# 1/2 O-200

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

#### Tiger Tim

##### Well-Known Member
One would think it better to hunt-up a Franklin 2AC-120 and be done with it.
I’d like to find one of these for a project I have in mind, but I admit I haven’t looked very hard.

#### challenger_II

##### Well-Known Member
They pop up, from time to time. Just be advised: they shake!

#### pfarber

##### Well-Known Member
BMW bike ect are discarted a they require PSRUs.

How is that a bad thing? I bet that you have no idea of the number of engines that have PSRUs and were considered the greatest engines of their time??

Its hilarious that you would even entertain the amount of work/trouble to cut an engine completely in half, resign the accessories from scratch, modify the oil galleries and crank bearings... but two gears scares the hell out of you???

Lets just say I stopped reading when you made the above statement.

#### Tom DM

##### Well-Known Member
Supporting Member
How is that a bad thing? I bet that you have no idea of the number of engines that have PSRUs and were considered the greatest engines of their time??

Its hilarious that you would even entertain the amount of work/trouble to cut an engine completely in half, resign the accessories from scratch, modify the oil galleries and crank bearings... but two gears scares the hell out of you???

Lets just say I stopped reading when you made the above statement.

Hold yer horses.

Some like PSRU's, reason number 1 it allows the engine to rev higher and thus produce more power. Others do not: the extra parts (far more than 2 gears!), complexity etc. I kinda like KISS (Keep It Simple Stupid), things get complicated fast enough. The second reason why I stay away of PSRU is that they are a trick to convert an engine into something it was not designed for in the first place. In my humble experience such always comes with added little letters at the backside of the invoice.

I do not entertain the thought of cutting an engine in half. Before assuming what scares the hell out of me you might read the OP, read what is there, not read what you think is there.

Compared to any PSRU-engine an 1/2 O200 is "easy" engine: less there is, less to go wrong, weighs less and -most of the time- costs less and lives longer. If the power output is of the required quantity, I would opt for a direct driven prop any day of the week. But you may do as you like: won't bother me the slightest.

#### KeithO

##### Well-Known Member
Sorry Tom, but in fact there are now very few direct drive options left anymore. Those that exist are very expensive and only produced a few hundred per year. The high volume engines like Rotax have a built in gear drive. The high volume auto engine conversions like Viking, have a reduction gearbox. And they are being bought in big numbers now. There are more people entering the auto engine conversion market and I would say output is in fact constrained by the fact that most companies who do produce a good gearbox have the gearbox production integrated into their overall manufacturing plan, meaning there are no gearboxes to be sold as a stand alone product.

Rotax is big enough that they were willing to sell gear boxes or gear box parts, so long as they want to do it. Recently they discontinued the sales of the 2 stroke engines and the C gearbox, so now there is only the "E" gearbox. The 912, 914 and 915 engines have part of the gear case cast into the engine crank case, thus their gearboxes were never designed as stand alone units. Thus if one wanted to use components from those gearboxes on your on application, you would have to have half the gear case made as a casting or machined from solid just to have a complete gear case. + you would likely have th buy the rest of the gearbox as spare parts at a price 3x higher than normal price.

Anyway, the O-100 proposal would have suited some customers for asthetics and sound but certainly wouldnt be the least expensive nor lightest option. Continued supply of the crankcase, crankshaft and camshaft in the future would be rather tenuous because there would be no major financial backing for it. Nor a large installed customer base.

Hold yer horses.

Compared to any PSRU-engine an 1/2 O200 is "easy" engine: less there is, less to go wrong, weighs less and -most of the time- costs less and lives longer. If the power output is of the required quantity, I would opt for a direct driven prop any day of the week. But you may do as you like: won't bother me the slightest.

#### Tom DM

##### Well-Known Member
Supporting Member
Sorry Tom, but in fact there are now very few direct drive options left anymore. Those that exist are very expensive and only produced a few hundred per year. The high volume engines like Rotax have a built in gear drive. The high volume auto engine conversions like Viking, have a reduction gearbox. And they are being bought in big numbers now. There are more people entering the auto engine conversion market and I would say output is in fact constrained by the fact that most companies who do produce a good gearbox have the gearbox production integrated into their overall manufacturing plan, meaning there are no gearboxes to be sold as a stand alone product.

All that is known Keith but does not distract from PSRU to no PSRU.

Then there is the scope of PSRU's itself: it ranges from a belt to a gear-cased unit, from something guaranteed to fail to a unit which seems to get to TBO.

