Stu's KB2 restore/redesign

[Chopnotch]

So, I know I have a lot to mod on this baby to make it work. I just put the blades on and unless the push tubes limit the aft tilt of the blades, they will interfere with the prop. I'm guessing a drop keel would solve that but, if anyone has any ideas to keep it classic so, it will still fit in my garage, I would like to go that route if possible.

In the previous "Howdy" introduction thread we discussed modifying the location of the engine more aft about 2 inches to make room for the push tubes as they interfere with the fan shroud. Now that these blades have been attached and we have prop clash, moving the engine aft will make that interference worse.

Perhaps a rotor head assembly with a couple inches more height is an option or will that throw CG or operations envelope off too much on this KB2 design?

Thanks for your thoughts!
Stu

http://c4.ac-images.myspacecdn.com/images02/116/l_5d83070d65c340dbaa1f868f84d7bcab.jpg

http://c2.ac-images.myspacecdn.com/images02/125/l_6b21fde0696c4deeaefe996bbc3f37b5.jpg

http://c4.ac-images.myspacecdn.com/images02/117/l_3c5f4f40501444cca15183bd69665edb.jpg

http://c1.ac-images.myspacecdn.com/images02/141/l_45395b6358a34e89a815975ff416a948.jpg

http://c1.ac-images.myspacecdn.com/images02/105/l_324c07237e5849f28e0e9da248950508.jpg

http://c1.ac-images.myspacecdn.com/images02/122/l_2e6cbf66717f43fd95d4ae6256535530.jpg

[Chopnotch]

Pics are of the bad set of blades. Pulling out the good set for cleaning and pics in a little while.

[dabkb2]

You can check out how Billy got around his motor on this thread http://www.rotaryforum.com/forum/showthread.php?t=22627

[Chopnotch]

Thanks again Dave! Your avatar pics are the stuff! Very cool.

Here are more pics... the second set of rotors. I can't identify either set personally. These are in good shape except for a dent/crack which might make them junk now. If you guys know the under structure of these things, maybe you know if they will work as is or can be repaired. Looks to just be skin of one rotor by the mounting plates with the rest blemish free.

http://c4.ac-images.myspacecdn.com/images02/119/l_ab549b7a31d64f59aacea3716fcaec8f.jpg

http://c4.ac-images.myspacecdn.com/images02/124/l_0330b543964b45cca250f50ee254857b.jpg

http://c3.ac-images.myspacecdn.com/images02/118/l_f7a8664da83e48fb97fcf30c1bbe2ba6.jpg

http://c3.ac-images.myspacecdn.com/images02/148/l_540a78b4471c441286953bc69e7836b6.jpg

http://c3.ac-images.myspacecdn.com/images02/139/l_dccd654055f842ebb4cce3f85495d516.jpg

Those rusty mounting plates look real nice don't they? (jokes)

[Chopnotch]

Are these Rotordyne blades?

[Timchick]

How large is your prop? The original KB/Bensen frame was designed to use a prop with a maximum size of 52". On the direct drive Mac engine that size worked fine. With a Rotax it's usually too small and people use around 60" and up. If you do this on a KB-2 there isn't enough space between the keel and the rotor blades. That's where a drop keel mod comes into play. It adds more clearance between the keel and rotor blades without raising the thrust line up too high.

[Chopnotch]

The prop is a 52" Tim. Tennessee Prop.

So, I have mismatched parts... engine to frame... prop to engine... Maybe the Rotordyne blades will work but the Bensons are just for show and maybe groundwork.

Hmmm... I wish I could go VW since I know VW... I really need to figure out a way to keep it under a standard garage door height else, figure out a way to do the drop keel with a disconnect to slide it under the door. Still trying to maintain Part 103. Whoohoo! Looking like an impossible wish list to hack through while still keeping in mind I am a large framed dude and may be pushing the limits of this design in the first place. Waiting for the pic of the gas tank bung to hit my inbox from phone and I will post the pic in the tank thread.

Any ideas?

[giro5]

Do a double hang test on it and see where the cg is with you in the seat relative to the center line of the prop right now. You will be much better off with a good rotax than the vw due to its weight. http://www.rotaryforum.com/forum/showthread.php?t=25222&highlight=double+hang+test Here is an explaniation of the double hang test:

Why not start a solid works drawing of it now as is.

Looking at your next to last pic close up I would not do anything with those blades. Rust, other corrision and a hole or tear.

[Timchick]

If you're redrive gear ratio is 2:1 then a 52" prop will work with that engine but I don't think it will have enough power to fly you very good. I had a 52" prop on a dual carb 503 on my KB-2 and it did OK with me but I weigh 160 lbs and fly at sea level.

I was looking your photos compared to mine and it looks like your mast may be shorter then it's suppose to be. Look at my photo. The top of my prop tip is around the bottom of the rotor head cheek plates. The top of your prop looks higher than that. That's why there's not enough clearance between the prop and the rotor blades.

I believe Rick Martin weighed about the same as you when he had his gyrobee. If you went with a BB with a dual carb 503 I think it would work for you.

[giro5]

Also looking at the teeter towers and hub bar the pic does not seem to show much teeter movement available. Any one else want to comment on this?

