Model Engine Gallery Page 3

Click on the images to view them larger size.

More progress by Brian Perkins on his Bristol Hydra scale replica. The top photo shows the cam shaft drive to the four cylinder banks. The banks comprise four in-line cylinders with single overhead cams, disposed at 90 degrees around the crankshaft. Here we see the way drive is taken from the crankshaft to run the inlet and exhaust cams for each cylinder bank. Brian says the drive was assembled after a few problems with clashing teeth, which I can well imagine! All gears in the Hydra are 48 DP, which gives a rather small tooth profile. And look at all those tiny little holes around the periphery of the case cover that will have to mate up with equally tiny studs.

The next two show the magneto drive gears. Fully functional magnetos at scale model sizes pose difficulties getting enough magnetic flux to "cut" enough coil turns to generate a sufficiently large spark. Brian has approached the problem by using rare-earth (neodymium) magnets and running the mags at geared up speed. This is possible because the distributors are separate from the mags on the Hydra, unlike those on his earlier Bristol Aquila where mag and distributor shared a common body.

The Last shot shows the parts that go into those cylinder banks. For a description, see the October Model Engine News page.

More photos of the Hydra are available here.

Here's yet another magnificent example of craftsmanship from Les Stone. It's a 1/4 scale DeHavilland Gypsy 1 from Chenery plans and castings. Les did not say a lot about the engine in the email that accompanied the picture, but did confess that it runs, runs well, and that the task of cleaning up the engine after running is more than justified by the sound it makes. Thanks Les. Outstanding.
These pictures came were emailed in by Harvey Huisenfeldt who hales from Houston, Texas. They show his free-lance twin ball-race, glow ignition, rear rotor, .29 cuin racing engine. Here's Harv's own words:

Some background: Still working as Senior Production Engineer for Oceaneering Space Systems, a NASA subcontractor. Currently working on "Back to Flight" programs, including on-orbit repair scenarios for RCC (reinforced Carbon-Carbon) wing leading edge.

The engine was modelled after a 1950 McCoy .29 Red Head, which I'm restoring. Timing & porting is identical to the original. In order to machine the transfer port, I split the crankcase at the mounting lugs, as you can tell from the pictures. I've never seen an example of this, but I'd appreciate your thoughts. I've designed a lot of electro-mechanical projects, but this is my first attempt at machining. Materials are as follows: Aluminum 6061-T6, cast iron piston, crankshaft 1144 Stressproof, cylinder 41L40, wrist pin drill rod. Bore .670", stroke .754". I don't have a rotary table, so I machined the radial grooves on the prop driver using my swivel vise and a carbide engraving tool. I'll fire it up this winter to see if it runs. I'm up-dating the drawing package (Autocad) to reflect "As-built" configuration, but most of the design worked as drawn.

Next project is a Glow plug version of the "little Dragon", should go faster due to smaller scale. Incidentally, named my engine the "Viking" in honor of my Swedish mother who passed away last year at 96.

I'd be honored if you'd show the photos on your website, I'd be happy to share details with any interested craftsmen. I appreciate your assistance, let you know how the Dragon turns out. Thanks,

Harv Huisenfeldt
3734 Murworth Drive
Houston, TX 77025

This selection came from Bob Palfrey. It shows some engines made by Bob and some by his friends over the years. Reading from top to botton, we see:
  1. The Sky Angel 36 (front)
  2. The Sky Angel 36 (left)
  3. Bobco (left)
  4. Bobco (right)
  5. Book (left)
  6. Book (rear right)
  7. Hall (left)
  8. Hall (right)
  9. Tedco
  10. An array of Thors
  11. The George G Titan

Bob has been having a grand time anodizing crankcases with some outstanding and unexpected results. For example the delightful copper color on the Sky Angel (an ECJ project) came out of a scarlet bath! I'll let Bob describe his engines:

The first two pictures are of the Sky Angel .36 (the one Tim is going to publish) It a lapped piston, double ball bearing engine, starts and runs well, patterned after Ira Hassads Sky Devil with some liberties and ideas of my own thrown in.

The third and fourth pictures are the Bobco 65, again strong Hassad influence but all parts except bearings, bolts and plug shop made, it is .65 CID, ringed (2 rings) double ball bearing runs very strongly, easy to start.

Then we have the Book 60, designed to use McCoy parts, cylinder, piston, rings, rod, and crankshaft. It was designed for Al Book for use in tether cars. It is a very strong runner, not proven in a car yet but soon to be, I built this example and it is not finished yet but two others have been built and run.

Pics seven and eight show the Hall VDT (Vector Directed Turbulence) this example built by Mr. John Hall for whom it was designed, also for tether car racing, displayed and ran the engine at the MECA annual collecto this year. John used a K&B piston and sleeve and perhaps some other parts but it is a very fine running engine, single ring, chrome cylinder, dual ball bearings, rear rotary valve. It has not been proven in a car yet but one is under construction for it.

Number nine is the TEDCO 65, a Sky Devil that looks like the picture Edco used in their advertising. Ted made a new crankcase for the engine, had it anodized red and used all Sky Devil parts to make the engine.

Next are 4 of my "Thor" engines, there is a 5th but it is occupied at the moment in a U control plane! (probably the worlds only U control powered by a Thor). On the left is an almost true Thor, except that it has a steel sleeve and rings on the piston. It runs - weakly but it does run. Next is the "Black Thor" I tried to anodize the case and it came out a pukey olive drab color so I just painted the sucker black! Steel cylinder, lapped piston, front rotary valve, runs well. Next is the "Thorpus" actually a Campus 29 built on a Thor crankcase steel cylinder, CI lapped piston, it runs like the original, well. The last one is a Thor Rear Rotor Valve, steel cylinder, lapped CI piston and a delrin rotor valve, It is the strongest of these 4. All of the Thors except #1 have bronze crankshaft bushings.

