An example Kohler

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
6,982
Location
US
I do not offer this as a way to use a vertical shaft engine on and aircraft, just an example of how it's been done in hovercraft and airboats.
They use a v belt and two extra pulleys for hte 90 degree change. The belt is long enough it can twist easily. I'm not sure how one would tighten this configuration up the be a front-mounted tractor engine.

View attachment 115980 View attachment 115981
Getting a bit off track from karmarepair's Kohler, but...

The hovercraft/long, twisted belt angle drive could work with an internally mounted engine (they are using the stock fan) and belts to a fan in each wing (LE or TE). It would be a bit like the the setup on a plane Matt posted about several months ago. Plenty of disk area that way, would work best for low speed, low power flight. It worked for the Wright brothers...
 

karmarepair

Well-Known Member
HBA Supporter
Joined
Jan 13, 2011
Messages
677
Location
United States
I do not offer this as a way to use a vertical shaft engine on an aircraft, just an example of how it's been done in hovercraft and airboats.
They use a v belt and two extra pulleys for the 90 degree change. The belt is long enough it can twist easily. I'm not sure how one would tighten this configuration up to be a front-mounted tractor engine.

View attachment 115980 View attachment 115981
You only get one belt, so you're limited in the amount of power you can transmit. Shades of the Corvair fan belt. Any links to anybody's plans, or discussions? I'm particularly interested in the configuration of the idler pulleys. It definitely has possibilities for a CGS Hawk/Stojnik S-2 style low keel boom and pod type airplane.
 

BBerson

Light Plane Philosopher
HBA Supporter
Joined
Dec 16, 2007
Messages
15,363
Location
Port Townsend WA
Somebody used that 90° belt on a powered chute about 10 years ago. (old yahoo small engine forum).
 

Lucky Dog

Active Member
Joined
Aug 4, 2021
Messages
38
We've been flying a Vanguard model 38 for almost three years now and it's golden. I'd suggest ditching the direct drive concept, though. Redrives are actually a simpler solution than adapting an industrial engine to direct drive. Any light weight modern engine will run near or above 4500 to achieve adequate power. That's why Rotax gears the 912. Plus, lots of tiny power pulses coming from lightweight engine components don't dash propellers to pieces.
 

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
6,982
Location
US
We've been flying a Vanguard model 38 for almost three years now and it's golden. I'd suggest ditching the direct drive concept, though. Redrives are actually a simpler solution than adapting an industrial engine to direct drive. Any light weight modern engine will run near or above 4500 to achieve adequate power. That's why Rotax gears the 912. Plus, lots of tiny power pulses coming from lightweight engine components don't dash propellers to pieces.
If I may ask:
1) What type of redrive are you using and approx how many hours do you have on it?
2) Have you measured the HP you are getting, or do you have an estimate (max, cruise)?
3) What is your cooling/baffling setup, and the experience you've had with CHTs?

Thanks.
Mark
 

Lucky Dog

Active Member
Joined
Aug 4, 2021
Messages
38
@Vigilant1: 100 hours so far. We're not concerned about the engine. Teardowns show zero wear or stress on the moving parts. We are more interested in the drivetrain and mounting parts going forward. Redrive uses four 3VX V belts at 1.67:1. The engine drives a Quicksilver single place, and thus is limited to a 52"propeller. Using a PSRU multiplies the torque, and allows the host engine to produce its maximum power at exactly the RPM you want to spin the prop.

We use a three blade Ultraprop at 15 degrees. Using the Ultraprop graph as a reference, we get 33/34 hp at 4500 rpm (measured at the propeller) at a pressure altitude of 5000 msl. Dyno tests at the crankshaft will show a higher number, but all that counts is how much torque is available to move air. The airplane's performance closely approaches the Rotax 447, so our figure is honest. (Remember, we're measuring HP at the prop, where the mighty 447 would not reach its advertised numbers either.) Similarly modified model 38 engines are available off the shelf with (dyno-tested) power outputs of 35 to 40 hp. Impressive, considering it starts at 23 hp.

Fuel burn is 1.8 gph and the engine never runs hot. Even on 100-plus degree days, the CHT rarely hits above 300f. Engine tune is mild: seven-degree advance on the ignition, stiffer valve springs, smoothed out casting roughness in the cylinder heads, and we switched to a cam that raises the torque to peak near 4500 rpm. We also jet the carb one step richer (#112, both sides). High compression pistons (about 90 bucks each with rings) would further increase torque, but we left them out because we wanted to minimize the engine mods to see how far we could get without going on a spending spree or exceeding garage-mechanic skillsets. Oh, and flat tappet engines absolutely need zinc-based racing oil to run long and hard. We run Valvoline VR1 20/50.

Because the Quicksilver flies slow, we left the stock fan shroud (4 pounds) and flywheel (14 pounds) in place, but it's doubtful that it needs the big fan. A smaller, 6-pound aluminum flywheel from ARC racing is the go-to for mower racers, who say that their highly modified model 38s are still hard to keep warm enough to attain maximum power. Quicksilvers are probably the draggiest bird in the sky, so this little Vanguard could easily push or pull a more efficient plane around at speeds beyond FAR 103. In that scenario, I'd suggest a 1.8:1 reduction spinning a 60 inch prop. I'll report back on that later this year as we are putting this configuration in motion now.

