Craig's LTD Stirlings

New 3/20/99

A few days back we received an email from Craig with an attached photo of four LTD Stirling engines. he noted that he was just a beginner, but from the look of the engines, certainly a skilled one. Our interest piqued, we wrote back for more information, and possible a few closer photos of the engines. The very next day we had a reply, and photos of the engines individually.

Craig's first email asked for advice on constructing a concentric engine similar to our Test Tube Rhombic, but withour the rhombic drive. He attached the following photo, with the comment "I am quite proud of the fact that some of my LTD engines work on as low as 5 degrees f. temp difference. " I think you will agree that he is justly proud.

On sending the photos you will see below, Craig commented: "I have not really tried to make my engines attractive, I was just tring to make the mechanicals work properly (chrome won't get you home, but candy sure is dandy!)"

"My interest in stirling engines has cause me to purchase two lathes, lots of tooling, and books. I am an auto tech by trade, the only thing I ever machined were brake rotors and drums, so the learning curve has been pretty vertical. However, I read all I can. My very first LTD was made by looking at one on the internet, home made graphite piston, brass cylinder, cut from the tube of a heater core, the displacer chamber was cut from a gravy separator, the plates were from old computer hard drive cases. "

"I then bought Dr. Senft's book, and kit from BCS, and this engine ran better. Most all of the hardware is old computer stuff modified to work, plus all the good ball bearings found in them. But I want to build a concentric engine, so that is the next step, after I find the stuff(recycled of course) to build it, and study the design more. "

" I am little concerned about how I feel towards these engines, I feel a little obsessed. " (we know the feeling exactly!)

In a later communique, Craig, at our request, gave some biographical information:

"I live in Tulsa Oklahoma, and have been an auto tech for 22 years, and have been building these LTD engines for about 2-1/2 months. As I said before, these things have caused me to want to learn machine work, and I have purchased 2 lathes (a mini, and a 9x20 quick change) with the hopes of buying a milling machine someday. I have become obsessed with these things, I can not stop thinking about them!! I keep them on my tv set and 'puter monitor. One I kept running for 2 weeks just to see if it would, I maintained about a 10 deg. diff. for it (1 single christmas lamp bulb) speed was about 50 rpm at this temp."

"As you could see from the photos, they are all different sizes. This was to see how the sizes effectedperformance, etc. The very small one is kinda funny it likes hot water, and will spin what seems like about 300+ rpm!, but won't run at low temps. I have small leak at the displacer tube that I think is the problem. It will run about 15 min on a small foam cup of very hot water. The others all have different personalities, but all will run at 15 deg. f. or less temp differences. Some have regenerators, some not."

"I would like to build a Beta engine (I mistakenly referred to it as an alpha). a concentric engine, both pistons in same cyl. , I like this design, although I know it may be easier to build a different type. I also like the ringbom engines, and am amazed at what the two of you have made!! I try to teach myself all I can without going to formal schools, and this is probably not the route to take. My mathematics is not so good and am not sure how to get better other than keep working. I plan on going to the Stirling show in August, can't wait!"

Well, we hope to go to Lake Itasca, too, and maybe we will be able to see Craig there. Herewith are the photos that Craig sent along. They are beauties, and certainly engines that any of us could be proud to exhibit. As always, click on the small images for a larger view. (this goes for the small photo above, too.)

The last two photos are the same engine, just the two sides.