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SPG redrives from Air Trikes Enterprises Canada ?

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slociviccoupe

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How are people getging over the weight off to ond side when laying an inline 4 honda engine on its side. This is only reason i went subaru over a honda is honda wouldnt fit under cowling standing upright and leaned over is a lot of weight to the right .
 

ToddK

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For example BMW R or Subaru EA EJ with SPG gearboxes are used a lot for tractors. Honda, Suzuki, Corvair... I agree with cluttonfred For example this is a picture of Corvair installed with 1.8 ratio SPG engine.
I have communicated with the gentleman running the corvair on the rw20. He was not happy with the direct drive corvair as he converted it. He said with gearbox (2.03 to 1 SPG2) and a 73” prop it’s like a different airplane. Jumps of the ground like a helicopter. Faster then he was ready for, It climbed so steep and fast it made him uncomfortable so he backed off the ignition advance. I would not be surprised if it turned out that the draggy slow airplanes running corvairs are leaving a lot of power on the table by running the smaller direct drive prop.
 

rv7charlie

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Not surprising at all. The engine can make more HP, and do it at lower BMEP, which can actually lower stresses on the engine in the bargain. Same effect with VW engines. There's a Kolb that flew with a DD VW and the owner said it was a dog. Then he installed a redrive and turned it into a useful a/c. I remember watching the little VW reduction drive 2 seat open cockpit Valley Engineering a/c (a few closeup pics here) at OSH back in the '90s. It outperformed everything else on the ultralite strip except the helicopters.
 

rv7charlie

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How are people getging over the weight off to ond side when laying an inline 4 honda engine on its side. This is only reason i went subaru over a honda is honda wouldnt fit under cowling standing upright and leaned over is a lot of weight to the right .
Most of the 'canted' inline engines cant the redrive opposite from the engine lean, so that the prop centerline is 'above' the line of the cylinders. That moves some of the engine mass to the other side of the prop.
 

Vigilant1

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Not surprising at all. The engine can make more HP, and do it at lower BMEP, which can actually lower stresses on the engine in the bargain. Same effect with VW engines. There's a Kolb that flew with a DD VW and the owner said it was a dog. Then he installed a redrive and turned it into a useful a/c. I remember watching the little VW reduction drive 2 seat open cockpit Valley Engineering a/c (a few closeup pics here) at OSH back in the '90s. It outperformed everything else on the ultralite strip except the helicopters.
This can work well, the slower prop RPM and longer prop also improving prop efficiency esp at low speeds.
What doesn't work well, based on hard-won experience, is fitting a PSRU to an air cooled engine and a draggy airframe, producing more HP than it was making with a direct drive prop, and expecting the CHTs to stay reasonable and the engine to be happy. Wayne Clagg made a lot of very well thought-out attempts to get a VW with a redrive to work on his Zenith 701, and eventually had to abandon the effort.
 

ToddK

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My own bird if getting 100hp direct drive corvair. It seems to work pretty good on the 750 so I bet it works great on the Cub Major.
 

rv7charlie

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RE: Z701,
Makes perfect sense, if you're asking for more than designed power requirements for the airframe. But at the same HP (assuming proper attention to cooling ducting), it should take no more cooling air with a redrive than without. With the bonus of better climb from the same HP, due to increased low speed prop efficiency.

If you're actually using more power, cooling would obviously need to be increased, and there's a limit to how much heat can be rejected by VW heads. Did he increase air inlet/exit sizes? Install any kind of diffuser and/or flow directors to help with what little pressure recovery would be available, and get air flowing efficiently through the cylinders? Even supposed 'cookie cutter' airframe/engine combinations like the RVs have seen radical improvements in cooling (and drag reduction) with cooling mods; some of them simple and some, not so much.
 

Vigilant1

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If you're actually using more power, cooling would obviously need to be increased, and there's a limit to how much heat can be rejected by VW heads. Did he increase air inlet/exit sizes? Install any kind of diffuser and/or flow directors to help with what little pressure recovery would be available, and get air flowing efficiently through the cylinders?
Wayne Clagg tried everything reasonable to let that engine make about 100hp at his airspeed. He attached "fat fins", adjusted the baffling, etc. He has (had?) a good blog that discussed this, and we've discussed it a bit here. Pops knows him well. Wayne took a very systematic approach and couldn't make it work. He likes the Rotax 912 he put in a lot.
With the VW Type 1, 75 continuous HP is about the limit. Even if it could be made to cool above that, the bearing saddles in the case and the magnesium case itself are other limiting factors. It is a very good, economical, and reliable aero engine up to that point, and it should be appreciated for that, and its limits respected. IMO
Another (perhaps too obvious) thing on airflow and cooling: to cool heads, air has to be in contact with the metal. In practice, this means that where cooling is critical, air must be kept close to the fins and moving quickly. The gaps are small, so this requires pressure. Well designed inlets and outlets help, but in the end many installations require a certain amount of dynamic pressure to achieve the required flow through the plenum and baffling. The available dynamic pressure is four times greater at, say, 120kts than if we are at 60 kts. That impacts available cooling a lot.
 
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rotax618

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I canted the Suzuki over at 70deg, as you can see there is very little asymmetry in weight, the crank side of the engine is the heaviest part.214D3914-3C59-404A-B8EA-70C8CC0BC154.jpegF0CB7861-74F1-4504-822D-20BC857C9B72.jpeg
 

rv7charlie

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I kinda feel like someone asked me if I can walk 10 miles, and after I say yes, they say, 'Oh, by the way, it'll be in Antarctica, in winter, at night, barefoot, in a T shirt & shorts.

No argument about less dynamic pressure at lower speeds. But asking for 100 HP in an a/c (where most of that HP is needed continuously) from an engine designed for 40 HP (typically producing less than 25 HP) in a car, with fan forced cooling, isn't about the redrive. It's about wildly unreasonable expectations. I wouldn't expect it to adequately cool, even if it were installed in a Quickie 2, or some other relatively fast a/c, at that HP. Just too many BTUs for the fin area of the cylinders/heads to shed fast enough.

Expecting more HP, continuously, than the 'stock' HP of a car engine, is the 1st sign of a conversion attempt doomed to failure.
 

Vigilant1

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... it isn't about the redrive. It's about wildly unreasonable expectations.
We agree. It is about asking too much from the engine, and, in the case of VWs, expecting that an engine run through a PSRU can produce more continuous HP than a direct drive. It cannot, because our limitiom isn't volumetrics, it is heat.

That's why this caught my attention:

The engine can make more HP, and do it at lower BMEP, which can actually lower stresses on the engine in the bargain. Same effect with VW engines.
A lot of dreamers have ruined good VW engines and their airplanes trying to use a PSRU to get more HP. They might get more thrust (useful in itself), but the engine won't make more continuous HP reliably. Things could be very different with a liquid cooled engine with excess cooling capacity.
Expecting more HP, continuously, than the 'stock' HP of a car engine, is the 1st sign of a conversion attempt doomed to failure.
That is a logical starting point if there's no history of other successful installations in aircraft. Once there's some experience, obviously, there's more to base things on.

Anyway, enough of that.
 
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ToddK

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The 1200r is a fairly well proven conversion, but not seen widely here in the states. Almost bought a parts bike to get the engine.
 
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