Inverting a G13bb

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I thought about this some before I decided to go down the path of the inverted B+S for my Quickie......though with the 1.0L for direct drive.
Your biggest problem will likely be the high placement of the oil pump in the inverted position. Making an adapter to put an oil pump on the distributor end of the camshaft might be a viable option?
 

TFF

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When Steve Wittman converted his Olds 215, he had to turn the valve covers into the oil drain back recovery. I believe he channeled it to a different sump. That essentially became the new oil pan system. The other end of the problem is oil pickup. New sump has to be plumbed to where the engine oil pickup is to supply the oil. Except for a pump to suck oil out, it’s kind of half a dry sump system. You have to decide if that works or you need to go real dry sump.
 

aeromomentum

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We have dyno'ed 100's of Suzuki G series motors and the torque curve is very flat from about 2900 to 6000 rpm. At about 2800 rpm we have recorded just over 50hp and at 3300 rpm we have seen from 60hp to 65hp. Keep in mind that we do not optimize for these RPMs.

We have thought about a low cost, light weight direct drive version but we will not be doing this. The oil pump is concentric with the crank. As long as the oil pump does not loose prime it should be able to pull the oil up from the valve cover if the engine is inverted. Of course this would require a new valve cover/oil sump. There is nothing internal in the engine to prevent oil from draining into the valve cover it the engine is inverted. I would slightly worry about valve stem lubrication when inverted.

Two other issues are the thrust bearings and the crank loads due to the prop moment of inertia. The moment of inertia limit on the prop would need to be very low. The thrust bearing is at the middle of the crank, is half round and is not directly pressure lubricated. It relies on the oil spilling out from the center main bearing bearing.

The weight of the G13 as we use it but without the gearbox is about 150lbs. So for about 20 more lbs we can about double the power and thrust.
 

ToddK

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Not direct drive. That had not not even occurred to me. My thought was inverted with a gearbox. I like the engine in the vertical orientation, and my project is pretty narrow. Upright with a tall gearbox would be ideal but such a thing does not exist.

I found this guy who converted his to a dry sump, but that might not be necessary with redesigned valve cover.
 
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mm4440

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When Steve Wittman converted his Olds 215, he had to turn the valve covers into the oil drain back recovery. I believe he channeled it to a different sump. That essentially became the new oil pan system. The other end of the problem is oil pickup. New sump has to be plumbed to where the engine oil pickup is to supply the oil. Except for a pump to suck oil out, it’s kind of half a dry sump system. You have to decide if that works or you need to go real dry sump.
The BOP V-8s oil pump was mounted on the front cover making it easy to re plumb the oil inlet.
 

mm4440

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Not direct drive. That had not not even occurred to me. My thought was inverted with a gearbox. I like the engine in the vertical orientation, and my project is pretty narrow. Upright with a tall gearbox would be ideal but such a thing does not exist.

I found this guy who converted his to a dry sump, but that might not be necessary with redesigned valve cover.
A tall redrive to get the prop shaft were you need it to be is the best solution, in my opinion.
 

aeromomentum

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We are working on a large offset gearbox for the Suzuki engines and are waiting on gears from our gear supplier. While this allows the engine to stay upright it really is not that much narrower. Keep in mind that our 70 degree slant engine is 23.6" wide and our upright version is 21" wide. Of course the reason for our slant version is get the prop closer to the top of the engine.
 

Martti Mattila

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Save your self and put in upright with re drive. I saw inverted air cooled NSU Prinz four cylinder in S. A. magazine in early eighties, start serious work with it in 2017 spent one winter as a full time job. A lot of work and thinking, I re learned a lot from all the aspects of engine desing, dry sump oil pump is on the end of overhead cam shaft. Dual ignition, stroked crank 78 mm. original 66,6 mm. Motorcycle barrels, Masda piston. Barrels must go high in the case to make cutters for oil. Distributor will have new shorter version to make space for prop. Now I have 90mm. stroke shaft for next version but still it is pure stupidity to build something like that and very few is able to. It has run once with starting spray, oil return to oil tank needs improving. Maybe Nascar dry sump pump. Occupational school background as a car mechanic. I got so many projects and I am 69.
 

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rotax618

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I have done some experiments with the G10 engine and gear reduction. To get a low cowl profile I first tilted the engine over at 90 deg, but found the oil in the valve cover couldn’t return fast enough without a large tube from the valve cover to the modified sump -
I found that tilting the motor over at 70 deg there were no oil return problems and there was room above the engine for a carburettor and alternator. The gearbox was an SPG2 but I made an adaptor plate to fit a Rotax E gearbox, the Rotax starter would start the G10 and the installation was lighter than the SPG and Suzuki starter
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mm4440

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I have done some experiments with the G10 engine and gear reduction. To get a low cowl profile I first tilted the engine over at 90 deg, but found the oil in the valve cover couldn’t return fast enough without a large tube from the valve cover to the modified sump -
I found that tilting the motor over at 70 deg there were no oil return problems and there was room above the engine for a carburettor and alternator. The gearbox was an SPG2 but I made an adaptor plate to fit a Rotax E gearbox, the Rotax starter would start the G10 and the installation was lighter than the SPG and Suzuki starter
View attachment 121123 View attachment 121124
Well done. Do you have a total weight?
 

