2.62:1 Rotax "C" gear box, or the gears

[Chuck Irby]

55 teeth on the large gear, and 21 teeth on the small gear is what I am looking for.

[GyroRon]

Chuck why do you want this gear set? And I am not trying to be a smartass. Just wondering.

[Chuck Irby]

Ron, I now have a 3:1 gear ratio. What I really need is a 2:1 with this small prop. A 4 blade prop would work also. But I can't get the hub I would need in a 4 blade. I am having to run 18 degrees of pitch now and I still need to add pitch to attain my desired max rpm, which is 6500 or slightly less. As you know, a faster prop speed would require less pitch.

Ron, you did tell us that you're running 87 octane gas in everything, right? I just started using 87 also. It was 1.59 here yesterday.

[scottessex]

Hey Chuck, Call CPS and see if they have any used gears in thier repair dept.

Do you think my 2:0-1 will work with my new engine and 60" prop?
I was running a 2:73-1 on the Arrow, at about 10 deg pitch. That sounds kind of weak doesn't it.

[GyroRon]

Chuck okay then, that is what I thought. I have been chasing that same gear set for a month - I have a ad for them on Barnstormers - Yes the 3 to 1 ratio is too high I believe for a 60 inch warp drive and we end up with way too much pitch in the prop. Spin the prop faster means less pitch. Of course it takes more power just to spin the prop faster so who knows if it will result in us having more thrust - cause thrust is what we want!...

I have gotten a call Thursday from a Farmer in MINN. that has a set of 2.62 to 1 gears with 50 hours on them and he is going to send them to me to try out. He wants a set of 3 to 1 or higher gears as a spare set for his T bird. If I like them I am going to send him my 3 to 1 gears and were even. If I don't like the 2.62 to 1 gears then if you still want a set I will let you know.

I am a little concerned about going to a 2.62 to 1. I know the engine and gearbox and prop are all smooth with the 3 to 1. I have heard stories that using the wrong ratio will end up giving you nasty harmonics and tear things up. I wonder if anyone here has experience with the 2.62 to 1???

I also bought a Clutch for my C box. I bought it off Ebay earlier this week and the seller happened to live only a few miles from Todd Powell our Forum owner, Todd picked up the clutch for me and shipped it to me on Thursday. Thanks Todd!

Scott, I think the 2 to 1 ratio will be okay. But it will be loud!!! If your turning 6000 engine RPm the prop is turning 3000, and that is like a direct drive Subaru.... LOUD!!! I think you might want to do the math on that, I wonder how close to SuperSonic your prop tips will be at 6500 engine rpm. You do not want to go supersonic...

[Chuck Irby]

Scott, I just did the math and at 6500 rpm and the 2:1 ratio, your tip speed would be okay (580 mph).

Ron, that's a good idea to see if we can find someone who has run, or is running, the 2.62:1 ratio. I don't see, logically, how it could be a problem. But what do I know, Huh?

I wish I could get 2:1 gears for the "C" box, but as far as I know, the tallest gears they offer is the 2.62:1

Scott, thanx for the tip re CPS.

PS, Ron, I don't think a gear ratio change will cause us to loose or gain any significant amount of thrust.

I don't think it'll take any more power to turn the prop faster, due to it requiring less pitch.

[GyroRon]

2.62 is the lowest or tallest or whatever you call it we can use with our gearboxes Chucky.

Don't know or understand all the dynamics behind the harmonics - I am just a SLM, simple lawn mower - but I do know that some people have had nasty harmonics on there planes and just by unbolting the prop and turning it on the shaft one hole and re bolting it up a big improvment was made. Maybe this would be a good topic for Chuck Beaty and Doug and the rest of the brainheads. It goes way over my head.....

[GyroRon]

Chuck if we aren't going to get a reasonable boost in trust then why in the heck go to all this trouble? If you are just looking for something to do to your gyro then might I suggest this..... WASH IT!!!

[Chuck Irby]

Ron, while you were posting your last two posts, I was adding a PS to my post #6. So go back and read it again, please.

To answer your last post, it looks like I'll have to go to 19 degrees of pitch to get the engine rpm down to where I want it at WOT. That is just too much pitch for that prop, IMO.

Yeah, you're right. I'll try to fly it in the rain again to get it looking better.

[GyroRon]

Well I expect to see at least 25 pounds more thrust out of this. you think we will get no gain. Why?

[Chuck Irby]

Ron, there you go again rewording what I said. I said "no significant amount".

I am happy with the thrust that I have now, and I suppose that is the reason I even mentioned the thrust gain. My goal is to get my cruise rpm down as low as possible. If I was concerned about getting altitude faster, then I would want more thrust. I normally take off and climb out at 6000 rpm, and sometimes as low as 5500, and rarely ever over 6300. So I have plenty of power for my weight, even with 12 gallons of fuel.

In reality, I know that if you turn the prop faster and therefore use less pitch you will increase the thrust. I am in complete agreement with you on that, Sir Ron of the C's.

It's just that That ain't my goal. I have a tractor to pull stumps with.

[Friendly]

Ron, I was in Mississippi today and what Chuck is trying to tell you is , if you ain't crusin, your just going up and down. I started to check in on Chuck but I went north and south , not to the east of Jackson. I could have welded a couple of extra teeth on that small gear and brought that ratio to a more respectible cruisin configeration.
Chuck , that rain is on the way, she otta be nice and shinny for Bastrop, huh??

[Chuck Irby]

Mark, while I was flying yesterday, I got into a little shower, but I was 15 miles from the airport. By the time I cruised low over the taxiway to check the wind sock before landing, I had picked up another bunch of those pesky love bugs (sure glad I have a windshield). Maybe I can clean it up a little after I get to Bastrop.

Tell me about this Robert guy from down South. Is he from around Houma?