There is UL-motor, Jabiru, there are the old-bangers Lyc and Continental. The mere fact that Rotax hasn't eaten them all and that the kind of UL-Power arrived at the market when Rotax was already very well established- indicates that the PSRU-driven engines are not (yet) the Holy Grail.

Bottom line remains that a direct drive engine is less charged mechanically, less parts, less complex. Quite often a part that is not there, does not fail.

I deliberately leave the Viking, Aeromomentum and other BMW-bike-convertions etc out of the equation, not because they lack merit or potential but because they remain firmly in the "experimental" category. They all claim "many flight hours" and "absence of problems" yet if something fails on them, the end-user is alone. Maybe he is not alone in the US , but in Europe he is. From cases I know: not the nicest of places...

Blue skies

#### Vigilant1

##### Well-Known Member
Supporting Member
Direct drive: Add Limbach as well as Sauer. Both certified by at least some national authorities.

D-Motor, too. Well, I guess. They don't seem interested in selling engines to homebuilders it seems.

Last edited:

#### Tom DM

##### Well-Known Member
Supporting Member
Direct drive: Add Limbach as well as Sauer. Both certified by at least some national authorities.

D-Motor, too. Well, I guess. They don't seem interested in selling engines to homebuilders I guess.

Limbach, Sauer are the "better" VW-convertions. However (in Europe) these engine are mainly on (Fournier)-motorgliders, very little on motorized airplanes.

In Belgium I know but of 3 experimentals (non motorglider) with them and only because they all had severe and catastrophic in flight engine failures. While I suppose the product itselve is not the problem but more the image "it is but a VW". It attracts maintenance / rebuild- conditions not that followed.

This one I know very well, I transported the wreckage back to Grimbergen.

D-motor will happily sell motors but they are a bit scared of the homebuilding scene.

#### Vigilant1

##### Well-Known Member
Supporting Member
D-motor will happily sell motors but they are a bit scared of the homebuilding scene.

They named a US distributor (Dave Hertner) a few years ago, but seem to have closed up that shop.
https://d-motor-usa.com/

#### Tom DM

##### Well-Known Member
Supporting Member
They named a US distributor (Dave Hertner) a few years ago, but seem to have closed up that shop.
https://d-motor-usa.com/

The problem seems always the same: wanting to reap before having sown.

All are looking for a goldmine and while the gold is there, they expect it to be there in bars not in a few grams per metric ton of rock.

#### TiPi

##### Well-Known Member
Supporting Member
I haven't put my 5 cents (to account for inflation) in this thread yet, so here we go:

The O-100 "seems" to an engine that could find a market, as Pete Plumb spent many years of research and R&D on his project.
Unfortunately, the reality is that the 50-60hp segment is very price sensitive (as is the 30-50hp segment).

• Jabiru started with a 1600cm3 54hp engine and went to the 2200 80/85hp within a couple of years, same cost and more power/usefulness.
• HKS had a nice engine with a good reputation but didn't last that long, most likely due to low demand from high price (they were around USD10k)
• Anyone remember the KFM112? Its production stop forced Jabiru into their own engine design & manufacturing.
• There was/is a Rotax 912/2 prototype, using the 912 cylinders & gearbox on a custom-made crankcase.
• Verner produced a few lower power engines, but not for long (smallest one is now the 83hp Starlet 5S).
• Straight 1600cm3 - 1835cm3 VWs are about the only currently commercially available (kit or fully built) engines at resonable prices, at a weight penalty.
• The Aeromarine V-twin is the only newcomer with deliveries yet to start.

So what is causing the demise or production stop of all of these engines? Apart from the R&D driver passing away, it looks like the main driver was lack of sales due to cost or lack of market acceptance in the time required for the business to survive.

In my opinion, the only product that will succeed in this segment is an engine that uses as many mass-produced parts from an accepted, reputable OEM, assembled with the least amount of custom parts into a simple, no-frills engine that can compete with the current 2-stroke engines for cost (say life-cycle cost over 500h).

As the time of air-cooled engines from automotive sources (VW, Corvair, Citroen etc) is over, the only source remaining for now is the industrial engine and maybe some motorcycle components.
Using full-size aircraft engine parts (O-100 and 1/2 Rotax 912), added to a custom-made crankcase, crankshaft, camshaft and all other accessories needed for a functional engine, puts the cost above the 50% mark of the full-size engine. The only viable option would be salvaging a worn engine by modifying it to the desired size, but that might be more for one-offs and not as a business.

