# High power high speed 90 degree angles sources..?

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#### DangerZone

##### Well-Known Member
HBA Supporter
Are there any new technology high power high speed 90 degree angles available cheaper than the standard helicopter ones..?

I'm looking for the cheapest and lightest 90 degree angle available to buy which could transfer approximately 200HP of power to a prop hub at around 3000+ rpm. Used outboard marine prop angles or bike shaft drive angles would be an option too but it is questionable if they would endure prolonged high power high speed of a variable pitch propeller or be light enough for aircraft use. Another option would be to find some junkyard helicopter tail hub angles, but the high power ones tend to be either slightly heavier than needed or have a turbine attached to it.

Any ideas?

#### Blue Chips

##### Well-Known Member
DZ,
No (normal) helicopter is transfering anywhere near that much HP through a tail rotor.

I would be looking for a rear end to modify, about any of them will do that easilly.

Ken

#### BoKu

##### Pundit
HBA Supporter
You basically have two options: heavy or expensive. Choose wisely.

Thanks, Bob K.

#### DangerZone

##### Well-Known Member
HBA Supporter
DZ,
No (normal) helicopter is transfering anywhere near that much HP through a tail rotor.

I would be looking for a rear end to modify, about any of them will do that easilly.

Ken
True, that's why I asked on this forum, maybe someone has a good idea with minimal (or none) modifications needed.

You basically have two options: heavy or expensive. Choose wisely.

Thanks, Bob K.
There's a third option, cheap and light but time consuming. Time is money, so it might come to the latter one you mentioned in the end.

#### Blue Chips

DZ,
You have one option, a rear end, any off the shelf 90deg gear box to handle 200hp would cost $10K (best guess) and likely weigh about the same as the HP haha Many of these now are of aluminum so relatively light weight. Aluminum race rear ends are also available. Have no idea what you are planning so can't add much beyond the idea of a rear end. #### BBerson ##### Light Plane Philosopher HBA Supporter If piston powered, then you have torsional vibration. Most (others have slip clutch or something) piston helicopters have a v belt drive from the engine. A long v belt can twist to 90°. The 200 horsepower Schweizer/ Hughes has four V belts, I think. #### DangerZone ##### Well-Known Member HBA Supporter DZ, You have one option, a rear end, any off the shelf 90deg gear box to handle 200hp would cost$10K (best guess) and likely weigh about the same as the HP haha
Many of these now are of aluminum so relatively light weight.
Aluminum race rear ends are also available.

Have no idea what you are planning so can't add much beyond the idea of a rear end.
What kind of rear end did you have in mind..? The $10K seems a bit pricey since one can buy a used FJR 1300 rear shaft drive differential for a couple hundred. It is only [email protected] proven but that seems like quite a value difference... The weight of two of these would not be more than 20kg, just to have a reference what can be bought weight/power/rpm/cost wise. If piston powered, then you have torsional vibration. Most (others have slip clutch or something) piston helicopters have a v belt drive from the engine. A long v belt can twist to 90°. The 200 horsepower Schweizer/ Hughes has four V belts, I think. I've seen some ultralight helicopters with 160HP to 250HP with gears and shafts for the main rotor. However, there was no chance to take a peek into the system and the cost would probably be irrational for a homebuilt project. #### Blue Chips ##### Well-Known Member As far as which rear end I'd choose Ford or Chevrolet, lots of gearing options with them. Exactly which one I couldn't say, would be your choice after looking into it. That$10k was just a guess not a price, never priced one, but I can tell you this, it will be industrial, meaning big, heavy, expensive and not at all suitable for anything in a EAB aircraft.

You mentioned driving a prop but what is the end use exactly?
While we are guessing it would would be best if it was at least and educated guess.

I've considered the motorcycle drive years ago for use as a tail rotor gear box but you have no option for needed gear reduction to match your required input/output rpm. Guess there are most always options but not simple ones.

[email protected], that just doesn't sound right, lets say it is, what is the out put RPM? not likely going to be the 3000 you need.