Generally, we chose the Vanguard model 38 because it is one of the lightest V twins in its class, it's made in Japan, it holds up well in racing configuration, and there are many performance upgrades available. We prefer 3VX v-belts because they won't jump the pulleys if they get slack. Micro-v drives, however, can be more compact and lighter weight - plus, the pulleys seem to wear longer. All reasons why they have become the go-to, but alignment must be more precise (thin, wide belts) and the 5mm groove requires spot-on tension. Ace Aviation has a well-designed, lightweight micro-v redrive, made in India, that bolts right onto Industrial V-twin's universal face-plate pattern. Most good belt-drive PSRUs run around 800/900 bucks - which we discovered, is a fair price.

So, that's a lot of words, but it seems most pilots in this forum are looking for hard answers and we've been doing this for a while.
 
Last edited:

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
6,982
Location
US
Thanks for the information, Lucky Dog. Looks like it is working great for you.
@Vigilant1:
We use a three blade Ultraprop at 15 degrees. Using the Ultraprop graph as a reference, we get 33/34 hp at 4500 rpm (measured at the propeller) at a pressure altitude of 5000 msl. Dyno tests at the crankshaft will show a higher number, but all that counts is how much torque is available to move air. The airplane's performance closely approaches the Rotax 447, so our figure is honest. (Remember, we're measuring HP at the prop, where the mighty 447 would not reach its advertised numbers either.) Similarly modified model 38 engines are available off the shelf with (dyno-tested) power outputs of 35 to 40 hp. Impressive, considering it starts at 23 hp.

Fuel burn is 1.8 gph and the engine never runs hot. Even on 100-plus degree days, the CHT rarely hits above 300f.
As another check, if we assume a BSFC of about .40 - .45 lb/hp-hr for these little air cooled, pushrod, carbed engines in normal use, 1.8 GPH works out to 24- 27 HP over the whole measured period. You probably lose about 1 HP of that to the fan, but that (IMO) is a small price to pay for the excellent CHTs you are seeing. At the low speed a Quicksilver flies (thus, the low static pressure available to push air through the fins) the engine fan may be a nice thing to have. Are you measuring CHT under the plug, or somewhere else?

FWIW, I'm pretty sure that all the Vanguard V-twin engine production has been moved from Japan to two factories in the US (Statesboro, Georgia and Auburn, AL).

Engine tune is mild: seven-degree advance on the ignition, stiffer valve springs, smoothed out casting roughness in the cylinder heads, and we switched to a cam that raises the torque to peak near 4500 rpm. We also jet the carb one step richer (#112, both sides). High compression pistons (about 90 bucks each with rings) would further increase torque, but we left them out because we wanted to minimize the engine mods to see how far we could get without going on a spending spree or exceeding garage-mechanic skillsets.
It does sound like the decisions you made are working out. Thanks again for the information, and let us know how the project develops.
 

Lucky Dog

Active Member
Joined
Aug 4, 2021
Messages
38
I like the v-belt idea. What is the flying weight with 14 pound flywheel, belt drive and starter/electric system if installed?
@BBerson: 76.8 pounds for the engine. The Quicksilver uses a shaft drive, most of which we remove. Our QS drive (pictured) looks similar, but is three pounds lighter. The weight of our alternative 1.8:1 belt drive is 9.8 pounds (not shown), including the hardware and we're using a steel drive pulley. Drives are available that weigh less - between seven and eight pounds. The goal is to provide a more affordable four stroke engine to replace the small Rotax two strokes that have been phased out. If all goes to plan, the first QS mounts and drive kits should be available by Spring 2022, along with plans and sources for the engine mods. It's super simple to install.
 

Attachments

Victor Bravo

Well-Known Member
HBA Supporter
Joined
Jul 30, 2014
Messages
9,866
Location
KWHP, Los Angeles CA, USA
It just dawned on me that the Quicksilver I had seen flying (which I had mentioned in a previous HBA thread) is probably the same one Lucky Dog is involved with. I guess I failed to mention that because the hangar where the Quick was located is not the same hangar where I met Lucky Dog and saw his original design airplane. So I didn't put two and two together.

I saw this airplane fly a year or two ago, and it looked/sounded/moved with good authority.
 
Last edited:

karmarepair

Well-Known Member
HBA Supporter
Joined
Jan 13, 2011
Messages
677
Location
United States
@BBerson: 76.8 pounds for the engine. The Quicksilver uses a shaft drive, most of which we remove. Our QS drive (pictured) looks similar, but is three pounds lighter. The weight of our alternative 1.8:1 belt drive is 9.8 pounds (not shown), including the hardware and we're using a steel drive pulley. Drives are available that weigh less - between seven and eight pounds. The goal is to provide a more affordable four stroke engine to replace the small Rotax two strokes that have been phased out. If all goes to plan, the first QS mounts and drive kits should be available by Spring 2022, along with plans and sources for the engine mods. It's super simple to install.
REALLY interesting.
I like the way the whole engine is hung on elastomeric isolators.
I THINK this is true - the long shaft driving the prop is torsionally soft because of its length, and thus has a very low resonant frequency. So the prop's inertia is isolated from the engine/flywheels Moment Of Inertia.
I'm interested to see what Lucky Dog does with a tractor installation.
 
Top