Rocket 3 engine?

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Aviacs

Well-Known Member
For all the interest in motorcycle engines on homebuiltairplanes.com, i can't find a post with the big size Triumph triples?
(Even thought i asked, once, but can't find a mention)
3 cylinders, 2250 to 2450 cc depending on year, ginormous torque, almost flat curve from 3,000 to 4,800 rpm. Aprox 90 HP at 3,000 rpm, over 100 at 3,500.

Maybe too heavy?
Can't find weight with all the non-essentials removed (gear box, etc). Liquid cooled/needs radiator.
Is there a problem with the vibration signature for airplane?
People remember their HS Bonnies oil leaks & Lucas electrics; or thrown rods in the 750 Tridents, and just still don't trust Trumpets???

smt

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TFF

Well-Known Member
Probably too rare unless you got a totaled bike in the shed.

pfarber

Well-Known Member
There really isn't a need for 100-hp-ish engines. there are many out there that work. Other than being a neat project there would be better starting points.

Aviacs

Well-Known Member
There really isn't a need for 100-hp-ish engines.
Actually seems to be one of the largest categories in which obvious answers are either very expensive ($24,00/Rotax); Expensive and heavy (Continental 80/90/0200) or very experimental conversions and not always optimal weight-wise. My question assumes playing at the occluded end. How would the triple compare. Considering the notion that it looks direct-drive capable. (derated to 80-ish HP) Other than being a neat project there would be better starting points. Such as, based on what parameters? Not really arguing for the motor. Wondering why, since it presents (other than unknown weight) as better than many other options people discuss on here ad nauseum, for something in the VW to C90 range. What engine are you using to fly your BD4, meaning aviation origin power, or "conversion" of some sort? Personally, i want a Pobjoy Niagara. But AFA perfectly viable engines in the 80 - 100 HP range @ 135 lbs, that probably defines "vanishingly rare" & unlikely to be in the economical purchase class. smt Niels Well-Known Member 3000 rpm and 220m/second tip speed means a prop of 1.4 meter. That is to small for 90 hp many homebuilts Aviacs Well-Known Member 3000 rpm and 220m/second tip speed means a prop of 1.4 meter. That is to small for 90 hp many homebuilts Exactly my gripe about 80 HP VW direct drive. Running 52 - 54" props on Sonerais cruising 3400 +/- rpm to attain the HP. If same or more power at lower rpm was available, still probably can't exceed 64", maybe 66" for ground clearance, but even 6o" @ 3,000 has to be a big efficiency gain. (still under 800fps. 3200 is 838 fps, acceptable) People with Jabiru do better, especially the 3 litre 6 banger. Jabiru weight and HP are great, but back in the "less"-economical class. (2200 4 banger = 85HP @ 3,300 rpm/$15,000)

I don't suppose there is a way to answer the 2250cc+ Triumph 3cyl weight question without actually starting to butcher an engine, though.
Was hoping someone had tried it. No, I don't currently own one, have never seen one detached from the vehicle, though have a cellar full of the antique versions in boxes and baskets.

Probably the pertinent Q that could be answered here is "would there be any exceptional vibrations issues" involved with attaching one to the backside of a 2 bladed propeller?

Moving in the direction current respondents seem to want to push: "Imagining a re-drive, are TV issues likely to be greater or lesser compared with a horizontally opposed 4cyl? Inline 4 cyl?

Thanks!
smt

Thanks

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cvairwerks

Well-Known Member
Saw somewhere else an estimated shipping weight for the basic motor of around 175 lbs.

Niels

Well-Known Member
Can it function inverted?

rtfm

Well-Known Member
Look, anything called an eninge can do anything...

Appowner

Active Member
I would venture to say most if not all motorcycle engines would require some form of gear reduction in order to swing a proper prop at a proper RPM.

My 2008 two cylinder EFI HD Motor is some 1850cc (103ci). It produces over 100 hp and 100 ft pounds of torque. It comes on the cams starting at 1800 rpm and continues all the way to 4500 with a 5500 red line. And there are a lot of them out there that are bigger and can do a lot more.

Aviacs

Well-Known Member
Saw somewhere else an estimated shipping weight for the basic motor of around 175 lbs
Thanks - that's a good start. If "shipping weight" includes gearbox, primary, & clutch, the trimmed weight could be interesting, also assuming some of the case could then be cut off with lighter covers cast or milled from blocks, to suit reduced dimensions. Of course adding the coolant system brings the weight back up again.

Can it function inverted?
*Sort of imagine any "aircraft use" and de-rating would include a single carburetor suitable to the purpose.
Funny, all the old Triumphs are dry sump, but i have not read whether these are or not. either way, the oil system would be no more insurmountable than a wet sump VW, Continental, or a dry sump radial.

Any knowlege about 3 cylinder TV vs props or re-drives?
Engine architecture/crank position (compared to VW, say) might even allow belt type.
VW in a fast small airplane almost demands gears to keep the prop centerline within the "natural" streamlining area of the engine shape.

