### Help Support Homebuilt Aircraft & Kit Plane Forum:

#### PMD

##### Well-Known Member
From the Frankenengine thread, the mention of the hexadyne really got my attention. Well, not immediately (since it is SI instead of CI) but a 60HP replacement for a half-VW at the same weight that does NOT involve Chinese industrial clones? Yeah, got my attention when I thought about it. So, would like a thread just for this "investigation".

First of all: who remembers anything about the engine itself?

How about the builder Hexatron Engineering and owner Cy Williams (understand now deceased)?

My understanding is that the engine was originally designed for an unmanned drone application.

What does the accumulated wisdom of HBA think the right price is, was and should be?

I would have KILLED for such an engine when I was building airboats (VERY light weight commercial airboats powered by mostly 503 Rotax). Sadly, this thing came over 10 years after I built my last boat.

#### crusty old aviator

##### Well-Known Member
HBA Supporter
I have a Hexadyne engine off an airboat, sitting in my hangar, complete with mount, exhaust ECU, and wiring harness.
It's pretty tragic, the story of Cy and his wee engine. Cy had a very successful machine shop, that was in big demand, and the Hexadyne was his dream that he gambled everything on and lost: not because he was a con man, but because he sent out all the crankshafts to a nitriding house that hired idiots, or at least one idiot, who nitrided not just the bearing journals, but the whole crankshaft! Cy tried, successfully, to grind the nitriding off a few of the cranks, except in the journals, to restore the original ductility of the forgings, but soon realized it required way too much expensive labor, ran out of time with customer orders going unfulfilled, went bankrupt, and had all his machine tools, etc. auctioned off. He destroyed all documentation related to the Hexadyne, as he was so distraught by the horrible turn of events.

##### Well-Known Member
HBA Supporter
I remember seeing the Hexadyne at AirVenture in 2000, and coming away not very impressed with the quality of the castings. They clearly hadn't figured out how to get the metal to flow properly to form the cooling fins; there were holes and irregular edges in a number of spots. I don't think it was anything that would have affected the operation of the motor, but it wasn't very confidence inspiring.

#### mm4440

##### Well-Known Member
Originally designed by Weslake in England. Three throw crank so cylinders are inline and very good balance.

#### PMD

##### Well-Known Member
Best I can find so far is that Cy Williams had some early development issues (2001-1006) but was still in limited production to 2015 or so. He was selling them for something like $8k each - so probably a$12k engine in today's world?

#### jedi

##### Well-Known Member
I followed the engine for many years while nothing seamed to be happening. I had never heard the nitriding story so do not know if that came later or what any connection would have been. I must assume that it came after I lost interest while waiting for production to begin.

I consider myself somewhat of an "engine guy" but never owned one and can't say if I have ever flown behind one but I was involved with a fair amount of engine running and trouble shooting and have seen it fly. I visited Si in Salt Lake City and worked briefly with a few owners on their applications.

I am quite impressed with the design and think it is a very good concept with a quality background. Si acquired the rights in a reasonable deal but his main business was not engine manufacture. He built several (perhaps a dozen) non production engines for development and eventual sale. The plan was to use those engines to get an airframe manufacturer to adopt the engine so that high volume production could begin. I did not think that ever happened but perhaps that is when the 100 cranks were ordered.

That part of the story sounds very similar to where the O-100 is headed. Sorry for the off topic comment.

Among other things Si used a simplified automotive electronic ignition on the pre-production engines. That ignition system was the cause of many customer problems. It was also a dry sump engine that required the oil resivor to be fitted as part of the specific application. I do not recall what the fuel system was.

The problem I saw was Si sold a few of the (expensive) pre-production engines to amateur builders (at cost or there about) expecting them to solve the instillation issues. He did not supply the necessary support and help needed to do a quality instillation. This is where I wanted to help but that never happened. Several builders gave up and used other engines tarnishing Si's reputation.

One of the primary issues was the electronic ignition. The simplified version disabled much of the automotive emission control functions and retained the basic (perhaps too basic) requirements.

Si would put the engine on the test stand in Salt Lake and program the ignition in his application and environment. He would then send the engine to the amateur builder at Sun n Fun in Florida where the builder would install the engine a day or two before the show.

When the engine was hard starting or running poorly Si's answer was it ran fine when I sent it. You fix it. There was no trouble shooting or ability to reprogram the ignition or fuel control unit to suit the application and little time to solve routine application issues. It ran like a military operation, AFU.

As far as I knew, because of issues like this, he never got the necessary attention of major kit manufactures that was needed to set up for volume production.

I would say there appears to be a "golden opportunity" to purchase the Hexadyne manufacturing rights for anyone wanting to make a small fortune in aviation.

Last edited:

#### rv6ejguy

##### Well-Known Member
HBA Supporter
We were in talks with Hexadyne many years back to supply them with EFI/EI and if I recall, supplied one system for test purposes. The project faded out and I didn't know the reasons why at the time. Like many new engine projects that we've been consulted on, this one went the same way and faded into oblivion. Most are under- financed with a poor business plan in place, some are technically unfeasible and most underestimate the scope and difficulty in getting an engine into production. This leads to delays and burning through cash at an unsustainable rate.

