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Simple, proven, off-the-shelf industrial V-twin?

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Vigilant1

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This thing looks like a pretty heavy lump. I haven't yet found a weight for it.
Uggh, you are right about that. Amazon says they weigh about 19 lbs. That might include a very heavy box?? Hey, it's an option! This starter/generator + the pulley/prop hub is probably still a little lighter than the flywheel + starter + prop hub it would replace. More importantly, it gets rid of the weight on the flywheel end of that crankshaft.
 
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Vigilant1

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Are there already holes or something in the flywheel to bolt the extension to or is some precision machining required?
I'm not sure of the details of how the prop extension is attached to the flywheel.
There's a picture in this post in TiPi's engine build thread showing the front of the MiniSport SE33 engine (based on the B&S 49 series) showing their prop extension/flange mounted (silver) to the modified flywheel (grey).

Here's a picture of the outside face of the stock flywheel for the B&S 49 series engine. 1600913729276.png

It looks to me like they drilled new holes in the flywheel to mount the prop extension.
 

TiPi

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Correct, the vertical engines only have holes for the puller (2x inner) and the fan (4x outer). I think Spacek simply drilled & tapped another 2 holes on the puller hole PCD.
Many of the horizontal engines have 3 or 4 holes in that same area for a flywheel end PTO. They are ususally rated at reduced power (~50%).
 

Vigilant1

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Correct, the vertical engines only have holes for the puller (2x inner) and the fan (4x outer). I think Spacek simply drilled & tapped another 2 holes on the puller hole PCD.
Thanks. So, assuming the two puller holes are properly centered they would serve as a guide to aligning the extension/hub and for drilling/tapping the two additional holes.
It seems these tapped holes in the cast steel (iron?) flywheel have proven sufficient to the task.
The sourcing and price of the prop hub/extension is something I haven't looked into. I don't know if Spacek s.r.o and their dealers sell them individually or if a builder would need to look elsewhere.
 

pictsidhe

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I've been looking at making a prop adaptor so I can test an engine without a redrive. It will not be hard to make.

Take a piece of 4130 bar and weld a prop flange on the end. True it up in a lathe and bore a 7/8 hole. Broach the keyway. Machine the hole tapered to match the crank. Drill the prop flange holes. Now make a mount to take the ignition magnet, easiest to make something that bolts/rivets to that nice flange that was just made. It could also be welded to the central tube. If you are not man enough to hand prop, same for the ring gear. For testing, I am not going to bother with a starter. A machine shop shouldn't kill you to make one of these. A buddy may only cost beer or a reciprocal favour.

I am going to use the Rotax C box style flange as a standard.
 

Vigilant1

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I've been looking at making a prop adaptor so I can test an engine without a redrive. It will not be hard to make.
If somebody wanted the whole enchilada, I suppose another pulley sheave could be mounted at the base for the golf cart starter/generator belt (if that thing would work in this application). Cutting a pulley groove in the bar would be easy, but would weaken it a lot.

Making the "Pictsidhe Adapter" of various flavors could be a nice side business. Just saying . .
 
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JohnB

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Just a data point, for the last 6 yrs I've been sitting on a 36 hp Vanguard mounted to a 6' deck Scag zero turn. I mow the runways at our airpark 26 acres. I run at rated rpm, no guess abt power used but its on the gov ALL the time . Think I'll plug in a MP guage to see actual. Flawless until abt 400 hrs when an exhaust valve stuck, followed about 100 hrs later by the other side sticking, switched to Briggs oil developed for this issue (as well as others) and no more sticking. Last week I thought I had another valve issue but a rocker arm broke 3 forced landings at abt 30% power in 800 hrs. Depending on airframe you MIGHT maintain altitude on one cyl. O&F gets changed every 30-50 hrs.
John B
 

BBerson

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Could inspect or replace the heads at 300 hrs. That's about 10 years, on average. My Briggs 24hp mower has over 1300 hours.
Try diesel oil.
And yes, always fly airframes that do nice out landings.
 
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Victor Bravo

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Take two identical V-twins and mount them mirror image (flipped vertically) on the same mounting beam or plate. Put a gear on each PTO shaft, and in between the two PTO shafts put an idler gear that has a prop flange on it. This combines a reduction drive with larger displacement, creating a small 4 cylinder radial with a planetary redrive. The big complexity is re-routing or modifying the oil system, but similar work is already being done to convert the vertical shaft engines.

V-twin experts, how feasible or un-feasible is this, in return for whatever you would get in return?
 

Vigilant1

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Take two identical V-twins and mount them mirror image (flipped vertically) on the same mounting beam or plate. Put a gear on each PTO shaft, and in between the two PTO shafts put an idler gear that has a prop flange on it.

V-twin experts, how feasible or un-feasible is this, in return for whatever you would get in return?
I'm no expert, but I'll play:
1601008613410.png
Packaging: If we look at the B&S 49 series (810cc), each engine measures about 16" from the bottom of the crankcase to the top of the heads. So the width of the two engines would be 32" plus any additional room needed for the prop shaft and gear. Not as narrow as a true radial would be, but probably not a deal breaker.
The 18.61" size going the other way (across the heads) would be relatively svelte compared to a radial engine of comparable displacement.

Weight: Maybe a problem. Ready for flight, these engines weigh about 77 lbs (with the flywheel) so 154 lbs. That's a lot of weight for a 60 lb engine. If we eliminate the individual flywheels and use the prop/other engine to provide the rotational inertial to keep the engines running smoothly, then the fit of the gears will need to be >very< close.

Complexity: In addition to the TV/etc issues of the gearset, would we use a single ignition system to assure the engines run at the same RPM? Over-running clutches to allow one engine to turn the prop (weakly) if one engine fails? Will the FAA call this a twin with all that entails?

But, this whole idea significantly departs from Matt's objective for this thread, as given by the title.
 

pictsidhe

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Take two identical V-twins and mount them mirror image (flipped vertically) on the same mounting beam or plate. Put a gear on each PTO shaft, and in between the two PTO shafts put an idler gear that has a prop flange on it. This combines a reduction drive with larger displacement, creating a small 4 cylinder radial with a planetary redrive. The big complexity is re-routing or modifying the oil system, but similar work is already being done to convert the vertical shaft engines.

V-twin experts, how feasible or un-feasible is this, in return for whatever you would get in return?
Thanks for the idea, Rube, but I'm not touching that one with a 40' pole.

Much easier to just build a real radial with Honda jugs.
 

rv7charlie

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Take two identical V-twins and mount them mirror image (flipped vertically) on the same mounting beam or plate. Put a gear on each PTO shaft, and in between the two PTO shafts put an idler gear that has a prop flange on it. This combines a reduction drive with larger displacement, creating a small 4 cylinder radial with a planetary redrive. The big complexity is re-routing or modifying the oil system, but similar work is already being done to convert the vertical shaft engines.

V-twin experts, how feasible or un-feasible is this, in return for whatever you would get in return?
Would kinda define 'odd-fire'?
 

Tiger Tim

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Elsewhere in this forum I posted a video of a Heath Parasol flying on a pretty off-the-shelf Lifan V-twin putting out 26hp at 3600rpm. I think these little industrial engines are here and ready to go, they just need someone with the brains and guts to prove it.
 

Protech Racing

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Thats on my business plan. I'm building the test craft with a baseline Hirth 30HP and hope to swap it for the Twin or BA single .Well see.
 
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