#### Jay Kempf

What kind of rear end did you have in mind..? The $10K seems a bit pricey since one can buy a used FJR 1300 rear shaft drive differential for a couple hundred. It is only [email protected] proven but that seems like quite a value difference... View attachment 37694 The weight of two of these would not be more than 20kg, just to have a reference what can be bought weight/power/rpm/cost wise. That's a pretty out of the box idea. #### DangerZone ##### Well-Known Member HBA Supporter As far as which rear end I'd choose Ford or Chevrolet, lots of gearing options with them. Exactly which one I couldn't say, would be your choice after looking into it. That$10k was just a guess not a price, never priced one, but I can tell you this, it will be industrial, meaning big, heavy, expensive and not at all suitable for anything in a EAB aircraft.

You mentioned driving a prop but what is the end use exactly?
While we are guessing it would would be best if it was at least and educated guess.

I've considered the motorcycle drive years ago for use as a tail rotor gear box but you have no option for needed gear reduction to match your required input/output rpm. Guess there are most always options but not simple ones.

[email protected], that just doesn't sound right, lets say it is, what is the out put RPM? not likely going to be the 3000 you need.
Automobile rear ends would be too massive which means their own mass would create a problem at higher rpm. It is questionable if these rear ends would reach speeds of over 2000rpm without major problems due to inertia and vibrations. Most faster cars (like formula) have lighter moving parts to avoid these problems so I guess that Ford and Chevrolet rear ends would bend, twist and twich uncontrollably at required speeds and break much sooner than some lighter parts.

A well tuned FJR engine produces slightly more than 150HP at the engine crankshaft and a bit less at the wheel. At top speed (252km/h) the rear wheel axle turns at around 2200rpm and the engine over 8000rpm. This is with an aftermarket exhaust, air filter, some tuning but without a turbo. Bikers rarely turbocharge shaft driven bikes not because of the shafts but becuase the gearboxes are usually the weak link and fail when powered over 200HP amd ridden aggressively. The chain has shown to be lighter, cheaper and more resistant to constant accelerate-deccelerate abuse.

The end use is to mount a propfan which should produce a certain amount of thrust, obviously. However, the 2200 rpm of such a motorcycle rear end at top speed is not enough for the propfan diameter, it should be able to withstand at least 3000rpm continuously. The Kawasaki GTR has a shaft drive which can endure top speeds of around 2500rpm but is heavier and without testing of used ones it is impossible to know if it would be any better than the FJR ones. I am certain these shaft differentials would endure the 3000rpm needed but wear could not be anticipated without tests of trial and error. Thus - the cheaper the better, there is no other way to tell.

That's a pretty out of the box idea.
There are others yet their mass is problematic. There are some larger helicopter tail rotor 90 degree angles yet these are either the same or higher mass, or the rpm isn't adequate, or the torque/power is insufficient. The best way would be to design and machine the whole assembly but that would cost more than a homebuilder's budget.

If there are other ideas, please feel welcome to contribute.

#### Victor Bravo

##### Well-Known Member
HBA Supporter
You could make a 90 degree gearbox using some kind of existing industrial gears housed in your own simple box. That would probably reduce the price. This of course falls under 'substituting time for money' as mentioned by another poster.

A company called Kal-Gard (now KG Coatings) makes a molybdenum based bake-on coating that can POSSIBLY increase the amount of power that a given set of gears can take, by way of reducing friction and heat. This coating has been used in high performance automotive applications with some success.

#### DangerZone

##### Well-Known Member
HBA Supporter
You could make a 90 degree gearbox using some kind of existing industrial gears housed in your own simple box. That would probably reduce the price. This of course falls under 'substituting time for money' as mentioned by another poster.

A company called Kal-Gard (now KG Coatings) makes a molybdenum based bake-on coating that can POSSIBLY increase the amount of power that a given set of gears can take, by way of reducing friction and heat. This coating has been used in high performance automotive applications with some success.
Good idea, bearings should also be changed to obtain better power transmission with less friction so some high tech lubrication would be better than the stock oil. Is this coating for high speed applications (3k+ rpm) or for regular gears and bearings..?

