Can anyone build me a Stirling engine for a BBQ rotisserie?

Discussion on Stirling or "hot air" engines (all types)
JCal98
Posts: 2
Joined: Mon Mar 20, 2017 12:33 pm

Can anyone build me a Stirling engine for a BBQ rotisserie?

Postby JCal98 » Mon Mar 20, 2017 1:40 pm

I'm aware the idea isn't particularly new, but as part of a school project I am to build a rotisserie attachment powered by a Stirling engine to fit onto a Weber kettle style barbecue. The plans for the product as a whole are more or less complete, the only real issue left is the Stirling engine itself, I've searched for weeks and all the Stirling engines I've found online are too small and very expensive for what I intend to use it for.
Pretty much I need a Stirling engine that will fit into a space of around 100x250x350mm (dimensions can be adjusted if necessary) and for it to be able to be connected to a gear system to lower the RPM of the actual food skewer itself. It would need to be resistant of fairly high temperatures of course and the higher the RPM the better. The actual capabilities of the engine really don't have to be that impressive and it doesn't have to be pretty, just as long as it works to a degree.
I don't have very much engineering experience and as a student I don't have access to great excesses of funds, so if someone would be able to assist me in constructing such a Stirling engine or directing me to some relatively simple plans that I could use to construct one myself it would be much appreciated.
I live in the UK, I've got a couple of months to finish the project and if someone is willing to be as kind as to build one i would be more than happy to accommodate payment.

Many thanks.

Ian S C
Posts: 1983
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: Can anyone build me a Stirling engine for a BBQ rotisserie?

Postby Ian S C » Wed Mar 22, 2017 1:05 am

I'm a bit far away to be much help, but I wish you well. If this project is for school, do you have use of the school metal workshop, and a lathe?
This is a BETA type motor, that would power a barbecue, the power cylinder is 2 1/4/58 mm bore, and it has a power stroke of 1 1/4"/ 33 mm, and a displacer stroke of 1 3/4"/ 45 mm. The legs are cast iron and came off an old electric stove. The two flywheels are about 160 mm diameter and 24 mm across the rims.
Ian S C
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JCal98
Posts: 2
Joined: Mon Mar 20, 2017 12:33 pm

Re: Can anyone build me a Stirling engine for a BBQ rotisserie?

Postby JCal98 » Thu Mar 23, 2017 2:48 pm

Thanks anyway, yes I have got access to the school workshop however metal working is fairly limited but there is a lathe and welding facilities as well as rough cutting tools for thin metal sheets. I did forget to mention that the engine I'm looking for would be a beta type so thank you for showing me that particular example, I may have to build something similar if possible.

cbstirling2
Posts: 120
Joined: Sat Dec 17, 2016 9:35 pm

Re: Can anyone build me a Stirling engine for a BBQ rotisserie?

Postby cbstirling2 » Fri Mar 24, 2017 5:42 am

I know you said money is tight...
This engine is a gamma available for sale. $500 usd is too expensive imho, half that and I would buy it.g
http://www.ebay.com/itm/BIG-STIRLING-EN ... 1849838131
Originally this engine was meant for a fan and the lack of forced air will reduce the running time of this engine.

A trouble with beta engines is the difficulty in linkage and thermo isolation between the hot and the cold parts of the engine. An alpha V configuration is more efficient (construction and operation) and produces more power for the same cc than do other designs. Win win .
CBStirling2

Ian S C
Posts: 1983
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: Can anyone build me a Stirling engine for a BBQ rotisserie?

Postby Ian S C » Sat Mar 25, 2017 3:32 am

cbstirling2, there is a thread about the engine on ebay, there was some difficuly either with the motor or the manufacturer, it's probably about 6 or 8 pages back. For a professionally built engine I'd say its a bit rough, it's about the same size as the one in my photo above, you would be lucky to get a continuous 10 Watts out of it(they say 20 Watts).
Ian S C

Trevor
Posts: 171
Joined: Sun Nov 06, 2016 4:07 am

Re: Can anyone build me a Stirling engine for a BBQ rotisserie?

Postby Trevor » Sun Mar 26, 2017 2:42 am

Hi JCal
If you want to run a rotisserie for a barbecue you do not need much power.
A small well made Sterling engine will drive one with a pulley system (1:4 ratio) quite well. I do not believe you need anywhere near 10 Watts probably closer to 300mA would be more like it.
You could use the heat from the barbecue if the heating chamber is placed in sideways and then the drive work should work quite well with a mechanical belt drive and would be much cheaper to make. Also I think there was a thread on a barbecue with rotisserie around a month ago. If someone can remember it - Please let JCal know
Trev

cbstirling2
Posts: 120
Joined: Sat Dec 17, 2016 9:35 pm

Re: Can anyone build me a Stirling engine for a BBQ rotisserie?

Postby cbstirling2 » Sun Mar 26, 2017 5:01 pm

Watts vs amps? Are those two comparable? With Amps you need volts to get watts
CBStirling2

Ian S C
Posts: 1983
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: Can anyone build me a Stirling engine for a BBQ rotisserie?

Postby Ian S C » Mon Mar 27, 2017 3:25 am

Amps x Volts = Watts.
Ian S C

Trevor
Posts: 171
Joined: Sun Nov 06, 2016 4:07 am

Re: Can anyone build me a Stirling engine for a BBQ rotisserie?

Postby Trevor » Tue Mar 28, 2017 3:12 am

High CB - The voltage I normally talk about is 12VDC and/or 6VDC.
For small models 200 mA would be easily available and give the good results for a small Rotisserie. These can be obtained from good barbeque places and are available in 1.5VDC and 12VDC as well as 240VAC.
All in all we are talking about 2.4 Watts at 12VDC or 1.2 Watts at 6VDC
Trevor

Ian S C
Posts: 1983
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: Can anyone build me a Stirling engine for a BBQ rotisserie?

Postby Ian S C » Wed Mar 29, 2017 2:21 am

If needs be you can replace the bearings in the Rotisserie with ball races if the original ones are plain bearings, and try and keep the roast fairly well balanced so it rotates smoothly, with the speed reduction required, it will take very little to turn it. Years ago you used to be able to get a rotary spit that was operated by a falling weight (about a pound or two), I think it was usually set up to take about 10 minutes to fall, then you wound it up again, but this shows that very little power is required, the one I saw had a fair bit of friction in it's rusty screw thread, and unlubricated, worn bearings, It squeaked and squealed.
Ian S C


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