Engines. A Discussion.

For those not familiar, the gearbox I mentioned above is 3:83 gear reduction with a sprague clutch. No belts. And an absolute marvel of engineering in my opinion.

Before someone asks: (or laughs) these pictures are from the beginning of my engine build and the engine mount pictured is only a mild steel temporary mount so I could R&D where to run my cooling and such while my engine was EXACTLY where it needed to be.
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Engine is awful high being way out front... gonna be hard to see...


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Mike,
You do have a valid point, and I have considered lowering, but haven’t made my final decision yet. The problem I face is that I have a radiator and intercooler underneath, so I tried to give myself room.

What I will say is that those pictures are deceiving. The prop flange is only 6” forward from the 320 ring gear, and actually center of prop is lower as well. The engine itself being so small makes it look much more drastic than it is.

Also, I’m doing a carbon cowl of my own design (nosebowl was just a visual aid) and it hasn’t wiped out visibility as bad as you would think.

All of that being said, I still agree with you and might have to rethink a couple things.

100 lbs less? Good for a long mount PA12.

Bring the engine back 12 inches and put 100 pounds of steel in the cowling...






Joking. I'm just jealous of the weight / hp.
Can't wait to see that thing fly!

If you cowl it right you should have better effective visibility...


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Oli,
I’m glad you’re jealous! I’ve been jealous of your suspension idea all year, now we are even!

ops

I can't wait to see it fly! I've wondered for a while now, why there aren't more Yamaha engines in the air. I know a lot of people, especially the older crowd balks at the idea of a snowmobile engine in an airplane, but these Yamaha motors are simply amazing... capable of insane power, stupid reliable, lightweight, and affordable! I've wished for a while now that Yamaha would tool up and build an airplane-specific version of either the Apex, or the 3 cylinder Sidewinder motor.
Good on you for taking this project on, can't wait to see what you come up with for cowling. Keep us posted!

YamaCub, is it your understanding that that one-way clutch makes prop inertia moot?

1934A said:

.... can't wait to see what you come up with for cowling. Keep us posted!

Click to expand...

Skywalker,
The addition of the centrifugal clutch was primarily to reduce the impact forces of startup/shutdown on the engine/PSRU. when starting the engine, it freewheels, then engages shortly after. The Apex has an internal gear reduction and a rubber dampener which helps a LOT with torsional vibration, and the sprague in the gearbox helps out a lot allegedly as well. I don't claim to be a physicist, but the theory makes sense.

Now that this is died off a little I’ll jump in my two cents. I was down to Gainesville Texas to the Lonestar Stol with my carbon cub. I stood on the sidelines after was my turn to fly, and watch Steve Henry and his Highlander. I stood there thinking exact same thing that you thought Stewart. How Will this engine work in an amphib 185 with a long prop. You can watch him takeoff on YouTube, but it was nothing like being that this is to go from 0 to 10,000 in just a blink.


He had a fall blade fixed pitch prop on it for the competition. The nitrous oxide addition and something through the performance and you can plainly hear when he pops in the nitrous.


I think we’re on the verge of seeing a new kind of engine takeover of this industry. Not sure that the Apex is it for all applications but apparently somebody does, he had two new engines in his trailer he was delivering to Folks in TX. Steve Pierce do you have something to tell us?


Either way it was a real treat to see it and to see steve Henry was a good stick


Jim

This kind of tech is available in the new 140hp Rotaxes, but they are so expensive adding nitrous and extra boost is a big step. The main thing Yamaha brings to the table is now we have an almost free Chevy small block that can be hopped up without any investment to protect.

CamTom12 said:

Charlie’s already made the point, but yes.

You’d have to add a reduction drive, but 300hp is 300hp. The RPM that power is made at only matters for the gearing required to get it to the ground (or to the prop, in this case).

On a PowerStroke forum a while back there was a great discussion about this, complete with math. The bottom line is that a 400hp v8 gas engine (when properly geared) can pull a load up a mountain equally as well as a 400hp diesel.

Click to expand...

Painfully reminded about this thread recently.