Finally we have the Titan. This is basically George Genevro's engine but I made minor changes in the casting besides adding the beam mounts. It runs well and is easy to start.

This has been fun, I have more engines!

Cheers for now, Bob

These photos were sent to me in October 2003 from Kevin Wils. About a year ago, Kevin bought a set of M5 plans from an eBay auction. Noticing that some details of the cylinder had gone missing in the copy process, a web search led him to my pages and I was able to supply this missing information. Kevin said that he was planning on investigating the feasibility of making the parts from solid using CNC, just for fun (he is a professional in this area). I'd forgotten about it until this arrived:


I last communicated with you, I believe last year. I said I was making some progress on the manufacture of the engine from solid. Well, after a lot of CAD work ( creating models from the original prints) and lots of fixture building, here are some photos of my finished products. You can see that the cylinders were the most time consuming! The other parts, with the exception of the rocker arms, were not too much trouble (especially on a CNC mill!) I hope all is well with you "down unda in Australia". I hope you enjoy the photos, and I always like to share my work with others who appreciate what it takes to make things from scratch. I have built enough parts for two engines, and after a few more parts that I have to make on a lathe, I will buy the distributors, carbies, valve spring retainers, and other stuff I need from Vernal Engineering.

Motor Boy Ken Croft in the UK has a very talented neighbour named Tom Pasco, who also happen to enjoy the spot of model engineering, preferably with an added element of challenge—sufficient challenge to make me feel underqualified for basic basket weaving. We've seen some of Tom's efforts here before, but this time, he has really raised the bar. Click on the photo to see more and read about just what it is that you are seeing!

Another well executed example of the ET Westbury "Craftsman Twin", this one built by Allan Jones, pictures by Clive Longstaff, of the Astrophysics and Space Research Group at the University of Birmingham in the UK. I particularly like the neat brazing and plating job on the exhaust stacks.

At the last report, running trials were held up pending delivery of a sufficiently agile spark—and before you say "just fit glowplugs", remember that sparkies generally have a much lower compression ratio than methanol burners, so 'taint that simple...

These pictures were very kindly sent in by Brian Perkins, of Bristol (where else? ), England. Brian's work has appeared here before and is never mundane (check out his Bristol Aquila exhibited at Midlands and details of which appeared in SIC some time ago.

Brian seems to be embarking on a crusade to build miniature, working replicas of all of the engines made by Bristol before the take-over by Rolls Royce. This time his subject is the little known "Hydra", a 16 cylinder, dual bank, poppet-valve, air-cooled radial with an even number of cylinders in each bank (obviously!). But wait, there's more: the cylinders in the two banks were positioned directly in-line rather than staggered as has become normal practice for multi-bank, air-cooled radials. I don't know for sure, but I'd assume that the rockers are actuated by overhead cam shafts, driven by bevel gears and torque tubes from the crankshaft.

The Hydra was installed in the other Hawker Harrier—the between-wars biplane, not the modern V/STOL used by the Royal Navy, US Marines, and Spanish, Italian, Indian and Thai Navies (I believe—please, please let me be right).

Brian has prepared an article for Model Engineer on his latest 18 month odyssey which will appear later this year that should make for very interesting reading. It was the speed reducer gear cluster for this engine that led Brian to uncover an error in the Nexus Workshop series book on gears and gear cutting by Ivan Law. An article describing this appeared in Model Engineering Workshop, number 87 (see Editorial for May, 2003 where I incorrectly call the Hydra a sleeve valve design). Regarding the Hydra, Brian says:

The Hydra was the result of a number of design studies carried out in the early 1930's when they were looking for more power but had not yet succeeded in making the sleeve valve work. They came up with a number of possible configurations and chose to proceed with the Hydra. Only two engines were built, one of which was flown in the Hawker Harrier as shown in Lumsdens book but it apparently suffered from vibration problems believed to have been caused by the lack of a centre main bearing. By this time the sleeve valves had started to work and from there on there were no more poppet valve engines developed


The timing diagram is worth studying. Brian has access to an archive of material through the Bristol Trust and can examine and measure original parts. I'm not sure if one of the two Hydras has survived intact, but at least the distributor has, as Brain says:

...I worked out to be the firing order [but] later found it marked on the distributor which would have saved a lot of effort!!!

So on each complete revolution, two adjacent cylinders of the same bank fire, then alternate cylinders of each bank, swapping to two cylinder of the other bank first on the second revolution of the four-stroke cycle (note the angles on the diagram with the red dot showing the crankpin angle of the firing cylinder). We do end up with a very even order: something goes bang every 45 degrees, and there must be a reason for the "two together" sequence, though I've no idea what it might be. One thing's for sure, if this thing has a ring-cam—which I'm betting it does not—I can't wait to see it!

Some more engines by Les Stone (see his Goose-egg Elf 4 below). Clockwise from top-left, they are a Rogers and Geary "Wasp" (see also R & G Wasp), a Nova I (see also MBI Nova), the Furgerson Falcon and Furgason Condor (see also... I wish! Still, I do have castings under the bench someplace...)

Les used pressure pack black lacquer to achieve the finish on the heads and reports that all engines have been run with no apparent heat problems on the finish. The case finish was applied from a large can of elbow grease.

If your library contains a complete set of SIC (it should!), you can check out more of les's work on the rear covers. See

  • SIC 64, page 32 center of page
  • SIC 65 rear cover lower right hand corner
  • SIC 66 rear cover lower right hand corner
  • SIC 68 rear cover lower right hand corner
  • SIC 69 rear cover lower right hand corner
  • SIC 73 rear cover lower left hand corner