Search found 9 matches

by Rog Tallbloke
Fri Jan 23, 2015 8:50 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: My observation on home built strings.
Replies: 22
Views: 7911

Re: My observation on home built strings.

Most of the prototypes I see on youtube use quite shocking amounts of gas to get rpms. This because at higher rpms, lots of heat is needed to pump energy into the displacer cyclinder fast enough. As well as wasting expensive propane, it makes a racket. I'm going to try to make something which runs o...
by Rog Tallbloke
Fri Jan 23, 2015 5:21 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: My observation on home built strings.
Replies: 22
Views: 7911

Re: My observation on home built strings.

Thermal Conductivity of stainless 8.1 (Btu/(hr-ft-F))
Thermal Conductivity of copper 231 (Btu/(hr-ft-F))

So if rigidity is the issue, an exoskeleton of titanium wire supporting a corrugated copper cup has to be worth a try, no?
by Rog Tallbloke
Fri Jan 23, 2015 5:08 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Stirling Engine Thermodynamics
Replies: 75
Views: 33257

Re: Stirling Engine Thermodynamics

That's interesting Ian. It indicates that the longer dwell of the working gas at the cold end when the engine slows under load has a bigger effect than the longer dwell of the working gas at the hot end. I wonder if it would be a different story in a pressurised engine, where there is greater molecu...
by Rog Tallbloke
Thu Jan 22, 2015 7:44 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Stirling Engine Thermodynamics
Replies: 75
Views: 33257

Re: Stirling Engine Thermodynamics

Aviator, I didn't say slowing the engine down would increase the power, I said "As the engine slows, the working gas spends longer in contact with the hot end of the system and reaches a higher temperature", though as you correctly say, there will always be a gradient through the system. There may b...
by Rog Tallbloke
Thu Jan 22, 2015 5:42 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: My observation on home built strings.
Replies: 22
Views: 7911

Re: My observation on home built strings.

Ian, would I be right in thinking that there will always be positive pressure in the hot cyclinder, even in an unpressurised stirling engine? I ask because I'm wondering about a much cheaper solution for a small (5W) machine involving pre-corrugated copper sheet. i.e. If an external support lattice ...
by Rog Tallbloke
Thu Jan 22, 2015 12:40 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Stirling Engine Thermodynamics
Replies: 75
Views: 33257

Re: Stirling Engine Thermodynamics

I'm a newbie here, and so very late to this debate. I'd just like to add a couple of points which I hope will help. If I understand correctly, Tom's hypothesis is that when the engine is under load, more energy is dissipated in converting thermal energy to kinetic energy, and so less energy is neede...
by Rog Tallbloke
Wed Jan 21, 2015 2:10 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Website Links Area and Magazine Articles..
Replies: 71
Views: 47675

Re: Stirling Engine magazine articles..

I found Andy Ross' book 'Making Stirling Engines' Available here: https://docs.google.com/file/d/0B_t-6mP ... edit?pli=1:
by Rog Tallbloke
Wed Jan 21, 2015 12:32 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: My observation on home built strings.
Replies: 22
Views: 7911

Re: My observation on home built strings.

Hi guys, I'm a newbie here, so forgive me if it's been covered. Has anyone had the hot cap off a sunpower free piston unit to see what it's like inside? One aspect of heat transfer is material thickness. Won't there be a trade-off at some point between finning and mass? Clearly the better the therma...
by Rog Tallbloke
Wed Jan 21, 2015 11:12 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: "Hi...We are new here!" First posts here (or anywhere is OK)
Replies: 437
Views: 137807

Re: "Hi" We are new here!

Hi all,
I've built a couple of pop can stirling engines and want to try something more ambitious that has a practical application.
I'm an engineer by trade and like motorcycle camping in my summer free time.