I disagreed when I first read it, and disagree more than ever now. Muscle car types, and engineers frequently cite horsepower as the measuring stick to motivation.
To me, it's a useless data point without torque and rpm figures, where the 3 intersect is where the magic happens.. and every time I trust the motor heads or engineers it costs me. If I never hear a hyped up horsepower figure again, it'll be too soon.

I will offer my latest experience, chew on it, agree, disagree shoot it down or not. I'm ok with any of it, because for me, first hand experience always trumps what the books (or screen) say....

Our nurse rigs for the spray service were long in the tooth International 4700's (DT466) pulling fairly heavy trailers. Not much horsepower, but decent torque. Good workhorses, but time to update.:roll: (why am I messing with a good thing?)

Since the current employee pool is limited, I thought I'd try and make at least the actual driving part of a load rig more user friendly. So we opted to build up a few goosenecks in to Heli and fixed wing support systems.

For trucks we figured probably any flatbed 1 to 1 1/2 ton diesel would suffice. I am not terribly brand loyal, as I have owned diesels from all the major players, had gems from each brand, and lemons as well.

When the first trailer got close I went to the dealer alley (hate that task) and there stood a single cab dually C3500 cab chassis with a 6.6 gas engine. Being a full $12K cheaper than any diesel counterpart, and having a heck of a horsepower salesman in front of it, it caught my attention. Now days crew cabs and 4wd are so popular that finding cab chassis on the lot in a single cab are pretty rare. So that box was ticked, dually - check, 401 horsepower - check (I thought). I thought... what the heck? Maybe the gassers are getting better.

Did the deed, and ran the truck to the bed dealer for a flatbed, and initial impressions were, man.... this thing has pep. (of course that was empty). When the bed was done I ran the truck to pick up gooseneck number two, and things were starting to get a little concerning. These trailers are not terribly heavy empty @ 35' and 7000# +/-, and although chassis wise the truck was handling it just peachy, hauling wise it was already feeling the load.

With the first trailer mostly done, we hooked on and took it out for a small Heli job. Empty but with equipment on (how it normally goes down the road) it was just shy of 10,000#. Not much of a load for most one ton trucks, and this one was pulling it, but not in a fashion you'd want to call a daily driver.... uh boy. 2000 gal. water, 500 gal. fuel, and a pallet or two of chemical on board and this truck would not catch up to a moped going down the road.

Now for those numbers types (or CDL guys) on board, yes this is way over gross for the truck / trailer, but this is not how it goes down the road, it's how it sits at the side of a field to load planes / helis. It does have to move from border to border, or ditch bank to ditch bank though, and it needs to do it without coaxing. Immediately I thought I had made a huge mistake moving away from the old 4700's, and had expected too much out of a lowly 1 ton.... what a sleepless night.

The following morning, just to put my mind at ease, I backed my personal daily driver up to the very same trailer. Which currently is a 2018 Ram 2500 / Cummins (370 HP). I went ahead and loaded it all up, and proceeded down the strip. Chassis wise the truck knew it was heavy, power wise you could have had an empty bed and no trailer and it would have moved on down the road just about the same. Wow! I've never had such a wonderful relief provide such a disappointment at the same time. Had we not already cut and welded on the Chevy, I would have dumped it right back on the dealer. I did phone him, because it was his hyped up horsepower conversation that tipped the purchase in the gasser. turns out a local grower had ordered 2 more 1 ton chassis cabs with D-maxs, but backed out due to Covid slow downs. Needless to say, I dragged a trailer down there before moving forward on those. They hauled the load as good as the Cummins. Probably would be a little more highway friendly with the 10 Spd tranny, but that's not a regime ours will ever see.

Unfortunately they are 4wd crewcabs, but we were able to take advantage of some savings as a result of the initial order being balked.

SO bottom line;

Gasser ; 401HP 464 #ft. Torque I wouldn't want to depend on this engine to haul this trailer down the road empty, let alone packing the full load.

Dmax ; 445 HP 910 #ft.Torque Hauls the load exceptionally well. Time will tell if it lasts as long as the DT

Cummins; 370 HP 800 #ft. Torque Would haul the load day in day out no problem. I would have just as easily bought all Rams.

DT466; 350 HP 860 #ft. Torque Hauled the same load for 20 years at friends spray service and never felt it.



