Single-seat ultralight puddlejumper: the "Carbonmax"

Help Support HomeBuiltAirplanes.com:

Hephaestus

Well-Known Member
Gotta keep scale in mind too - those cylinders would be largely hidden behind an 8" spinner, only minor bulges required to hide. I did a couple sketches way back when in the Briggs conversions thread.

Advantage of flipping is minimal IMHO.

Vigilant1

Well-Known Member
There exists an interesting and unique opportunity for a prop extension, because the V-twins have a dozen or so threaded holes built into the front side (PTO) of the engine, for mounting the engine to various equipment. Those holes appear to be valid hard points with good structure around them.

So you could make a little welded tube or sheet metal pyramid that mounts to the engine itself, and supports a thrust/radial bearing a foot in front of the engine, and relieves the crankshaft of all of the propeller flight loads. This would be a bolt-on item. No need for a reduction unless you're fixated on low speed thrust.
As usual, the details make the situation more complex than it might appear at first. The PTO bearing is bigger than the flywheel side bearing, but on most of these engines that flywheel also serves as the alternator stator, the magneto magnet mount, and the mount for the starter ring gear. Mounting the prop extension directly to that flywheel keeps all the significant inertia on one end of the crank, which is critical. Most important--planes are flying with this arrangement successfully: cranks aren't breaking, bearings aren't failing.
Hanging the prop on the PTO end does have some advantages, and there are theoretical advantages to an add-on external bearing. And, there are challenges (complexity as noted above, also the configuration of the crank nose on most versions of the PTO end of the crank--a deep shear key channel and a central tapped hole-- not as beefy as the tapered end on the flywheel side). Using the PTO end could end up being optimal, but it is not the simplest or cheapest approach, and the simplest approach hasn't proven to be operationally deficient.

Last edited:

plncraze

Well-Known Member
HBA Supporter
I mentioned the Maximizer because it is an example of a simple approach to adding a reduction drive. One shaft with eccentric 's for tightening.

BoKu

Pundit
HBA Supporter
It appears that the Briggs 810cc is only available as a vertical shaft engine. There is no horizontal shaft equivalent.

