# Aeromarine 60hp V-Twin Engine

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#### soupercooper

##### Well-Known Member
HBA Supporter
if you ask me Kevin has been VERY SHARING, so sharing that Aeromarine is running with it, as for Ace Aviation I cant vouch for him, Ive done business with him ONCE and logistics and delivery were bad but quality and price was good. he uses SKF bearings or some sort of german bearing maybe FAG, in my hands their high quality machined parts and nice anodized finish, someone can help maybe by adapting a gear drive to it in mean time all we have is a belt drive so be thankful we at least have that!, the poly-v belt is the widest Ive ever seen and surely can handle the HP. IMO its pretty impressive for a belt drive. I think kevin has at least 30+ hours on the belt drive but he's not good about posting his total hours on his you tube channel, I have asked him to do so but no luck yet. This engine is set up ITS NOT for anything but light LSA or maybe some stout ultralights like my Reliant SX (heavy duty J3 kitten).If I recall the engine use ball bearings on the crankshaft and not the typical sleeve bearings, i need to look into that, I do know its a tapered output shaft.

#### pictsidhe

##### Well-Known Member
I have had brief correspondence both with Kevin in England, and with the Ace Aviation PoC in India. Kevin gave me access to his Dropbox, which has a LOT of detail on his conversions. I haven't dug into it to see if the details of the redrive are there or not. You MIGHT be able to deduce all the relevant masses and spring constants from the detail drawings. I don't think either Kevin nor Ace actually know doodly about torsionals. And even Gates is pretty closed mouth about the stiffness of their sourced components. What I can say is that nothing I've seen about the Ace Redrives indicates that they have any sort of resilient decoupling element that would make them torsionally "soft". If one wanted to design one, say with a "Guibo" like a Rotax E box, I bet Ace would be happy to chew you one out of billet, for little money, decent quality, long lead time, and frustratingly slow, if any, communications.
All I wanted was pulley and belt sizes to make a first approximation of natural frequency. I have enough belt, prop and engine data to work from there. Ace does not know anything about TV, let alone have analysed it.
I eyeballed the drive dimensions from pictures instead, and didn't like the numbers that I got. That took me from probable customer, to likely competitor. I will not be copying the Ace drive, which is what they are worrying about. Ironically, I'm almost certainly going to farm out the machine work if this goes into production, which Ace does seem to do well.

#### Tallyho

##### Member
The gk engine with a redrive for use in drones has been around for a while from a company called subaruair air in china. Only seem to have a presence on alibaba. They use the 1000cc version.

#### Tallyho

##### Member
Will add that Kevin still deserves credit for bringing the smaller engine to a wider audience and his personal testing.

#### soupercooper

##### Well-Known Member
HBA Supporter
The gk engine with a redrive for use in drones has been around for a while from a company called subaruair air in china. Only seem to have a presence on alibaba. They use the 1000cc version.
View attachment 102925
looks heavy and looks really busy? maybe a clutch and other components stacked to it?, anyone else have comments whats all stacked up behind the gear drive?

#### soupercooper

##### Well-Known Member
HBA Supporter
800 Aircraft

this is Gaokin web page on there Aero version
though this link is not the engine we were discusing it just does have me curious, this gaokin engine is 2-stroke 100hp at 800cc at 77 pounds, water cooled EFI as well.

#### erkki67

##### Well-Known Member
I’ve always admired this reduction drive, it’s a tooth belt of Otto Funk and his company flyeco .

id like to see a similar PSRU on the GK engine Kevin is using.

one thing for sure, this block requires a fair additional amount of machining compaired to the Ace redrive.

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#### erkki67

##### Well-Known Member

its just for the reduction drive unit, not for the engine

#### Tallyho

##### Member
looks heavy and looks really busy? maybe a clutch and other components stacked to it?, anyone else have comments whats all stacked up behind the gear drive?
72kg and 90hp. Seem to gave a selection of redrive available. I have no idea what is in the housings. Plus it's rotax money before shipping a duties.