For any direct-drive engine with a required 50-60hp, the current crop of industrial engines is too small in size (bore & stroke) to allow for a 2-cylinder. Getting a 3 or 4-cylinder built from industrial engine components requires custom-made crankcase and most other rotating parts.

So that only leaves the smaller, higher-reving type of engines like the Aeromentum V-twin and similar engines based on a mass-produced engine that is suitable for sustained high power levels.

The 20-50hp segment can be covered by air-cooled industrial engines in direct & redrive, as several examples are already showing, as well as the 1/2 VW where the weight can be accommodated.

#### TFF

##### Well-Known Member
Profit for effort is very low in aviation. Even airlines. Once real business people see it’s not a cash cow, investment dries up. If you don’t have an owner willing to babysit every aspect, it’s going to fall apart. It’s not an “easy” investment like other companies. You also have the interesting part where these businesses attract the geeks. These businesses don’t do well as 9-5 worker bee jobs.

Space X vs Blue O vs Boeing…. Space X has a babysitter. Boeing relies on old infrastructure; babysitters grew up and left the neighborhood. Latchkey. Money people are in charge, so they at least don’t have to develop, they can ride a line. Blue while hiring great people to do the jobs, no one is there to stick their neck out except pocket book. Companies that are just bigger than mom and pop company have no chance. Can’t buy your way in to make money.

I saw the prototype of the O-100 at Oshkosh and it was very nice for a first article. It just ran out of time. From the threads there seems to be about ten engines worth of parts.

#### Bill-Higdon

##### Well-Known Member
Limbach, Sauer are the "better" VW-convertions. However (in Europe) these engine are mainly on (Fournier)-motorgliders, very little on motorized airplanes.

In Belgium I know but of 3 experimentals (non motorglider) with them and only because they all had severe and catastrophic in flight engine failures. While I suppose the product itselve is not the problem but more the image "it is but a VW". It attracts maintenance / rebuild- conditions not that followed.

This one I know very well, I transported the wreckage back to Grimbergen.

D-motor will happily sell motors but they are a bit scared of the homebuilding scene.
From the report you referenced "
Contributing safety factor:
Performing non-routine maintenance on critical aircraft components without having extensive
technical experience.
Other safety factor:
The lack of technical documentation and/or guidance from the engine manufacturer to warn the
mechanics about the “valve stem wear phenomenon”, possibly causing an insufficient gap between
the valve rotators and the rocker arms. "

A lot of people in the US use the VW maintenance Manuals for general maintenance & tech help on their basic engines

#### KeithO

For the longest time the HKS engine was sold for a little over $6000. When they raised the price to$10k, I think that was when sales dried up and they finally stopped production. At $10k they were significantly more expensive than competing 50-65 hp engines from Rotax and Hirth. Then not long after HKS pulled the plug, Rotax also pulled the pug on the remaining 2 strokes and the B and C gearboxes that DIYers might use to build their own engine. These moves killed off several airframes that were designed around these engines. I haven't put my 5 cents (to account for inflation) in this thread yet, so here we go: The O-100 "seems" to an engine that could find a market, as Pete Plumb spent many years of research and R&D on his project. Unfortunately, the reality is that the 50-60hp segment is very price sensitive (as is the 30-50hp segment). • HKS had a nice engine with a good reputation but didn't last that long, most likely due to low demand from high price (they were around USD10k) #### Tom DM ##### Well-Known Member Supporting Member From the report you referenced " Contributing safety factor: Performing non-routine maintenance on critical aircraft components without having extensive technical experience. Other safety factor: The lack of technical documentation and/or guidance from the engine manufacturer to warn the mechanics about the “valve stem wear phenomenon”, possibly causing an insufficient gap between the valve rotators and the rocker arms. " A lot of people in the US use the VW maintenance Manuals for general maintenance & tech help on their basic engines And so they should... but this was no "basic" VW engine on which the VW Manuals for general maintenance were applicable. It was a Sauer aircraft engine, based on the VW motor and here the Sauer-procedures had to be applied. I don't know (too lazy to look) the price of a basic VW-engine in the US but am willing to bet it is significantly less that the Sauer-version which retails around 13000-15000 Eur. #### Vigilant1 ##### Well-Known Member Supporting Member I don't know (too lazy to look) the price of a basic VW-engine in the US but am willing to bet it is significantly less that the Sauer-version which retails around 13000-15000 Eur. FWIW, US prices for built and tested aero engines based on VW Type 1. With carburetor, dual ignition, alternator, starter, prop hub, beefed up prop bearing, etc. Revmaster 2331cc:$9,800