As I said at the start. you can agree, or not. But as long as the new flagger truck (the gas powered chevy :roll is in the fleet, anyone is welcome to come by and validate their own theories :lol:

Take care, Rob

Just to throw some gas on the fire....

My brother's A65 was found to have zero lbs of compression on one cylinder and my dad's old O-320 had a dead cylinder before rebuild. These planes flew around for many dozens maybe hundreds of hours low on compression and low on power but happily chugging along. Think these Rotax and Yamaha engines will do the same? My experience from working in the power sports industry and working on sport bikes, snowmachines, and ATV's says probably not. I've seen quite a few 4 cylinder engines just like the Apex engines with thrown rods and camshafts thrown through the valve cover by valves hitting the piston. My guess would be that when they go, they go explosively whereas a Lycoming would chug along making metal and being low on power. Especially once you introduce forced induction things get far more reliant on mechanical perfection. Seems like I've seen quite a few videos of Rotax's being forced down for head gasket leaks or stuck valves...

Just throwing it out there to see what the Apex/Epex apologists have to say.

Oh and no replacement for displacement? Yes but also no...In the air there are no free lunches and with that extra displacement comes added fuel burn, larger tanks, larger wings to lift it all, more weight, more power to lift that weight and around we go...

FWIW, as the son of an engineer, the math and science behind this is not lost on me. I understand it painfully well, even the thought process behind statements like 'horsepower is horsepower' that's that whole semantics and statistics thing.....and with statements like that you are conveniently leaving out part of the equation....and yes there are plenty of examples such as dirt bike hill climbs and tractor drag races. I just believe that just because something is mathematically or scientifically possible doesn't necessarily make it the best choice.

My flying world prefers a more logical approach. My cub has been happily motoring along for 65 years. I hope to see my grandson fly it.

I wonder how many apexs will even be running in 65 years? If the Water Buffalo, or Yam RD are any indication the future isn't looking too good. And they weren't nearly as high strung. I loved those bikes, and dig the apex, but prefer a different kind of cool in my airplanes. Different strokes....


Take care, Rob

Hi, my name is Pete. I’m a diesel addict.

I grew up on a dairy farm with hard starting tractors in the winter, and sometimes in the summer. Dad had gas trucks for awhile but saw the light and started buying diesels.
I’ve owned a couple gas trucks when I was younger, but last one was a ‘98 F150 and I had two other bigger diesels in the yard.
Point is I’ve spent the last 25 years with a trailer behind me as much as not. I wish I had the current 10 speeds then but push the pedal down and just let the torque roll in. Smoothest way to drive ever invented.

Now imagine if you were cruising down the river at 50 feet and wanted to climb the canyon wall. Just roll the power in and feel it just keep right on pulling you up, without slowing down or changing rpm. I believe that is what diesel power in an supercub would be like.

There’s a place for everything. In Hal’s or Steve Henry’s lightweight machines are likely perfect setups for motorcycle engines. Just as motorcycles are. But if you build aircraft heavier than that, you’re going to need a heavier duty engine. Pick your poison.

Tom always said it was easier to add power than lose weight. You’ve seen the engine on Scrappy, right?


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Farmboy said:

Now imagine if you were cruising down the river at 50 feet and wanted to climb the canyon wall. Just roll the power in and feel it just keep right on pulling you up, without slowing down or changing rpm. I believe that is what diesel power in an supercub would be like.

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Click to expand...

Thank you! This made me think of my wife and smile :lol:. I will try to explain.

First because she has a name for this phenomena ...she calls it the 'tractor factor', and second of all because when we are in the 180 and find ourselves in this predicament , she exclaims "God bless Steve Knopp!" :lol::lol::lol: How could you not love a woman like that

Take care, Rob

Farmboy said:

Hi, my name is Pete. I’m a diesel addict.

There’s a place for everything. In Hal’s or Steve Henry’s lightweight machines are likely perfect setups for motorcycle engines. Just as motorcycles are. But if you build aircraft heavier than that, you’re going to need a heavier duty engine. Pick your poison.

Tom always said it was easier to add power than lose weight. You’ve seen the engine on Scrappy, right?


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Click to expand...

