Gear reduction vs belt reduction

[lanichol]

After a post I read recently, I am a little concerned about the belt drive stripping on a AAI modified RAF. I believe the person was careful in his inspection, but the belt stripped suddenly.

How many hours before the belts should be replaced?

Can anyone tell me gear reductions that would work on the RAF?

Thank you in advance.

[WHY]

Hi Larry

I don't know for sure about Neil Hintz unit, but I got to see it up close at Mentone when he gave his seminar at the convention a few years back and it was a work of art and the quality was outstanding. He may have a set up for the 2.2 or the 2.5 by now. I'd give him a e-mail and see. Sorry I don't the address but I think it is some where on the forum.

Tony

[banaari]

http://www.autoflight.co.nz/

[GyroRon]

There is nothing wrong with the belt system. If you change it to a gearbox you will have major work to do to come up with a way of running the pre rotator unit. You need to INSPECT the belt often and it helps to run 2 or 3 narrow belts at the same time instead of just one wide belt, this way if a belt goes the other may allow you to make it back to the airport without a loss of power.

[lanichol]

There is nothing wrong with the belt system. If you change it to a gearbox you will have major work to do to come up with a way of running the pre rotator unit. You need to INSPECT the belt often and it helps to run 2 or 3 narrow belts at the same time instead of just one wide belt, this way if a belt goes the other may allow you to make it back to the airport without a loss of power.

Ron,

This is new to me, but probably a discussion that has been hashed before.

I like your suggestion of having more than one belt that could act as a backup. Are there people running more than one belt on a RAF, SparrowHawk, or AAI modified RAF?

Thanks

[GyroRon]

I had three narrow belts on my RFI redrive on a gyro I used to own. Contact Don Parham about it and he can help you with this.

[ultracruiser41]

Speaking of drives...Ron, what is the ratio on your Dominator?


BarryK

[GyroRon]

2.67 to 1. You want to spin these little props as fast as you can....

[Aussie_Paul]

2.67 to 1. You want to spin these little props as fast as you can....

I think you have a 582? What is the prop diameter Ron?

Aussie Paul. :)

[GyroRon]

582 with 60 inch prop Paul. Gear box had 3 to 1 gears when I got it, changed them out for the 2.62 or 2.67 - can't remember which they are off hand. If I had a B box instead of the C box I could have gone with a set to spin the prop even faster.

[Aussie_Paul]

Thanks Ron, yes that makes sense. A 60" with the 2.62 C box sound great.

I think the niose level would start to be a problem if you spun it any faster!! Noise means less efficiency.

Aussie Paul. :)

[KenSandyEggo]

The pulleys have to be aligned and the belt must be run "banjo-string" tight. The Gates GT2 belt is about the best I know of. Keep the belt very tight, make sure it is not rubbing against a flange and use a GT2. You should experience no more problems. The pulleys are aligned on the RAF by adjusting the 2 top brace bars that are over the engine from front to back. (Mast cross-bar to top of the reduction unit).

[lanichol]

The pulleys have to be aligned and the belt must be run "banjo-string" tight. The Gates GT2 belt is about the best I know of. Keep the belt very tight, make sure it is not rubbing against a flange and use a GT2. You should experience no more problems. The pulleys are aligned on the RAF by adjusting the 2 top brace bars that are over the engine from front to back. (Mast cross-bar to top of the reduction unit).

Thanks Ken,

[Screw]

Screw-In

Yeah, but check out his performance!

Screw-Out

[GyroRon]

Screw I love those pictures!!! Wish someone had a video of us coming through that gap in the trees!

[Timchick]

Hopefully next year you will.

[Gyro-Cop]

Tim,
think you might get Ron on tape going through the bean pach, I think that would sure be something to see. That is if you could get him to repeat the action that took place.

Charlie Graham
Northport, AL

[Timchick]

I'm sure if I'm around enough with a camera I'm bound to get something on tape. I'm looking forward to seeing a flyby of several gyros with the smoke going.

[Mike Schallmann]

Having built and flown several redrives I think the belt drive is a good way to go--however I have seen several redrives with stripped belts but this is not a design fault it is a setup issue. Without exception all of the failures that I have seen were due to the belt being setup to loose. In every single case the owner of the redrive felt that the factory (or belt manufacturers recommendation) was "too tight". Properly set up abelt redrive is virtually trouble free.
Im also NOT a fan of multiple cog belts-If they are ABSOLUTELY not IDENTICLE one belt will carry more of the load and will be subject to early failure and this failure could result in the jamming of the other belt.
I have RFI Redrive #1 on my gyro and it has performed flawlessly for well over 400 hrs. I changed the belt at 250 hrs --it looked perfect and dimensionally wise it was exactly the same as the new one -I keep it as a spare --but I'll probably never need it --I wont change the belt I have on it now until I get 500 hrs (on the belt)

[CypherNinja]

Thats true about manufacturing tolerances in the belt lengths. Just about the only way to eliminate that is to use seperate belt tensioners on each belt.

