Unipower and Leonides questions

We are pretty good at answering car related questions, but even with the help of ex-Alvis employees we were not able to answer the following two questions – can you help?

From Keith Roberts:

Q. Having long been an enthusiast of Alvis military vehicles I was pleased to find your web page. My interest falls between automobiles and the armoured vehicles of Alvis, to be exact my interest relates to the Alvis-Unipower trucks. Do you have records related to the MH-660 or MH-8875 trucks produced in the 1990s and if not, can you suggest where such information may exist? Many thanks for any help you can give.

A. Martin Wickham says the design work was done by Unipower at their Greenford site and they were built in the Walsgrave factory. The vehicles went into service with the Royal Engineers, and their museum at Chatham may well be the place to seek further information. We will ask our Followers if they have any information on these vehicles.

Neil Millington found this link to Unipower history

Also…..

From: John Hay-Heddle

Something over 50 years ago I read an article in “Autocar” I think. It was about the work of an emigre French aerodynamicist who came to Britain in WWII to escape the Nazis. He had a theory about using a specially designed exhaust system to boost the power and fuel efficiency of aero engines. The Government was sufficiently interested as to allot him an ALVIS LEONIDES engine to experiment with. He designed and kitted it out with tuned exhaust pipes – one for each cylinder – which looked very like those designed by Walter Kaaden for racing 2 stroke motorcycles. The article reported that he obtained a 10% or better increase in power output and an approximately equal improvement in fuel efficiency.

At the time of the work described and of the writing of the article, there were no electronic aids to perform the calculations needed, nor to test the results of these calculations.  The calculations had to be performed with pencil and paper using slide-rule and log-tables, aided and abetted by blood, toil, tears and sweat and many gallons of midnight oil.

Eventually, satisfied that his calculations, he made up his prototype system.  For the 9 cylinder engine it required nine separate exhaust pipes.  Because this was difficult, time consuming and expensive, and because there was no means of performing mathematical modelling of the interplay between all the salient dimensions, the resulting pipes were all built like trombones; adjustable in all salient dimensions.  For weeks, if not months, he carefully adjusted all the dimensions against each other and recorded the results until he came up with an optimised set of dimensions.

These produced: –

1. A useful (10% from memory?) increase in power output
2. A useful reduction in fuel consumption per unit of power produced (again about 10% from memory.) In other words one got an extra 65 BHP from the same fuel consumption as observed in the unmodified engine.
3. A stunning reduction in noise level.  It was reported that with the motor running at full power one could easily hear the tappets working.  This would have been immensely useful if used on an aircraft like the Westland Lysander employed for inserting and evacuating S.O.E. operatives into and out of occupied France.

What then happened bordered on farce.  He reported his findings to the Ministry who sent assessors down to examine his system.  It seems that, not being content simply to test his optimised set-up, they insisted on playing with the adjustability of the dimensions.  The result was that they so stuffed the operation of the motor that it simply would not run!  Our Frenchman then berated them in lurid French – “Vous foux, imbecilles Anglais” being among the more repeatable terms of abuse he used for their stupidity – and he stormed out “In a truly Gallic huff!”  (The words in quotes are exactly as used in the article.)

What subsequently happened to the Frenchman and his work is unclear, except that the latter was never acted upon.  That is until Walter Kaaden independently resurrected his work 20 years later for use on racing two-stroke motorcycles.

I think you will agree it is a fascinating story, and worth the while of the Alvis Archive to resurrect if you can find it.  Please feel free to edit my account and add it to the archive as an un-documented recollection – even though I can personally vouch for the accuracy of the general thrust of the story as a retired research scientist.

Author: alvisarchive

Driving Alvis cars since 1964 and the website since 2012 View all posts by alvisarchive