I am one who has little desire to fly behind an engine that was designed when my late father was born and last had any technical improvements when I was born.
I do not believe in the "flew around with no compression" being a good thing sine most all of those situations become headlines.
I do have a turbo Hayabusa powered car, not for road use but it is stupid impressive on a road course.

I will admit the plane I am building will more than likely be powered by a car engine. Just a little 4 cylinder. It will be barely 700# torque at the prop with touch more than 300hp. Just barely enough to get off the ground right. Not much heavier than a big Lyc 4 cyl but will use considerably less fuel so over the hours it will more than average out.
I am starting to consider a diesel engine, just a little German one. 30 years ago I would not run on the highway with one since they had to many head failures and insufficient power to go downhill. Unlike aircraft engines though, these engines today are not the same as when we were born. They are far better rather than far worse.

Thank you for being innovative.

Without guys like you, guys like me couldn't go to the store and by a slatted or slotted wing for their cub.

Without guys like you, questions like the OP don't get answered.

And without guys like you, there would probably be less opportunity for guys like me to enjoy things like a '39 Buick Special complete with a Dynaflash 'Fireball 8' , or flying my neighbor's '29 Travelaire 4000. I giggled like a girl when he let me run his Ariel Square four down to the equipment shed.

I realize the need for innovation and enjoy it. I also feel a need to enjoy the rich history behind these cool things that burn fossil fuels. Before too long your innovation will be old too ;-)


Sooo.... is 300 HP always 300 HP? Sorry for the derailment SB


Take care, Rob

I've had at least one Yamaha 4-stroke sled for 15 years, so I'm no stranger to these motors. Yamaha tried to reinvent snowmachines like MX motorcycles have been. The experiment wasn't successful except in the heavy hauling sled dept and now Yamaha has returned to 2-stroke sleds, which are very different than they were 15 years ago. While Yamaha thought 4-stroke was the answer to emissions problems the other manufacturers went to direct injection 2-strokes, and holy cow do they ever work for the application. Outboards are going on a similar path. So after squeezing the throttle on these Yamahas for 15 years do I think they could power a Skywagon like they do a Highlander? No, I do not. I think the Highlander experiment is fun but next week or next year somebody will adapt a newer motor and the Apex will fall from favor. And maybe that motor is an outboard powerhead, because those are seriously good engines these days. At the end of the day I still believe my initial statement. There's no replacement for displacement. It applies to my truck, car, snowgos, boats, wheelers, and airplanes. And by the way, my little 30hp New Holland will outwork all of them in it's application, and I think application is the key.

I am by no means an expert...however I feel HP is not HP...my exp cub has a hopped up O320 with a little over 180hp...my cub is light and performs well. A buddy has a O360 180hp cub...pretty stock other then the engine being an 0360. We were comparing one day on a gravel bar...we both took off in 80’...however he got to the ground braking mark faster, then also climbed to 500’ much faster. Torque Matters! On another note, if you have any experience with heavy equipment...diesel torque really shows itself here.

HP is not all equal but in terms of aircraft it is almost nearly so. Sure, if you're measuring the torque at the crank on a smaller high revving engine then you will see a lower torque/higher horsepower number but once you run it through the reduction drive you should see almost equal torque numbers as an equivalent direct drive engine. If it can swing the same prop at the same shaft rpm then it's doing the same thing. The only thing that would be lost is the time it takes to get the prop up to RPM which even in an extreme scenario would only be fractionally different between the two theoretical engines.

But it seems as if we're comparing apples to oranges here as the comparisons are between large heavy aircraft that traditionally run direct drive 4 cylinder aircraft engines and smaller light aircraft with new generation gear reduction high revving engines. The only way to settle the issue is to compare a plane of equivalent weight and airframe performance with both engines. A cub would be the closest thing to a straight comparison but I have yet to see an operational EPEX or Rotax in a cub airframe. Maybe the Zlin cubs would be comparable but even there they are much lighter overall aircraft than a proper PA-18.

All in theory, I dont' know for sure but in my head this all makes sense.

