Standard Test Bed Shell

[OldSpook]

@WobblyHand has been kicking around the idea of a moderator "chassie" to use when developing baffles so that less printing is involved and you can compare apples to apples on the test range.

It is a great idea. I have one in work. When I have something good enough to put out to everyone I'll link it here and update the last post in the thread to bump it to Top Of Page.

 

[denovich]

I like the pragmatic choice to make the caps hex shaped so they are easy to twist on/off. No reason to worry about aesthetics for a test article.

 

[beerthief]

great idea for testing , uniformity in the size of the moderator . To my way of thinking this would be the way to test baffle design's . Apples to apples !
Maybe several test length 's to test @ 2,3,4, 7? baffle's .

 

[beerthief]

addition to post #3 . ALL participants using the same size and material shell . just to clarify .

 

[WobblyHand]

Hmm, been there, done that
Yesterday, in fact. Didn't use a hex though, used a pin spanner instead for a cleaner look. In fact, @OldSpook this is one of your designs... Gyroid PETG, Gyroid TPU & Solid TPU. But I do like the fact that the threaded sections shown above mate to the flat of the tube for registration, that's better than what I did. FYI boys and girls, those are functional 32 TPI threads on both ends of the tube. You'd probably be better off with coarser ones, but these work if you use silicone oil.

 

[OldSpook]

Hmm, been there, done that
Yesterday, in fact. Didn't use a hex though, used a pin spanner instead for a cleaner look. In fact, @OldSpook this is one of your designs... Gyroid PETG, Gyroid TPU & Solid TPU. But I do like the fact that the threaded sections shown above mate to the flat of the tube for registration, that's better than what I did. FYI boys and girls, those are functional 32 TPI threads on both ends of the tube. You'd probably be better off with coarser ones, but these work if you use silicone oil.
View attachment 431061

I should have said that I stole the idea from you because I did. Sometimes I forget that we are not all on the same page.

 

[WobblyHand]

I should have said that I stole the idea from you because I did. Sometimes I think everybody's reading everything that I read.

I know you did... An acknowledgement is always appreciated, even if borrowing ideas. Moving right along.

Think you are on the right track with making the threaded piece register to the tube. That gets the flat face perpendicular to the bore. I do think this rig will be good for testing. A pin spanner is more elegant than a big old hex, but I do realize that most can't just make custom ones with an arbor press. I had to make a lot of custom pin spanners to service my PP700SA recently, so using a pin spanner came naturally to me. The PP used an awful lot of them, and I had none. They aren't too hard to make, once you get the sizes right. Finding a 1.95mm drill that didn't drill oversized was the hard part. 2mm pins pressed into a 1.95mm hole.

 

[OldSpook]

I know you did... An acknowledgement is always appreciated, even if borrowing ideas. Moving right along.

Think you are on the right track with making the threaded piece register to the tube. That gets the flat face perpendicular to the bore. I do think this rig will be good for testing. A pin spanner is more elegant than a big old hex, but I do realize that most can't just make custom ones with an arbor press. I had to make a lot of custom pin spanners to service my PP700SA recently, so using a pin spanner came naturally to me. The PP used an awful lot of them, and I had none. They aren't too hard to make, once you get the sizes right. Finding a 1.95mm drill that didn't drill oversized was the hard part. 2mm pins pressed into a 1.95mm hole.
View attachment 431120

Yeah, the drawing was more of quick hack that I had hoped someone might pick up and run with. I had range safety duty today so was not around the forum or desktop. I've refined the drawings above a little and I'll print one this evening to do fit-up. Once I have that I'll drop some stl files here.

 

[WobblyHand]

Yeah, the drawing was more of quick hack that I had hoped someone might pick up and run with. I had range safety duty today so was not around the forum or desktop. I've refined the drawings above a little and I'll print one this evening to do fit-up. Once I have that I'll drop some stl files here.

It's better that you boosted the ID of the tube. Found 28mm to be a bit limiting for some designs, 33mm is a little easier to fit things in.

33mm is a odd ID for CF tubing. I like to get 1.5mm or 2mm wall tubing so I can thread it, can't seem to find any CF at 36/33 mm, or for that matter 37/33. I found some 40/37 that you can get, but that's getting a little wide. Also saw some 35/32, but not 36/32. Guess the question really is, do you have some source for CF tubing with that ID and reasonable OD's, or is this thinking too far ahead?

 

[OldSpook]

It's better that you boosted the ID of the tube. Found 28mm to be a bit limiting for some designs, 33mm is a little easier to fit things in.

33mm is a odd ID for CF tubing. I like to get 1.5mm or 2mm wall tubing so I can thread it, can't seem to find any CF at 36/33 mm, or for that matter 37/33. I found some 40/37 that you can get, but that's getting a little wide. Also saw some 35/32, but not 36/32. Guess the question really is, do you have some source for CF tubing with that ID and reasonable OD's, or is this thinking too far ahead?

All that is configured in the code. Once the code is done I can run off a complete set of stls for any diameter and/or length in about five minutes.

I picked 33 because I use 35/33 to build the Ember design which the guys seem to like.

Any size you want.

 

[WobblyHand]

All that is configured in the code. Once the code is done I can run off a complete set of stls for any diameter and/or length in about five minutes.

I picked 33 because I use 35/33 to build the Ember design which the guys seem to like.

Any size you want.View attachment 431151

1mm wall is fine to glue, but tough to thread. I'll be patient. 35mm is a good OD, not too big, and I can see why it is a popular size. I might hack about in FreeCAD and see if I can set up a parameterized model, would make my life easier.

 

[OldSpook]

I know you did... An acknowledgement is always appreciated, even if borrowing ideas. Moving right along.

First post fixed.

 

[OldSpook]

I've just attached the stl files to the top post.