Vigilant1

Well-Known Member
It appears that the Briggs 810cc is only available as a vertical shaft engine. There is no horizontal shaft equivalent.
Yes. But turning it to a horizontal shaft is a road well travelled. Handling the oil is not complex. The 810 also occupies a unique spot with regard to hp/lb and also hp/$in this hp range (for industrial engines). If you can get by with 22hp, then there are horiz direct drive alternatives. The horiz engines giving 25+ hp are much heavier and more expensive "big blocks". Jay Kempf Curmudgeon in Training (CIT) Lifetime Supporter They do? How so? Lots of folks own and/or fly airplanes that really know nothing about riveted joints. And a bunch of folks now are building airplanes with pulled rivets instead of bucked rivets... I gotta disagree with the premise, although I agree that broader knowledge is not a bad thing... Billski Was supposed to be one of those grumpy old man jokes like real men pull the engine first or we should all have to learn to use slide rules... Topaz Super Moderator Staff member Log Member It appears that the Briggs 810cc is only available as a vertical shaft engine. There is no horizontal shaft equivalent. Yes, welcome to the wonderful, wacky world of industrial engine conversions. The threads we have here range from dirt-simple conversion of things like the Harbor Freight Predator 670cc horizontal-shaft engine, on up to conversions of the Briggs 810cc, converted to run horizontal-shaft, and on up through EFI/supercharged beasts putting out over double the original power rating. I'm strongly holding to a Predator 670cc engine for my one-off but, if you're considering series/kit production Bob, I think I'd go for something a little more mainstream, like a Hummel/Casler 1/2 VW. Yeah, the jugs stick out the sides of the nose, but you (or your customers) can buy complete, ready-to-run engines and not have to mess around with converting their own. The alternative is the Valley Engineering "Big Twin" V-twin conversion - same deal, you get complete ready-to-run engines. I don't think "generic" V-twin conversions have become "settled" enough for prime time, in terms of a design that will see a series run, even as a kit. For a one-off? Absolutely a viable choice. Hephaestus Well-Known Member I don't think "generic" V-twin conversions have become "settled" enough for prime time, in terms of a design that will see a series run, even as a kit. For a one-off? Absolutely a viable choice Should we ask Ron how many Q1 quickies are still on the register? If the design is sounds even if engines become unobtainable - the builders will sort it out Topaz Super Moderator Staff member Log Member Should we ask Ron how many Q1 quickies are still on the register? If the design is sounds even if engines become unobtainable - the builders will sort it out Q1 used a defined conversion of the Onan horizontally-opposed twin. Converted engines were sold by Quickie Aircraft Corporation to Q1 builders. The conversion was not available on the open market, nor were there plans available to do it, as best I recall. You bought the engine, ready-to-run, from Quickie Aircraft. The examples flying on the myriad of different motors since QAC shut down are one-offs by their respective builders. There isn't a new "baseline" engine for the Q1, although some conversions may be more common than others. Keeping an orphaned design flying is not the same as providing for a new, ongoing product offering. Hot Wings Grumpy Cynic HBA Supporter Log Member The Big Twin is no more. Basically there are 3 options for the industrial engine: Convert an existing horizontal shaft engine for direct drive. Probably the simplest. A prop extension can be a simple bolt on. Convert a vertical shaft version. They are cheaper for the base engine but will require oil and carb modifications. If you are messing with the oil system it is not that much more to invert with a dry sump. Convert a horizontal shaft with a PSRU. If you go this way there is no need to invert for prop clearance. It all comes down to what airframe and what mission which way is the best compromise. It looks to me like Boku's project is in the grey area between needing a PSRU or not. Hephaestus Well-Known Member Keeping an orphaned design flying is not the same as providing for a new, ongoing product offering You could argue that - but people were selling plans for the Rotax super quickie mod for decades. Arguably there's possibly more Q1 aircraft starts since qac ceased. As long as you're not pulling a bd5 where really only one possible engine exists/fits/balances... Victor Bravo Well-Known Member How many Lucioles and SD-1's are flying now with more-or-less stock horizontal direct drive V-twin engines? I think dozens. If Bob's airplane has Luciole or SD-1 performance, he'll have a winner. And there are already quite a few brain cells from this forum alone that are capable of defining and offering viable solutions for the ignition. I'm absolutely certain that there are existing car/kart/boat tuner ignition systems available that would not need a whole lot of modifications to run one of these engines. Ross Farnham and others are easily capable of developing a system that would be done and ready for sale by the time Bob's prototype is built. Kohler and perhaps others are already offering fuel injection on V-twins for the mass industrial market. So that stuff is reasonably close to being off the shelf. Para-Zoom in Germany does indeed make a production Briggs derivative that will fit on Bob's airplane, plug and play. It even has a redrive, but again I believe this weight can be saved. BoKu Pundit HBA Supporter I dunno. I just did a re-sketch with the lower thrust line of an upright direct drive engine, and the aesthetics are meh. Also, the undercarriage has to get a lot longer to give good prop clearance. I'm still inclined to go with the redrive. Edit add: I like the looks of the Para-Zoom engine, but it looks like it's based on the big block Vanguard, and I think I need something more compact. TiPi Well-Known Member Log Member What is the best way to tune an industrial engine to accomplish this? Mostly just cleaning up the sharp edges in the intake manifolds. Carburetors are very primitive and depending on the setup, don't provide a steady fuel/air mixture. I'm just going through my initial testing and found the mixture to be very variable at no-load speeds (+/- 1.5 AFR), should see shortly how that is under load. Re-jetting might be required to get the mixture closer to ideal (slightly rich at full power). Some engines might benefit from re-profiling camshaft lobes (shorter duration) but most industrial engines have a very flat torque curve between 2,500 and just over 3,000rpm. plncraze Well-Known Member HBA Supporter Use a redrive. You will love yourself for it later. Most of the flying this thing will be doing is in the speed range where you will like the extra thrust. Vigilant1 Well-Known Member Lifetime Supporter ...if you're considering series/kit production Bob, I think I'd go for something a little more mainstream, like a Hummel/Casler 1/2 VW. Yeah, the jugs stick out the sides of the nose, but you (or your customers) can buy complete, ready-to-run engines and not have to mess around with converting their own. The alternative is the Valley Engineering "Big Twin" V-twin conversion - same deal, you get complete ready-to-run engines. I don't think "generic" V-twin conversions have become "settled" enough for prime time, in terms of a design that will see a series run, even as a kit. For a one-off? Absolutely a viable choice. There is also the option of buying the SE33 kit from Spacek ( I.e. Minisport. That's a 30hp 810cc B&S with all the parts and instructions needed to mount it horizontally and add the prop. Customized flywheel, oil sump, etc, etc. It is sold to SD-1 builders with a cowling, engine mount, and prop. Last I checked (a few years ago) the whole package price was about$5500, but leaving out the prop, engineount, cowling, etc would be expected to reduce the price. Weight of engine reportedly 70.5 lbs.
Spacek is working on a heads-down version (prop on flywheel side) and TiPi is working on a heads-down PTO version. Obviously, the heads-down version gets the prop mounted higher within a conventional cowl outline.

But, I agree that for a turnkey "it is in that crate, put a prop on it" answer, a Casler 1/2 VW would be less fuss.

Last edited:

Vigilant1

Well-Known Member
(Duplicate post).

Victor Bravo

Well-Known Member
sorry double post

crusty old aviator

Well-Known Member
You can thank Harold Morehouse for inverting aircraft engines...oops, I guess this is a bit OT.

2