Can't get my head around a V-twin in a fast airplane. Seems like TV would be untenable?
Plus the triple is 40% larger capacity, maybe at the same weight? & smaller frontal area, depending on cooling system design.

*edited: actually, the engine is factory fuel injected, full FADEC, another plus.

smt

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Appowner

Active Member
As for applications, S&S motors in Wisconsin produce after market parts for HD engines and complete HD engine clones. The S&S is considered the go to engine when replacing a failed HD engine.

That said, the British Morgan Motor Company uses the 124 ci S&S engine in their 3 wheel car.

As for the Triumph Rocket, it appears to be an inline water cooled which brings it's own flying issues.

Aviacs

Well-Known Member
As for the Triumph Rocket, it appears to be an inline water cooled
correct.

which brings it's own flying issues
Anyone can allude. What can you elucidate? Regarding this specific engine of course. Not unrelated examples.

That said, the British Morgan Motor Company uses the 124 ci S&S engine in their 3 wheel car.
Also correct.
And before that, JAPrestwich V twins and even Panther motors. In modern times, the occasional Guzzi.
Which/or all of these in your mind would be a good match for a light airplane, 160-ish mph cruise?
What is the weight of the S & S 124?
Do you know of any flying AC installations?

Thanks!

smt

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Aesquire

Well-Known Member
There is? was a belt PRSU & HD-( clone or original ) engine package, don't know current availbility.

My OPINION is that a 45deg. V-twin is a vibrating monster, which would shake a plane to bits, but proper mounting is possible! I base that on my own, 1205 cc Buell ( H-D Sportster w/better heads & much lighter flywheel ) that uses an Erik Buell designed chassis & vibration control system.

Almost Unique today to the H-D line of air cooled 45 deg. V Twins is the "knife & fork" connecting rod setup, that has both cylinders in line, no offset. That means all motion is in one plane. The Buells with those engines have it rubber mounted AND a stressed member of the frame. ( without the infamous Norton Commando handling decay )

So you need to limit motion & let it rock n roll simultaneously. Not easy. Because of the properties of the elastomer, my bike literally dances at idle, with mirrors, fenders, your eyes, all vibrating in different directions. But as rpm increases, gets smoother. Perfectly acceptable at 1800... Like glass at 6000. ( seductive characteristic, eh? )

I see no reason the throb of an inline Triple can't be tamed with rubber motor mounts. You just need to accommodate the physics.

You need a PSRU, though, even with the big torque of these engines, you need to spin them up to 4500+ Rpm to get that 80+ Ponies.

Weight you can get an engine, complete, down to is the current important unknown to me.

pfarber

Well-Known Member
very experimental conversions and not always optimal weight-wise
And that's exactly what this is. A WAG at something that already has been done. The 80-120hp arena is chock full of off the shelf conversions or you could get a o-200 or A-80 and rebuild it for cheap.

Other than a neat one off side project... unless they can get it done for $2k its not much to get excited about. Aviacs Well-Known Member But you didn't answer any of the questions i asked nor the ones i asked you about qualifying your own WAG position? Basically you are trying to redirect my post to talk about your personal qualms, rather than substantive info. 1.) how much does a bare 2450 cc Rocket 3 engine weigh? 2.) has anyone else ever attempted a airplane related conversion? 3.) specifically, what should i know about TV relating to 3 cylinders. I think others have provided enough info for now. unless they can get it done for$2k
& who is this "they" of whom you speak?

Thanks!
smt

pfarber

Well-Known Member
Basically you are trying to redirect my post to talk about your personal qualms, rather than substantive info.

1.) how much does a bare 2450 cc Rocket 3 engine weigh?
2.) has anyone else ever attempted a airplane related conversion?
3.) specifically, what should i know about TV relating to 3 cylinders.

I think others have provided enough info for now.

& who is this "they" of whom you speak?

Thanks!
smt
Maybe too heavy?
Can't find weight with all the non-essentials removed (gear box, etc). Liquid cooled/needs radiator.
Is there a problem with the vibration signature for airplane?
People remember their HS Bonnies oil leaks & Lucas electrics; or thrown rods in the 750 Tridents, and just still don't trust Trumpets???

Tech spec aside, the cost and benefit needs to be well above what is already available. The 80-100hp space is full of engines. Unless you can do it VASTLY cheaper, lighter or offer some benefit not already out there... who cares?

IF you believe the hype, the Liquid Piston engine will simply crush anything in the 80-100hp range.

So other than 'because' what is the engine bringing to the table?

Aesquire

Well-Known Member
Liquid cooled motorcycle engines are better, generally, than air cooled for aircraft conversion because the airflow pattern is very different, often 90° to original.

The gear case and all but the minimum gears for a PSRU are dead weight, and might be difficult to reduce.

See the video above for 3 cylinder vibes. Rocking Crank nose in plane of cylinders.

I'll assume the desired \$2000 is for the PSRU alone. Engine price used is highly variable.

It CAN be done. I don't know if it can be done for close to the same total weight as a Rotax 912.

Aviacs

Well-Known Member
Thanks, Aesquire -