The Marble Mantis is a new and unique design of Hot-Air engine designed and made in England*.
Often called Stirling engines after Robert Stirling,
the Scottish clergyman responsible for refining the
design in the early 19th century, they work by alternately
heating (expanding) and cooling (contracting) air within a cylinder
forcing a piston in and out. Unlike internal combustion engines which
ignite gasoline within the cylinder before expelling the exhaust gasses, Stirlings maintain a closed cycle with
the heat-source on the outside.
Hot air engines have seen a resurgence of interest in recent years and
are now being used for various green applications such as harvesting solar energy
using parabolic reflectors and generating cheap power from waste in third world countries.
NASA is currently developing technology to power deep space probes which uses Stirling engines
to harness the heat from small nuclear reactors. Eventually they plan
to use this principle on a larger scale to generate power for manned bases on the Moon and Mars.
The Marble Mantis arrives at your door in quick-build kit form. It's less likely to get
damaged in shipping and is fun to assemble!
All the fiddly, messy bits have been done, leaving you with a straight
forward nuts and bolts construction. No glueing is required and the whole assembly should take
no more than about 10 minutes to complete.
Everything you need is included in the kit except for a pair of pliers and the
methylated spirits fuel which you can buy in any hardware store or supermarket.
For those not used to following building instructions from plans I've made an easy-to-follow
instructional video (see above). It takes you through every step from unboxing through
construction and operation.
There is also a double-sided sheet of instructions in clear English included in the box. If you're curious you can
preview a PDF
Since making my first hot air engine out of tin cans and toy balloons a few years ago I have
become hopelessly addicted to designing and building these fascinating machines in my free time.
As I began to refine my building techniques I started trying to devise the very simplest methods
of harnessing the Stirling cycle to provide locomotion. The technical challenge was to
dispense with the complications of directly driven displacers, piston linkages and cranks yet still
somehow allow the engine to propel itself. The practical challenge, no less of a hurdle, was to
do everything in my tiny kitchen without any proper machine tools.
The Marble Mantis is the fruition of many months of painstaking trial and error. Starting with a spark of inspiration and
ending up, after much tearing of hair and gnashing of teeth, with a
machine that not only runs reliably but looks good enough to take pride of place on any display shelf.
I hope you enjoy owning the Marble Mantis as much as I enjoyed creating it.
Marek S-Hayward (BSc) Bedfordshire, England.
I only accept payment through Paypal.
Please make sure you have a valid Paypal account prior to bidding.
Please pay immediately on purchase.
All items will be shipped to your eBay address. Before you pay, please make sure your address in eBay matches the address you would like me to ship to.
Import duties, taxes and charges are not included in the item price or shipping charges. These charges are your responsibility. Please check with your country's customs before making your purchase.
I will put your Marble Mantis in the post within 2 business days of the payment being received.
Delivery Time: Generally, 1-2 days within the UK and 1-2 weeks to the rest of the world (Assuming no delay at customs).
I personally build each motor unit and test every one before packing it up so it is very unlikely that you will experience any problems.
In the event, however, that you discover a component has been damaged during shipping then please contact me
within 14 days of receipt and I will send a replacement part out to you.
If you have trouble getting the Marble Mantis to work and there is nothing obviously wrong with it, please contact me within 14 days of receipt and I will carry out a trouble shoot with you via email. In the unlikely
event that the problem can't be overcome I will send a replacement or, if you prefer, arrange a refund.
Return postage will be the responsibility of the buyer.
The glass components of the Marble Mantis are fragile and the likelihood of damage and wear is dependent on how the machine is treated. For this reason I do not offer a warranty.
However, if you find that you need a replacement part due to natural wear and tear then I can offer to sell you spares at a fair price.
Safety:
The glass engine gets very hot during use, never touch the glass tube after lighting the flame. Always allow at least 10 minutes to cool after extinguishing the flame before handling.
Once lit, never leave unattended. Do not run on or near flammable materials. To avoid potential overheating allow sufficient time to cool before refilling the spirit burner for another run.
This is not a child-safe toy. Children should be supervised at all times to avoid burns and risk of broken glass.
*Includes individual components sourced from USA and China.