#### sharpvector

##### Member
The gk engine with a redrive for use in drones has been around for a while from a company called subaruair air in china. Only seem to have a presence on alibaba. They use the 1000cc version.
View attachment 102925
Not cheap at $15-20K #### Bill-Higdon ##### Well-Known Member The gk engine with a redrive for use in drones has been around for a while from a company called subaruair air in china. Only seem to have a presence on alibaba. They use the 1000cc version. View attachment 102925 Subaruair was on thise website for a while, #### soupercooper ##### Well-Known Member HBA Supporter Not cheap at$15-20K

no that price is a complete package as seen in photo, stand alone redrives i found are $1500 to$2000 range. but i got a reply from them saying "currently not available" i responded to ask when they are available, i think they are the middle man and I will try to find direct source, maybe its Subaruair but like a previous post subaruair not to be found lately. i have photos of stand alone gear and belt redrives from alibaba source of price range of $1500 to$2000 from 4 different models. i read its china mfg. but German engineering. attached is one of four varieties of stand alone redrive at $1500 to$2000 range, these will be ALOT easier to import than engines! been there done that, dealing with EPA is the killer when importing engines! they mentioned they can make adapters for other engines, there is not much out there for prop redrives besides of course rotax. and a couple others like the one for inline 4 piston yamaha engine from I forget the name right now.

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#### soupercooper

##### Well-Known Member
HBA Supporter
I’ve always admired this reduction drive, it’s a tooth belt of Otto Funk and his company flyeco .

id like to see a similar PSRU on the GK engine Kevin is using.

one thing for sure, this block requires a fair additional amount of machining compared to the Ace redrive.
that is called a cog belt and more for timing functions or applications, i believe poly-v design is better fit in our application as you want a little bit of give or slip for TV issues or vibration or prop strike etc etc? i could be wrong and IM sure someone will chime in on this statement if Im wrong.

#### rv7charlie

##### Well-Known Member
I suspect that the engineers will disagree with that a bit. Unless you're talking about something like a CVT belt, slippage isn't a good thing. Even Valley Engineering, using a multi-V belt, didn't depend on belt slippage (which would quickly burn the belt). They used a spring loaded idler, very similar in concept to what you see with automotive engines' accessory drive belts. As I understand it, the TV goes into the idler's spring, rather than slipping the belt.

I could be wrong...

#### pictsidhe

##### Well-Known Member
I suspect that the engineers will disagree with that a bit. Unless you're talking about something like a CVT belt, slippage isn't a good thing. Even Valley Engineering, using a multi-V belt, didn't depend on belt slippage (which would quickly burn the belt). They used a spring loaded idler, very similar in concept to what you see with automotive engines' accessory drive belts. As I understand it, the TV goes into the idler's spring, rather than slipping the belt.

I could be wrong...
Yes, you are!
The valley engineering idler works like a one way clutch. Once belt tension exceeds a certain level, it springs in and let's one side of the belt go slack. The belt then slips a bit. Managing TV is tricky. The system needs the natural frequency out of the useable speed range. If oscillations do build up, they can very easily reach the point that something breaks. Slippage is one way to deal with that. If you don't have a 'slippable' connection somewhere, you have to be really, really careful. Many if not most amateur sized systems are 'soft' natural frequency is below idle. But a misfire at idle or even accelerating during startup can put the drive into the danger zone. Slip of something is one way to deal with that for short periods.

#### rv7charlie

##### Well-Known Member
Valley Engineering - Big Twin
Look at rotation direction, and tensioner location.

My undestanding is that there's a difference between a 'compliant' torsional frequency changer ('absorber') and a slipping belt. One should prevent the other (along with other, worse things).

#### rv7charlie

##### Well-Known Member
But slip isn't required to change tv freq.

#### pictsidhe

##### Well-Known Member
But slip isn't required to change tv freq.
No, but it adds enough damping to stop it. Try it at high power, you will smoke your slip device. Just ask Bede. Elsewhere, it is extremely useful for those annoying points you need to run through, but don't really want a honking big device to move it away.
The Valley tensioner limits negative torque during TV events. The numbers for my own redrive suggest I need a stiff tensioner on the drive side to reduce the natural frequency and a soft 'Valley' tensioner on the slack side to damp out TV at low RPM. Like Valley, I will thoroughly test it myself. IR temperature guns offer an easy way to check how much energy the belt is absorbing.

#### BBerson

##### Light Plane Philosopher
HBA Supporter
The Valley Engineering drive had about six hard rubber balls in ports that functioned as a one way device, not belt slip.