#### dino

##### Well-Known Member
HBA Supporter
Boat drive lower unit

#### Blue Chips

##### Well-Known Member
It would be very interesting to me for you to move forward on the motorcycle rear end but my gut feeing is in the end you are going to experience that it is not even close to a viable solution to run a 200HP engine through it with a big prop with all the axial/radial/thrust/gyroscopic potential forces acting upon it, forces unknown to me but they will be there.

Don't get me wrong, I'd be seriously pleased if it worked out.

#### DangerZone

##### Well-Known Member
HBA Supporter
Boat drive lower unit
I already considered boat outboard L shaft drives, but the outer casings are massive. This would mean only the shaft and gear could be used plus a lot of machining. It also seems the water props spin at lower speeds than air props, do you know of any +150HP spinning at more than 3000 rpm which would be light enough for aircraft use..?

#### DangerZone

##### Well-Known Member
HBA Supporter
It would be very interesting to me for you to move forward on the motorcycle rear end but my gut feeing is in the end you are going to experience that it is not even close to a viable solution to run a 200HP engine through it with a big prop with all the axial/radial/thrust/gyroscopic potential forces acting upon it, forces unknown to me but they will be there.

Don't get me wrong, I'd be seriously pleased if it worked out.
Bear in mind that hard forces acting on the rear end of a high power motorcycle produce more problems than soft air acting on a propeller. I'm not trying to disagree because you are right that all forces have to be taken into consideration, but the strains in motorcycle rear forks or outboard boat drives are sometimes a couple of orders of magnitude compared to aircraft propellers.

#### Blue Chips

##### Well-Known Member
They do have at least three qualities I like for aircraft, quality components, light weight and cheap

#### Jay Kempf

##### Curmudgeon in Training (CIT)
Bear in mind that hard forces acting on the rear end of a high power motorcycle produce more problems than soft air acting on a propeller. I'm not trying to disagree because you are right that all forces have to be taken into consideration, but the strains in motorcycle rear forks or outboard boat drives are sometimes a couple of orders of magnitude compared to aircraft propellers.
I am normally on your side of this argument. The thing that airplanes don't have going for them are short prop blades and anchored in gravity on the surface. That means the degrees of freedom for the analysis are a bit more complicated. I don't think it is a show stopper but long prop blades in air are a way worse scenario for a small bearing on a short shaft than a short radius blade in water. Pulses are however pulses and TV is TV no matter how you slice the drive.

#### DangerZone

##### Well-Known Member
HBA Supporter
I am normally on your side of this argument. The thing that airplanes don't have going for them are short prop blades and anchored in gravity on the surface. That means the degrees of freedom for the analysis are a bit more complicated. I don't think it is a show stopper but long prop blades in air are a way worse scenario for a small bearing on a short shaft than a short radius blade in water. Pulses are however pulses and TV is TV no matter how you slice the drive.
Indeed, yet TVs behave different according to many factors, including fluids (air, water) or solids (steel, aluminum, titanium, wood, CF/GF, etc) in which they happen. A person with practical knowledge would easily be able to resolve TV issues while another might see it as an inavoidable problem.

It is also true most airplanes that people generally talk about don't have short prop blades except a few of Cri cris, Hummelbirds, and other known on the internet. However, short blades are quite common in hovercraft propfans where high static thrust and power is needed. Propfans are also used in channeled aircraft and ducted fans so they are far from inexistent as it might seem on the internet.

The real show stopper in any homebuilt aircraft is the budget. We have to plan everything ahead and calculate the time and costs of a project. If these are within limits, such a project could be built. If not, we can still put it all on paper and wait for some other time in the future when prices go down, parts become readily available or something gets cheaper than it originally was in the first place. That's why the emphasis is on 'cheap', because with sufficient funds it is possible to build a private VTOL spacecraft but the budget of a homebuilder does not allow it.