rotax618

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It was 14 years ago and I have moved twice, sorry my notes have been lost. If I remember correctly the bare G10 with a lightened flywheel was only a little heavier than the 618 I had. I sawed up the inlet manifold and welded a tube to mount a Bing Carb off a Jabiru (1 1/4” I think). My G10 had raised compression and a cam grind, used the stock pointless distributor and coil. The Suzi produced nearly the same thrust as the 618, the only reason I didn’t use it was I got a 912 quite cheap and it fitted the cowl better. His is a photo of a B2 engines G13 laid horizontal.
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wsimpso1

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Two big parts of running auto engines direct drive is that the crank and support bearing systems are not designed to carry:
  • Gyroscopic moments for Prop Mass Moment of Inertia times rotation speed time combined pitch yaw speed;
  • Thrust loads from the propellor
The successful direct drive Corvair engines all have beefed up prop end pieces, and Steve Wittman put a separate bearing set and prop shaft out front. Both were designed to carry gyroscopic and thrust loads. By the time you have the bearings and shaft to do this, you are already half way to the geared system... And they are out there for these size engines.

Billski
 

rotax618

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A 4 bearing 3 cyl or 5 bearing 4 cyl crank should be strong enough if driven off the flywheel end, provided they are not fitted to an aerobatic aircraft. Of course they require some sort of a flywheel the tame TVS.
 

wsimpso1

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should be strong enough...

I have a bunch of professional background with this whole area of the gadgets right after the crankshaft flange and with torsional vibration.

Car/truck combined assemblies of flywheels/flexplates, clutches, dampers, and torque converters:
  • Have significantly less flywheel effect than propellors, and much less effect per pound. MMOI is the sum of dm*r^2. A prop bolted to the flange has a lot of its weight at much larger radius than a flywheel. When the prop is mounted to the flange, more flywheel effect is best added with a heavier prop;
  • Are supported against all dynamic loads at both the engine side and the transmission side, so bending moments into the crank are pretty small;
  • Undergo at maximum only about as much combined pitch and yaw speed than props do in abrupt stalls, stall departures, ground loops, and even line-up maneuvering like entering or leaving slips for landing;
I knew our crankshaft engineers. They designed them to (and in order):
  1. Maximum torque loads (which is torsional strength);
  2. Then to have torsional resonance of the installed system at 2-1/4 octaves (or higher) above max firing frequency (which was about torsional stiffness and usually bumps torsional strength);
  3. Then finally to carrying radial load from radial positioning errors (tolerances) of the engine/transmission fit.
Anything beyond these capabilities was excess weight and they really avoid putting in excess weight if they can. The result is usually pretty small bending stiffness compared to a propellor flange on an airplane crankshaft.

Then there is taming vibration. Adding flywheel weight to a direct drive prop system is excess weight:
  • Generally the prop is pretty stiffly attached to the crank flange so the prop accels and decels with the crank on firing;
  • The prop is high inertia per pound compared to a fly wheel because it has a lot more radius (and radius is squared).
What does adding flywheel effect to an engine do for it? It lowers the fundamental frequency of a mass-spring chain. In direct drive airplane engines, they generally try to put the crank resonance well above highest firing frequency, and added inertia in the prop works the wrong way. This is characterized as a "stiff" system.

Now if we want to isolate engine vibration from the output, like with car/truck engine from the rest of the powertrain or airplane engine through gear box to prop, then we have inertia at the engine, inertia at the gearbox and prop, and a deliberately soft element between them. This is intended to pass only a small fraction of engine vibration to the downstream elements. With two inertia and a spring between them to tune, we also have engine idle speed as a variable. We are done tuning these four variables when first resonant frequency is at least an octave below firing frequency at idle. This is a soft system. Prop inertia we can usually only make modest adjustments in, engine side inertia and engine idle speed can be useful to tuning, while spring rate has huge potential. The most popular springs though are taken from either aftermarket engine isolators in manual trans clutches or are driveshaft giubos. In either case, your spring rates and capacities are usually restricted to what is out there unless you have a big budget for development and tooling.

Steve Wittman in his direct drive V-8 used a separate prop shaft and bearing set, and a manual trans isolator. This is a lesson to be learned...

Robust solutions can be had by either beefing up the crank and flange (Corvair) or install a separate prop shaft and isolator. The Rotax, AeroMomentum, and almost all other "successful" geared PSRU also put an isolator between engine and the rest of the system, and tune them to keep resonance below idle firing rate. This was also done in the big inline piston engines of WWII - note the quill shafts driving both the prop gearset and some of the accessories.

Billski
 

ToddK

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Not sure where the no gear box idea came from. It was not mine. A gear box should really be a given on this kind of engine. My original question came down to inverting the engine, and it seems like there are easier solutions. Also too heavy for my project. Trying to keep the weight around 165lbs.

Too bad the Mikron engines are not really available here in the States.
 
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