Radial VW?

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Cabover

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A couple of weeks ago I started a thread about water cooled heads. I learned a lot. For an inexpensive engine the VW is attractive. If I were to give one a try I might put on the weld on band and use antifreeze cooling. I think I would also prefer a PSRU off the clutch end.

I stumbled upon a Yahoo video. It is of a Radial engine using a lot of VW parts. The heads were cut down and turned round. My impression was that the cooling was too greatly reduced. I drew the conclusion that the engine was put together as either a personnel challenge just to see if it could be done, or it was an intermediate stage of development.

After looking at Rotec I came to the conclusion that it is a fine engine. Expensive to buy, expensive to overhaul.

So, here is the question. Could a radial be developed using VW and other common automotive parts, especially for the overhaul stuff?

The idea would be to make as few hard parts, cases cams etc. as possible. For the parts that get replaced at overhaul shell bearings, bushings seals gaskets, oil pumps etc. These should be VW or other common and inexpensive parts.

Radials work in odd numbered cylinders. 5,7,9 are practical. 5 is not sufficiently bigger than a flat 4. 7 is close to double the size of 4 as is 9. The 7 should produce about 125HP and the 9 about 150. The front case would be the ideal place for a gear reduction. I have assumed no boost in the intake pressure.

I’d like to keep the initial cost down. Less than a Rotec but a lot more than a VW flat 4. The advantage would be at overhaul.

So, comments? Was that fellow that made the Youtube actually on to something?
 
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JamesG

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So, comments? Was that fellow that made the Youtube actually on to something?
Gets done periodically with Vee Dubs, Beemer airheads, or any other individual aircooled cylinder motor, even Harleys. Google "radial" + whatever to get links and videos. Yes, most of them are done as engineering and fabrication exercises.

I'm waiting for someone to take a crack at a Honda Goldwing/valkyrie based 2 or 3 bank cylinder radial engine!
 

fly2kads

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The HCI radial was made with VW pistons and cylinders, and was available in 5- and 7-cylinder versions. I think plans might still be available, but that you'd have to source or make your own parts.
 

akwrencher

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Supposedly you can still order plans,however I did quite a bit of searching last winter and was not able to get a current address for the guy that has them. If anyone is successful in contacting him, I would be interested in ordering a set as well.
 

Vigilant1

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The idea has appeal. Because it would be designed for airplane use, the case and front bearing could be made strong enough to take prop loads, and likewise with the crank (desifgned to take a prop hub). Heck, it could be set up for a CS prop if desired. Plus, engine mounting points optimized for aircraft use, a case that supports the piston skirts well so that a long stroke is less problematic, etc. Good head cooling (put all the exhaust valves right up front, no "rear" cylinder) . . .

7 jugs x 20 HP each = 140 at SL, and still have 100HP at 8000' MSL.
 
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johnnyd

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There is a Yahoo group for the HCI radial engine. Look for HCIRadialbuilder. You should find all the info you need there.
Keep in mind that the HCI radial is a direct drive engine. The Rotec & others are "geared" via a planetary type drive mechanism.

John
 

RJW

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The idea would be to make as few hard parts, cases cams etc. as possible. For the parts that get replaced at overhaul shell bearings, bushings seals gaskets, oil pumps etc. These should be VW or other common and inexpensive parts.
VW Radial 10.jpg


This would need crankcase, rods, cam drives, as well as many smaller parts. The crank is the center two throws from an SBC. The motor would not have even firing (36/108 degrees, I think) and would inherit all the bad features of VW heads. But it would probably be very durable at 100HP without a gearbox. Add gears and something like 120HP could be had.

How are your engineering skills? Do you have any machine tools? I live in central Wisconsin. Do you want to build this?

Rob
 

Vigilant1

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Rob,
Thanks for that drawing. What would be the limitation on the HP of a design like this? At the 100 HP you've cited, that would be just 10 HP per cylinder, so this design would be fairly heavy for the HP produced (but head cooling shouldn't be a problem).

Mark
 

Autodidact

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Make it a 6 bank and you've got a 400 ci even fire 12 cylinder with a very stiff crankshaft...

You could do the same thing with type 4 heads and BBC crank center - 600 ci. Somebody needs to do this!
 

RJW

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What would be the limitation on the HP of a design like this?
This arrangement would have the same cooling limitations/exhaust valve wear of boxer VW motors. While some run their VWs to 20HP per cylinder or more, it is my opinion that no more than 15HP per cylinder should be asked of these engines if good durability is desired. Yes, the 10HP per cylinder figure is probably too low. But it’s safer to err on the conservative side IMO.

And no idea really of power/weight. It’s just a paper motor—without a lot of paper.:)

Rob
 

RJW

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Make it a 6 bank and you've got a 400 ci even fire 12 cylinder with a very stiff crankshaft...

You could do the same thing with type 4 heads and BBC crank center - 600 ci. Somebody needs to do this!
Yeah, a twelve would have even firing but it starts getting kind of huge and cam placement gets pretty hard. It could be done though.

I like an X8. It would be simplest, I think, and would have even firing.

What I see as the biggest problem is that the use of a standard master/slave rod configuration makes these motors pretty big for the power they would make. If you made it a two-row six you could use slipper rods like the Sadler radial and end up with a very compact motor. But it would have uneven firing (unlike the Sadler). I don’t think it’s practical to use slippers on motors with more than three cylinders per bank and a one-piece crank. Maybe something like the Nordberg setup that jac posted would make a compact radial?

Does the type 4 bore spacing work with a BBC crank?

Rob
 

RJW

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According to this list...it may just be possible.
That’s plenty close enough to make it work. It’s about the same with the SBC and type 1 IIRC.

A case for an X8 would be easiest to make since it could be split simply and would need only two cams (though they would need to be custom ground). Similar for the Hex12 but three cams would be needed and they would be difficult to place. A 10-cylinder crankcase would be difficult to make/assemble and would need 5 cams (unless there is a clever way to bump the valves similar to the Sadler that I’m not seeing).

Maybe somebody should pick one of these configurations and start carving a crankcase pattern.;)

Finished motors would be much larger than depicted in the attachments mainly due to master/slave rods/acceptable rod angles.

Rob
X8.jpgHex12.jpg
 

Pops

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VW heads do not cool properly unless the air goes down through the head, not from exhaust end to exhaust end, so the airflow will be coming from the front then will have to bend 90 degs, through the head and another 90 degs to the rear.
Dan
 

Vigilant1

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VW heads do not cool properly unless the air goes down through the head, not from exhaust end to exhaust end, so the airflow will be coming from the front then will have to bend 90 degs, through the head and another 90 degs to the rear.
Dan
Yep. The double-row arrangements wouldn't be worse than the standard flat four in this respect, but just from a cooling perspective it would be optimum to get all the exhausts facing forward.
I think we might also find that, with the known VW head cooling limitation addressed in this way, and the shorter, stronger crank that a custom built radial would allow, that higher HP per cyl might be reasonably and reliably achieved (through higher CR, for those willing to burn 100LL, etc).
 
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