really the answer to the ultimate question of life, the universe, and everything?

 

 

N12F4.01.002-v27.jpg

Nice! But do look around for thinner material. I’m using 0.2mm which is more than thick enough.

[rfiol]

Another option is oshcut.com, I used them last year to cut a new front panel for my cnc mill. Fast service and good pricing.

Good tip.  I just checked and they have 316 Stainless Shim Stock in a variety of thicknesses.  I think I'll try the 0.254mm (0.01").  Each vane will cost $11.23 but there is also an $18 setup fee.  Not too bad.

[starcanoe]

Sounds good to me too !

 

I had some stainless steel rope climbing gear I was trying to modify (don't worry it was a safe modifcation). All I had to do was do a 3 linear cuts of about a 1 inch length on some plate about 1/8 inch thick. And drill 6 1/8 diameter holes. I got a new hack saw blade and drill bits just to do that. Went slow speed with the drill and used some oil for both cutting and drilling. Things started okay but went down hill fast as progress ground to a virtual halt very quickly. I switched to new blades and bits...again...the same thing and it seemed even WORSE. It took me an absurded amount of time to get it all done.

 

What I didn't realize at the time was that the stainless was working/heat hardening. And you didn't even need to actually get any detectable amount of the part hot. All that was needed was getting a very tiny bit of the metal hot right where the action was. Once that happened....you had a very hard part to cut or drill through..which made progress even slower and heat production even greater...a run away process once it got started...and it didn't take much to get it started apparently.

 

Lesson learned!

[Jon Isaacs]

Stainless should be called stain-less.  In my experience, it still stains; and it has strange fatigue properties.

Titanium, on the other hand, doesn't stain and has a higher strength to weight ratio. 

Maybe more importantly, titanium has half the thermal expansion coefficient of stainless.

 

Strength to weight isn't the important factor, stiffness to thickness is what's important and for a given thickness, steel is about 50% stiffer.

 

It can also be stronger depending on the alloy chosen.

 

I don't see stainless as an advantage over steel.. steel is easier to paint if that's your preference and can be plenty strong.  It's also easier to weld and braze.  

 

Jon

[BGRE]

Sounds good to me too !
 
I had some stainless steel rope climbing gear I was trying to modify (don't worry it was a safe modifcation). All I had to do was do a 3 linear cuts of about a 1 inch length on some plate about 1/8 inch thick. And drill 6 1/8 diameter holes. I got a new hack saw blade and drill bits just to do that. Went slow speed with the drill and used some oil for both cutting and drilling. Things started okay but went down hill fast as progress ground to a virtual halt very quickly. I switched to new blades and bits...again...the same thing and it seemed even WORSE. It took me an absurded amount of time to get it all done.
 
What I didn't realize at the time was that the stainless was working/heat hardening. And you didn't even need to actually get any detectable amount of the part hot. All that was needed was getting a very tiny bit of the metal hot right where the action was. Once that happened....you had a very hard part to cut or drill through..which made progress even slower and heat production even greater...a run away process once it got started...and it didn't take much to get it started apparently.
 
Lesson learned!

Stainless should be drilled with high feed and relatively high rpm.
about 1200 rpm and at least 10mm/minute for a 1/8" HSS jobber drill.
Coolant and a rigid setup may be required.

With the right feeds/speeds and coolant together with a suitable drill drilling stainless is easy.
Never stop feeding the drill or work hardening occurs.

Edited by BGRE, Yesterday, 05:40 PM.

[TopherTheME]

Answers:

1- Yes, unless you want to shell out the big bucks for Nickel or Titanium (not worth it IMO). I would go with 304 personally instead of 316 but I'm a cheapskate. 

2- A bit on the thick side, but it will work. I'd recommend 0.3-0.5mm

3- No, the answer to everything is more telescopes. 

 

When it comes to stainless, yes it can be a royal pain to cut. If you're going to do any cutting try to use 303 if possible, its one of easiest to machine with the higher sulfur content. As state above SS work hardens to you absolutely must have a high enough chip load and no dwelling unless you like dull tools. 

Edited by TopherTheME, Yesterday, 10:47 PM.