I've seen some truly ridiculous designs come across my desk though the Hexadyne had some great ideas and could have worked well IMO.

#### PMD

##### Well-Known Member
I followed the engine for many years while nothing seamed to be happening. I had never heard the nitriding story so do not know if that came later or what any connection would have been. I must assume that it came after I lost interest while waiting for production to begin.

That part of the story sounds very similar to where the O-100 is headed. Sorry for the off topic comment.
Thanks for that account.

Of course, not thread drift at all. The overall question is if it fits into the marketplace now served by HKS, some BMW conversions, and ???? The O-100 would be among that group - all priced somewhere in that 12/14k range for 60ish HP - getting close to 912 prices. There seems to be another crowd starting with 1/2 VW at half this price range and extending down into the converted Chinese industrial engines - but these all top out at 45 HP at the very most.

#### challenger_II

This thread should be required reading for all those folks that want a 100hp engine that weighs 100lbs, and cost $100. #### Gregory Perkins ##### Well-Known Member There have been a lot of great designs that I wish could have made it but the market has always been just too small. remember this one ? Motavia ( using Ford auto motor components ) #### Attachments • 81.3 KB Views: 21 #### crusty old aviator ##### Well-Known Member HBA Supporter I bought my engine from a SLC airboat/hovercraft manufacturer that paid$8800 for it. Si set up the reduction unit and ECI for running at 2700 rpm for them. They were also supplied with a spare crankshaft, different ratio reduction gearing, and other spare parts. The company decided not to continue with developing their Hexadyne installation because of the crankshaft nitriding woes. They later tried to get manuals for the engine through Si’s general manager, and he told them that Si was so crestfallen, he had destroyed all the documentation and tooling for it, so there were no manuals and Si wouldn’t even talk about the engine anymore...so she‘s an orphan with no tooling, etc. My engine is finished nicely. The castings look good, other than the orange paint. I suppose she could be reverse engineered and produced, with an SDS EFI, etc., as my engine is injected, with an inline electric fuel pump.
I did open up the ECU, and looked over the PC card for the name of its manufacturer, but there was none.

#### mm4440

##### Well-Known Member
I was clearing out stuff from old Airventures and look what surfaced.

#### Attachments

• 11.7 MB Views: 46

#### rv6ejguy

##### Well-Known Member
HBA Supporter
Bizarre rod arrangement...

#### PMD

##### Well-Known Member
Bizarre rod arrangement...
I think it is no co-incidence that the designer of the P50 also works with opposed piston engines. This was a common crank layout in them going back almost a century. One piston would be on the center throw and the other would have linkage going from journals on either side to a yoke that ran the opposing piston. Obviously, low speed engines, but decent balance.

#### PMD

##### Well-Known Member
I was clearing out stuff from old Airventures and look what surfaced.
Awesome. From what I have found so far, it appears that Cy Williams continued to de-bug and develop this engine from the time of your brochure (2000) until 2015 or so. The crankshaft problems were another story. The original design called for an exotic Swedish steel (Orvar) and Cy had tried what was supposed to be a US equivalent, but that failed. Haven't found out yet how he dealt with that one. The tooling was said to be in a warehouse as of a few years ago, but so far I can't seem to find any leads on that.

Anyone know who his DC9/10/MD80 crew seat customers were?

#### Gregory Perkins

##### Well-Known Member
Pics and original EMDAIR-WESLAKE info

#### Attachments

• 76.2 KB Views: 19
• 83.4 KB Views: 20
• 64 KB Views: 18

#### jedi

##### Well-Known Member
..........

Anyone know who his DC9/10/MD80 crew seat customers were?
I expect it was MD. MD may have nay have had multiple suppliers.

#### jedi

##### Well-Known Member
85 - 80 - 60 hp at 3,200 - 3,000 - and 2,500 rpm and advertised as 60 hp. Either lots of possibilities or a reason to run the derated power setting.

It would be difficult to get this full power range without a variable pitch prop.

For what it is worth the engine appeared to run fine in the Ridge Runner but then Stace had his own set of problems with other issues.

#### PMD

##### Well-Known Member
Pics and original EMDAIR-WESLAKE info
Now you've done it! Curiosity means I need to find out what became of the Emdair project(s). I vaguely remember these engines from my airboat days, but the attraction of the weight and gearbox of Rotax was irresistible. I used to build direct drive VWs - that took a LOT of time and money (nearly $3k engine 40 years ago) but the little 503 allowed me to build 400 lb. harvesters (wild rice in natural state of remote lakes) with an engine that cost less than$800 and I just had to take it out of the box and bolt it on.

From what I can see, the big issue with a genuine aviation 50HPish engine is that the market who will pay $12-14k for one is extremely small. Another$4k puts one into the 100HP, 2 place arena. I can easily understand the appeal of a \$6k 1/2VW or total cost after conversion of a Kohler V twin lawn mower (although the latter is more like 35 HP at best) but these are really not aircraft engines.

#### crusty old aviator

##### Well-Known Member
HBA Supporter
The 4AO84 gen set engine gives 45HP @ 3600 rpm, direct drive, and powers many airboats.