I disagreed when I first read it, and disagree more than ever now. Muscle car types, and engineers frequently cite horsepower as the measuring stick to motivation.
To me, it's a useless data point without torque and rpm figures, where the 3 intersect is where the magic happens.. and every time I trust the motor heads or engineers it costs me. If I never hear a hyped up horsepower figure again, it'll be too soon.

Rob, couldn’t agree with you more. 45 years of most things pistons- gas and diesel- pretty quick to learn what does the work and what doesn’t. To keep this thread where it belongs, on airplanes, I offer what I hope is as close to apples v apples as anything here.

I am fortunate enough to have contact with many aircraft, both through work and through a good cross section of friends that own them.
This particular example makes for good comparison. Involves one airframe, “same” but different engine.

So.....Skywagon C-185, stock low time, <500hr IO-520, Sportsman STOL, Aeroset straight floats, not a bunch of whistles and bells, just a nice, well rigged 185. Performance (and we’ll stick with full gross weight loads here, anything else is meaningless for this discussion) was as good as any 185 you’d care to compare it to.

Owner decides it’s time for an upgrade. Now, many of us know the IO-520 is, coincidentally for this discussion, a 300HP powerplant. Not continuous mind you, but 300 nonetheless.
Enter the IO-550 upgrade with its new mount and associated items etc. and it’s 300HP, continuous.

Granted, the 550 is essentially a re-engineered engine, heavier case, beefier cylinders, but that’s all structure and has little to do with “horsepower” or in the real world, TORQUE, other than to be able to withstand the forces generated within the engine so it stays together. The 30 additional cubic inches, as I understand it and correct me please if I’m wrong, was achieved in the stroke being increased. Stroke is huge when it comes to torque.

The only other factor that changed on this aircraft was the delivery of the above mentioned 300 to the air through prop. I don’t have the prop specs handy but the stock 520 had the “standard” 2 blade McCauley.
The upgrade changes it to a 3 blade McCauley. It’s a dramatic change visually as the new 3 blade is quite a hefty specimen with its wide chord blades etc. There’s a whole bunch of engineering that is propellers that I just nod my head and say “yep, good work guys” when it comes to some of that knowledge that I can’t speak to and I’m not going to start here what make one optimum over the other.

Apples to apples nothing else changed airframe wise, load it up with 4 big guys and a bunch of gear and let’s go... Stock setup you’d be likely to see a long run, make it up on step, off you go or, maybe, possibly, a shutdown and taxi back to pitch some stuff out....nah, no ones ever done that...
After the “repower” (remember, still “only” 300 HP), this airplane just flat out DOESNT CARE what you load in it, size of the people, how full the floats and bag pit are with “normal” gear and supplies.
It comes out of the water up onto the step like a shark is after it and accelerates like a funny car, off the water and gone. Dramatic change. Very impressive.

More gas for the fire? Maybe but horsepower? Pffftttt! TORQUE is what makes it all happen. No replacement for displacement making torque.

My experience with something relative I hope, thanks for your collective knowledge,

Cheers, Oz

Has anybody actually dyno'd an ePex engine at the crank or at the gearbox PTO? Did some searching and there are no independently published numbers as far as I can tell. I see that Edge rates them for a particular horsepower but for this discussion we need crankshaft torque numbers at peak HP and how that translates through a gear reduction (which would multiply torque). The closest I can find is the Yamaha snowmachine dyno charts which show about 110ft/lbs at a screaming 7000rpm which through a reduction gearbox of say 3.83:1 would result in 421ft/lbs no accounting for mechanical losses and the fact that they probably don't run them at peak RPM. Even with significant losses and running at a lower RPM setting I would imagine that post-gear reduction the torque is still very similar to a direct drive Lycoming running at a lower RPM.

Lots of this is redundant as I see a few are saying the same things on each side of the fence, in our own way.

But in flying, I believe like pulling a trailer, load matters. A car or bike at speed uses what, 10% of its rated hp to maintain speed?

Enter drag, weight, etc - as stated above, torque doesn’t care much because that’s what moves it.

Like the Skywagon example above, that stroke that makes the torque moves the load. A friend who owns a 520 bonanza flew a 550 version and said the same thing. Very noticeable! [emoji16]

Perhaps I’m wrong but it would be interesting to play with edge apex stuff in an RV4/8. Light, fast, no drag.