[lanichol]

Having built and flown several redrives I think the belt drive is a good way to go--however I have seen several redrives with stripped belts but this is not a design fault it is a setup issue. Without exception all of the failures that I have seen were due to the belt being setup to loose. In every single case the owner of the redrive felt that the factory (or belt manufacturers recommendation) was "too tight". Properly set up abelt redrive is virtually trouble free.
Im also NOT a fan of multiple cog belts-If they are ABSOLUTELY not IDENTICLE one belt will carry more of the load and will be subject to early failure and this failure could result in the jamming of the other belt.
I have RFI Redrive #1 on my gyro and it has performed flawlessly for well over 400 hrs. I changed the belt at 250 hrs --it looked perfect and dimensionally wise it was exactly the same as the new one -I keep it as a spare --but I'll probably never need it --I wont change the belt I have on it now until I get 500 hrs (on the belt)

Mike,

That is a good expansion on what Ken J said earlier. What about that much side torque on the bearings? Probably the reason for the bearing mod suggested for the RAFs. I assume you check the bearings when you replace the belt. How do you identify a problem bearing? Noise, tight, ect.?

Thank you.

[pbradley]

I fly on a EA81 in front of a 1.89:1 Amax reduction drive with a toothed belt, as distinct from a ribbed belt. Max Peeters, the aussi manufacturer, states to set the belt up with some slack, which gets taken up when the drive heats up during operation. I stick to that instruction and have done 300 plus hours on the current belt with no sign of wear. The feeling is that properly maintained it could last 1000 hours. I know that Max sold quite a few of these drives in the US, and would be interested to hear what sort of run others are getting out of their units and belts.

[Neil Hintz]

Autoflight gear reduction drives do not apply bending to the engine crankshaft. The input gear on the Autoflight gearbox is supported on its own bearings with a rubber connection to the engine. Car engine crankshafts were never made to handle side load as many belt drive units apply. Two factors to think about, the crank is bending slightly every turn and the main bearing at the flywheel end of the engine gets a hard time wear wise, sending metal to the bigend nearest and eventually lack of oil supply as the clearance gets too big, well actually a diminished supply. I have seen this first hand on many occasions, thats why I designed the Autoflight gearbox the way I have.

[Neil Hintz]

WWW.autoflight.co.nz

[Heather Poe]

Ron,
This is new to me, but probably a discussion that has been hashed before.


See: http://www.rotaryforum.com/forum/showthread.php?t=4593, post #15

[lanichol]

Autoflight gear reduction drives do not apply bending to the engine crankshaft. The input gear on the Autoflight gearbox is supported on its own bearings with a rubber connection to the engine. Car engine crankshafts were never made to handle side load as many belt drive units apply. Two factors to think about, the crank is bending slightly every turn and the main bearing at the flywheel end of the engine gets a hard time wear wise, sending metal to the bigend nearest and eventually lack of oil supply as the clearance gets too big, well actually a diminished supply. I have seen this first hand on many occasions, thats why I designed the Autoflight gearbox the way I have.

Neil,

I see you have a gear reduction for most of the Subs

[Designed for use on Subaru EJ 2.0, 2.2, 2.5, EG 3.3 & EZ 3.0 (H6) engines ]

Compared to the RAF or AAI modified RAF belt system, where does the prop line up? Do you have a pic of an install, including the alternator.

I am suprise someone has not built a redrive that includes a hydraulic pump that could be used for a pre-rotator. Of course you open a whole door of possible problems.


I also noticed you had a link to sub4 with a 4 port E81 heads
for dual spark plugs.
http://www.sub4.co.nz/

Do they build a similar head for the EJ 2.0, 2.2 ect.?

[Neil Hintz]

17330Larry, offset on the Autoflight gearbox is 79mm, this can be in the offset up from the crank or the offset down possition. My gyros use a prerotator drive from the opposite end of the engine to the gear reduction unit, aulternator drive end, this goes through a small angle drive then through a shaft drive to the rotorhead. Preasantly use a polly vee belt with a tensioner but next gyro onwards will be using the new cone clutch system ( in oil ). I don't know much about SUB4 now, I've not been involved with them for several years now. Here is a picture of an offset up version on an EJ 2.0