Hummel (Casler) 2180cc: $7,225 Some of the larger Sauer engines are based on Type 4 cases. Regardless, all the VWs do require good care and maintenance, including proper valve lash adjustment. If they are incorrectly adjusted (and especially if they are too tight), bad things can happen. This type of maintenance is nothing special for engines of this type and vintage, but it may not be something modern buyers are expecting. Treat them right, respect their limits (don't run them too hot), and they can give long, reliable, cheap flying hours. At approx$110/HP new, they are a pretty good bargain as aviation engines go.

Last edited:

#### Pops

##### Well-Known Member
Supporting Member
I always change oil and check the adjustment of the valve lash at 25 hrs and record the measuments I found to catch any problem. Just about an extra 10 minutes while doing the oil change.
I have somewhere about a million miles driving behind a VW type 1 engine. Oil change and valve lash check at each 3K miles and new plugs and point and condenser at 10K miles. On a 1600cc engine the mileage reduces from 32 mpg to 28 mpg between 10K and 12 k miles.
My job required a lot of driving and for many years drove a VW 1000 to 1200 miles a week . Bought a new 1969 VW Bug and put 78K on it in 18 months. Yes, I got paid mileage, and paid more than it was costing me.

#### Beragoobruce

##### Well-Known Member
I note that of all the engines of 50 - 60hp cited in this thread , nobody has mentioned the excellent MZ202 or its sibling, the MZ201.
The 202 was the standard engine fitted to the Mosquito helicopter for a while, which must attest to its in-field reliability.

I flew behind a MZ202 on my MiniMax for a couple of years with no issues at all. The engine produces 60hp from 625cc displacement via a proper gearbox with centrifugal clutch and good dual ignition. In 2-stroke terms, it is a big, lazy engine, and yet it weighs in the order of 40kg with electric start, exhaust, etc. The 201 gives 40hp at a few kilos less weight, using a belt drive reduction.

A Max builder here in Australia has just taken delivery of an MZ201 from the which now produces the engine, here: http://www.fiate.net/en/mz202.html

He was very pleased with their service: prompt replies to emails, firm price quotes, etc. The engine was well below 8000USD landed in Australia, I'm told.

Bruce

#### DrStoooopid

##### New Member
You mean like this?

Here it is running:

I'm not associated with them, I just know OF it.

Hi All,

Since in some discussions the O-100 of the late P. Plumb appears from time to time, I have a (slightly) theoretical question.

What if from an O-200 or C-90 the complete assembly of the 2 rear cylinders (closest to the firewall on a tractor configuration) were removed?

By complete assembly of the 2 rear cylinders I mean the whole lot: cylinder heads, pistons , connecting rods , sleeves , push tubes, cam followers. This followed by plugging the holes in order to hold the oil inside.
Exhaust and intake would also require some plugging while the missing reciprocating weight of the connecting rods / pistons needs compensation at their former crank positions. Crankshaft remains as is, maybe with only some minor mods towards lubrification for the rear crankshaft bearings. Camshaft no mods.

Normally carb setting and ignition should stays as were, COG will move towards the prop. The stock O-200 weighs about 100 kg, Weight loss estimated at 35 kg. Power and torque will obviously be halved.

The above should turn the O-200 into an O-100 without any casing modification. Am I missing something obvious?

As for why: I collect my C-90 next week (in parts) being given a -reconditioning offer which I am not happy with. Might as well tinker a bit with it. As always: parts that I don't have , are worth fortunes , the parts I do have worthless. If some-one has a decent O-200 or C-90 blocking his doorway, one needed here.

Blue skies

#### KeithO

##### Well-Known Member
No, not like that, the OP is suggesting you take a full O-200 engine and just remove 2 cylinders (maybe the back 2) and close off the crank case, leaving the full crankcase so no new special parts are needed and you can get everything you need from existing O-200 parts stock. Obviously, remove the lifters from the cylinders no longer running. The cam may have to be changed to achieve the proper timing for the 2 remaining cylinders (exactly 1 revolution apart). I have not investigated the standard firing order of the cylinders...

You mean like this?

Here it is running:

I'm not associated with them, I just know OF it.