For hard numbers on Apex stuff I’d reach out to Jason Busat at Badass Powersports. He’s in tight with the Edge group from Norway.

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CamTom12 said:

I’m not personally aware of any reduction drives that can take hydraulic CS props. There must be some out there though. Wasn’t the guy building the Raptor canard plane using a 300-something hp diesel car engine and a hydraulic CS prop?

Click to expand...

There are a few Seabees flying with LS1/LS3 conversions with Hartzell or MT props (reversible!)

OzAK said:

I disagreed when I first read it, and disagree more than ever now. Muscle car types, and engineers frequently cite horsepower as the measuring stick to motivation.
To me, it's a useless data point without torque and rpm figures, where the 3 intersect is where the magic happens.. and every time I trust the motor heads or engineers it costs me. If I never hear a hyped up horsepower figure again, it'll be too soon.

Rob, couldn’t agree with you more. 45 years of most things pistons- gas and diesel- pretty quick to learn what does the work and what doesn’t. To keep this thread where it belongs, on airplanes, I offer what I hope is as close to apples v apples as anything here.

I am fortunate enough to have contact with many aircraft, both through work and through a good cross section of friends that own them.
This particular example makes for good comparison. Involves one airframe, “same” but different engine.

So.....Skywagon C-185, stock low time, <500hr IO-520, Sportsman STOL, Aeroset straight floats, not a bunch of whistles and bells, just a nice, well rigged 185. Performance (and we’ll stick with full gross weight loads here, anything else is meaningless for this discussion) was as good as any 185 you’d care to compare it to.

Owner decides it’s time for an upgrade. Now, many of us know the IO-520 is, coincidentally for this discussion, a 300HP powerplant. Not continuous mind you, but 300 nonetheless.
Enter the IO-550 upgrade with its new mount and associated items etc. and it’s 300HP, continuous.

Granted, the 550 is essentially a re-engineered engine, heavier case, beefier cylinders, but that’s all structure and has little to do with “horsepower” or in the real world, TORQUE, other than to be able to withstand the forces generated within the engine so it stays together. The 30 additional cubic inches, as I understand it and correct me please if I’m wrong, was achieved in the stroke being increased. Stroke is huge when it comes to torque.

The only other factor that changed on this aircraft was the delivery of the above mentioned 300 to the air through prop. I don’t have the prop specs handy but the stock 520 had the “standard” 2 blade McCauley.
The upgrade changes it to a 3 blade McCauley. It’s a dramatic change visually as the new 3 blade is quite a hefty specimen with its wide chord blades etc. There’s a whole bunch of engineering that is propellers that I just nod my head and say “yep, good work guys” when it comes to some of that knowledge that I can’t speak to and I’m not going to start here what make one optimum over the other.

Apples to apples nothing else changed airframe wise, load it up with 4 big guys and a bunch of gear and let’s go... Stock setup you’d be likely to see a long run, make it up on step, off you go or, maybe, possibly, a shutdown and taxi back to pitch some stuff out....nah, no ones ever done that...
After the “repower” (remember, still “only” 300 HP), this airplane just flat out DOESNT CARE what you load in it, size of the people, how full the floats and bag pit are with “normal” gear and supplies.
It comes out of the water up onto the step like a shark is after it and accelerates like a funny car, off the water and gone. Dramatic change. Very impressive.

More gas for the fire? Maybe but horsepower? Pffftttt! TORQUE is what makes it all happen. No replacement for displacement making torque.

My experience with something relative I hope, thanks for your collective knowledge,

Cheers, Oz

Click to expand...

Not to burst your bubble, but he 550 is 310 hp for take off.

Also, again everyone's focus is on the engine, which is important, but forgets the key element is the transfer of the power to the drive, (Stewart mentions this). In sleds it is to the track, planes to the prop and amount of wind you send backwards- different props on the same engines make a world of difference, and different at different phases of flight!

We play around with sled clutching all the time. Tuning an engine to run at the proper RPM will make something feel like a dog, or run like a race horse. Yes, even big gas engines.

I trust Yamaha engines far more than I do Chevy and ford. Lets home we see more R&D