Test tube source for Jan Ridders coffee cup stirling

[RonP]

I live in New Zealand and am part way thro building this delightful model but looking for an appropriate source for the required test tube.
Maybe someone has a spare to sell or can advise where they are readily available. Thank you, Ron

 

[Herbiev]

Try Ebay. Several suppliers there.

 

[lensman57]

Hi,

I got the plans from Jan a couple of days ago and ordered some test tubes from eBay, I just hope that they turn out to be the correct size.

Regards,

A.G

 

[RonSkingley]

I'm just about to start building this too.

Emailed Jan for the plans today.
What size is the test tube?
So I can order one on eBay.

Ron
Ireland

 

[rleete]

Edmund's Scientific. US company, so shipping may be an issue, but they did have the correct sizes.

 

[lensman57]

I'm just about to start building this too.

Emailed Jan for the plans today.
What size is the test tube?
So I can order one on eBay.

Ron
Ireland

There was a thread and a reply from Jan, he said that the dimensions of the tubes are not so critical, i wish I could find the thread.

Regards and best wishes,

A.G

 

[RonP]

Greetings, Thank you all for your replies. The difficulty with some of the Ebay suppliers is that their test tubes might not meet the specifications required for the model to work successfully as Jan has explained. Earlier this month I received a reply from an enthusiastic Ebay supplier, but when I gave him the specs there was no further response from him!
It would be very helpful if we could receive advice/help from a modeller who has already sourced a suitable tube from Ebay, for when you look at the Ebay suppliers there are many, many of them. Can someone advise please - thank you.

 

[Longboy]

Right off the bat you do not need test tubes for a LTD type coffee cup engine! Its displacer cylinder can be made with plumbing PVC or clear plastic/arylic for the "view". For modeling Gamma and Beta Stirlings or the power cyl. in an LTD type, test tubes come in standard sizes by nominal millimeter diameters. Length is no issue cause you will be cutting to length for your model. The major consideration is that the glass be of PYREX by trademark or gerneric Borosilicate glass as it will be in the flame ( other than LTD). Nominal sizes are 16 and 20mm for a good scale Stirling engine. Stirling is very liberal in sizing and clearance consideration. You may in medium size citys and larger find a laboratory supply vender or take your plans to a university science department locally and see what they use and source from. You should be O.K. with an EBAY vender as long as the tubes are specified PYREX or equivalent.

 

[lensman57]

Hi LongBoy,

The ones that I have ordered from ebay are Pyrex, 18, 16 and 20 mm nomoinal sizes. I have a question though about the method of cutting these tubes. Would the scratch and heat method work for Pyrex tubes?


Regards,

A.G

 

[Tin Falcon]

Jan has a neat rig for doing it if you want to go tot the trouble of building
. I think his site explained simpler methods as well. and there are a few posts around here on the subject.
Tin

 

[RonSkingley]

Many thanks for the info.

Guess I'll order some standard I've tubes on eBay.
I've a friend who does all sorts of decorative cut and fused glass, and he has cutters and grinders, so will ask him if he can cut Pyrex test tubes.

 

[RonSkingley]

There's plastic test tubes available too.

Might be ideal for the displacer, and a lot cheaper and easy to cut (I assume?).

 

[Longboy]

I cut my tubes on the lathe. Masking tape on the closed end in the jaws and with a diamond impregnated file kit, hold to the tube as it grinds a grove into the glass. Some brands of tube cut nice and others tend to fracture. Depends on wall thickness and your patients. You can clean up a jagged split holding tube to a bench grinder to square up the cut end. Other hobbiests have used a Dremel tool with a thin grit wheel with good results. Heating the tube to cut can soften enough to help prevent fracture but only when tube used as a displacer cylinder. Forget it if cutting for use as a power cyl. as distortion eliminates any perfect roundness needed here as a power cyl. You will also find that a 16mm tube inserted into the 20mm gives you enough clearance for a displacer cyl and piston combo but note depending on brands used there can be nearly a .020inch difference in diameters of these test tubes.....pretty "nominal"! For your Coffee Engine power cyl. I would stay with a metal cylinder over glass. test tubes seem to be the "roundest" somewhere in the middle to match with graphite piston to seal the best. Glass can be tricky and time consuming creating a match set in using as a power cylinder/ Graphite piston in Stirling in my experiance. I have 3 Gamma Stirlings using a test tube displacer piston. Follow my videos on Youtube! One other tip in procurring a 3 or 4 inch dia. clear plastic displacer cylinder for you Coffee engine is to visit a hobby/crafting retail store. We have "Michaels" and "Hobby Lobby" nationally in the USA.

 

[Chriske]

Testtube low rpm, diamond cutter high rpm, use water to avoid shattering of testtube

 

[RonP]

Hi Guys, thank you all for your replies. But I have to make a sincere apology - I have been referring to Jan's "Coffee cup Stirling" when in fact I should have been referring to the "Thermo Pulse Mobile."
Yes, it is the test tube for the "Thermo Pulse" and NOT the Coffee Cup (that has NO test tube!!) that requires the tight specs and the difficulty to source!! Oh dear, the Christmas celebrations and the hot sun down here have got to me and created that confusion - so very sorry about that!!! :hDe:
So to recap, can anyone advise where to source the test tube for Jan's "Thermo Pulse Mobile?"

Thanks heaps guys, I appreciate your help and advice,
Cheers' now with a clear head!!!
Ron

 

[messe]

Has anyone ever used the glass tubing cutter from McMaster- Carr. Any info. will help
Mike