aerovee vs revmaster

[radfordc]

I think there are reasons Aeroconversions does not offer assembled engines:
Liability. If you offer an engine kit, anything that goes wrong with the engine in flight can be easily attributed to "builder error," whereas if you offer an assembled engine, you take on a lot more liability for what happens to that engine when it's run. Given Monnett's legal history, this might actually be the driving consideration here.

If you had been sued out of existence before (I believe John Monnett has) you would be very careful about liability, too.

[joepowel70]

In the end all the major VW conversion companies make nice engines, and it comes down to which small details you like better and whether you need/want FWF support.

From my limited research, it seems like all major VW conversion companies (Revmaster, Hummel, Great Planes, Limbauch, etc) offer a larger #4 bearing for the prop hub. Aeroconversions is the only company that relies on the stock VW bearing to take all of the load from the prop. I'd think this is more like a large detail. Ignition, intake, exhaust, accessories, etc... I consider small details.

[NWade]

Some things to think about:

1) Which VW conversion engines rely on custom parts that you can only get from 1 manufacturer?
(Think about the long-term sustainability of these companies and parts-supplies)

2) Which VW conversion engines have cases that are beefed up with additional welds and reinforcements? What parts are forged versus billet CNC machined items?

3) Which VW conversion engines have 100% zero-time parts?

There are a lot of detailed differences between these engines. As someone who used to build racecar engines with a few low-budget NASCAR and SCCA teams, I can say that engines are not nearly as simple or as easy to judge as airframes. A reciprocating engine has a lot of moving parts and a lot of wear items. How they're sourced, built, and reinforced matters. Do your homework. Don't believe the marketing hype. And remember that you get what you pay for.

--Noel
P.S. Joe, those "small details" you talk about can still affect the reliability of your engine. Don't neglect them. And don't concentrate too much on that one bearing. Look at the associated loads and the other structures besides the single bearing that help support those loads.

[Mike53]

In doing a quick comparison between Aerovee ,Great plains and Revmaster I came up with these figures-
Great Plains 2276cc achieves less than 80 HP @ 3400 rpm (how much less I haven't determined yet)
Aerovee 2180cc achieves 80 HP @3400 RPM
Revmaster 2331cc achieves 80 HP @ 3000 RPM Revmaster is also rated for 85 HP at 200 RPM more( used for takeoff -not continuous)
I'm not a mechanical engineer,but I would think that over the long hall that continuously running your engine at a lower rpm will significantly lengthen it's TBO?It should be noted that the above 3 RPM's 3400,3400 and 3000 are continuous rpm's
Opinions?

[Andy Walker]

I'm not a mechanical engineer,but I would think that over the long hall that continuously running your engine at a lower rpm will significantly lengthen it's TBO?It should be noted that the above 3 RPM's 3400,3400 and 3000 are continuous rpm's
Opinions?

Yes and no. Lower RPM is better, but the larger size of the Revmaster comes with thinner cylinder walls and a longer stroke, which means a weaker block and more stress on connecting rods and wrist pins. In the end it's probably six of one, half dozen of another.

[Mike53]

I'm not a mechanical engineer,but I would think that over the long haul that continuously running your engine at a lower rpm will significantly lengthen it's TBO?It should be noted that the above 3 RPM's 3400,3400 and 3000 are continuous rpm's
Opinions?

Yes and no. Lower RPM is better, but the larger size of the Revmaster comes with thinner cylinder walls and a longer stroke, which means a weaker block and more stress on connecting rods and wrist pins. In the end it's probably six of one, half dozen of another.

Andy I understand what your saying about having to machine a stock case for clearance to accommodate the longer stroke but it is my understanding that Joe Horvath at Revmaster makes his own cases so I'm not sure if having a longer stroke is going to play out the same way as if you were using a stock vw case?If you design the case for a longer rod I would hope that the thickness of the case would be more than adequate but I don't really know for sure one way or the other.Revmaster engines don't really contain any VW parts which as someone earlier pointed out could be a problem if Revmaster went out of business.

From the EAA Experimenter article at the beginning of this thread submitted by Chris.....'Custom-designed dual-plug heads with proprietary roller rockers, custom-forged connecting rods, and oversized external oil cooling round things out.

[Andy Walker]

Andy I understand what your saying about having to machine a stock case for clearance to accommodate the longer stroke but it is my understanding that Joe Horvath at Revmaster makes his own cases so I'm not sure if having a longer stroke is going to play out the same way as if you were using a stock vw case?

Stroke is the distance the piston has to travel. You can't "cheat" on that...if the stroke is X on two different engines, it really doesn't matter what the case looks like, the distances are the same; the pistons have to move up X and down X on every stroke.

The problem is inertia. If you have a 5oz piston moving a certain distance X, and then increase the stroke to 2X, the piston now has twice the distance accelerating, before it suddenly has to change direction. Since force = mass * velocity^2, you get a lot more force against the piston wrist pin and the rod itself.

Don't get me wrong, there is nothing inherently wrong with "stroker" motors, and as long as all components are up to the task it poses no longevity issues. But there is additional stress, and it should be accounted for when building the engine (I'm sure Revmaster has this covered very well).

[Mike53]

Thanks Andy.We are talking 2mm increase ie; 82mm to 84mm and with a piston velocity 400 rpm slower in continuous operation, based on what you have explained I will assume this is not critical on the Revmaster though the Bore is also 2mm larger which will as you said add a weight factor due to a larger piston.
Fun Stuff :mrgreen:

[rizzz]

The RevMaster engine looks nice, I

[kmacht]

Something to think about, just because the engine mounts are the same on the revmaster/great plains / aerovee, doesn't mean that it will still fit the same engine mount and airframe. Things like the starter, alternator, intake, and exhaust for the aerovee were all designed to fit around a Sonex/Waiex/Xenos mount and cowling. Are you sure that the other companies will fit or are you willing to design a new mount and cowling to make it fit? Will the sonex baffling fit or will you have to design your own? Is the prop hub lenght the same? Lots of variables to think about.

Keith
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