[Des Garvin]

Chopnotch, In your third pic your control cross arm appears to be held in place with white cable ties and not the 2 bolts in the torque tube on the rotor head, if this is so you are not going to get the true prop verses rotor clearence. Just an observation I have observed.
Look forward to you answer. Cheers Des Garvin, from downunder. Yeh you blokes up over recon we Aussies see things upside down. :lol::yo: Des

[Chopnotch]

Thanks for the pic Tim! Cool machine! I think it may be an illusion on the pic. Check out the reduction setup on my engine. It's a belt drive and it's dropped several inches below where your prop mounts so the thrust line looks close to the same but my engine mount is mounted higher on the mast. I guesstimate 4-6 inches. Will verify tomorrow when I a back out there. I will also take a measurement from the floor to the top of the head to cross check the height. Maybe the solution is to change my reduction drive method to your style allowing the engine to be mounted lower? That seems like it may save a drop keel if it works. If the mast height is the same, I should lose the interference (rotor to prop) and lower the cg if that is better.

It also looks like your engine is mounted a little further aft from my present location. I have to wrestle the plastic cooling fan shroud to remove it as it does clash with the mast in removing it. Looks like there is enough room on yours to remove it with no problem. I don't like the rear engine support struts on this one as the band saw cut a little bit into the mounting plate... Looked like a stress failure point t me so, while I am at replacing those, it won't be a big deal to make a new horizontal engine support strut to move the engine back two inches which in combination with lowering the engine, should free up my push tubes to return to their proper location. I think that might work... what do you think? What kind of reduction drive do you have? Do you know or was it on your engine when you bought it?

I'll do a rough check on the head tomorrow Giro. Dan flipped me the specs so I can check if it's all in tolerance and built to print.

[Chopnotch]

Chopnotch, In your third pic your control cross arm appears to be held in place with white cable ties and not the 2 bolts in the torque tube on the rotor head, if this is so you are not going to get the true prop verses rotor clearence. Just an observation I have observed.
Look forward to you answer. Cheers Des Garvin, from downunder. Yeh you blokes up over recon we Aussies see things upside down. :lol::yo: Des

Thanks Des! Yea, with the engine mounted where it is and the proper cheek plates, way too much interference to get the control arm located to position. It is also missing the upper trim spring plate so, i will need to make one when things start to fit proper. Today is day 7 of my ownership of this machine... fun working out the issues with you guys! I think the problems are starting to sort themselves out. At least the major mechanical ones.

Thanks for the input!
Stu

[Chopnotch]

Mast height 72" floor to teeter bolt c/l.

Engine output shaft to reduction drive gear c/l to c/l - 6" drop so if my prop is close to the same location as yours (it appears to be visually), my engine is mounted around 1/2 ft higher.

[Flying_Lab_Rat]

Thanks again Dave! Your avatar pics are the stuff! Very cool.

Here are more pics... the second set of rotors. I can't identify either set personally. These are in good shape except for a dent/crack which might make them junk now. If you guys know the under structure of these things, maybe you know if they will work as is or can be repaired. Looks to just be skin of one rotor by the mounting plates with the rest blemish free.

http://c4.ac-images.myspacecdn.com/images02/119/l_ab549b7a31d64f59aacea3716fcaec8f.jpg

http://c4.ac-images.myspacecdn.com/images02/124/l_0330b543964b45cca250f50ee254857b.jpg

http://c3.ac-images.myspacecdn.com/images02/118/l_f7a8664da83e48fb97fcf30c1bbe2ba6.jpg

http://c3.ac-images.myspacecdn.com/images02/148/l_540a78b4471c441286953bc69e7836b6.jpg

http://c3.ac-images.myspacecdn.com/images02/139/l_dccd654055f842ebb4cce3f85495d516.jpg

Those rusty mounting plates look real nice don't they? (jokes)

I think those could be repaired...anyone with some even mediocre skills with a TIG welder could probably get that sealed up no prob. As it's close to the blade roots, the balance shouldn't be affected enough to warrant thought.

[Timchick]

My rotax had a B-box with 2:1 gears for the short prop. Even if you get the prop/rotor clearance sorted out I doubt your engine with a 52" prop is going to have enough power to fly you at your weight.

[Chopnotch]

So, how can I sort this out? I have interference with prop and rotors. Adding a little height with new cheek plates seems the way to go from previous advice. I either have to move my engine more aft which will cause more problems with the prop as the rotors tilt back so much and adding a larger prop magnifies this problem. So, how much height can I add safely with cheek plates? 4-6 inches? I really want a tame machine to start out with... if I get airborne and can fly a few hundred feet off the ground with no stunt man maneuvers, I will be cool with that for now. If I add rotor height I will need to construct new push tubes for height and possibly with 2 bends to clear the engine. I am not sure if T6 tube will bend without stress fracture but, I am not experienced with tube bending. Any advice?

[dabkb2]

Do not bend the push rod tubes. There is a hing mechanism that will allow the push rods to clear the motor. I will try and find a pic.

[Chopnotch]

Hey Dave, was it like the setup on this bird?

http://www.rotaryforum.com/forum/attachment.php?attachmentid=69749&d=1274402760

Anyone have some good pics of this push tube setup?

[dabkb2]

That is the setup, I still can't find any pics

[Brent_Brown]

I would make your gyro look just like this green one.

[WHY]

There are some other benefits from this arrangement, by putting the "walking beam" in the middle you also dissrupt a lot of the harmonic resonance that the long tubes are subject to. Over time this kind of reaonance can fracture rod end bearing at the thead or literally beat light bearings out of the socket.

Look closely at some videos the next time a good close shot shows up in some videos or even look at your own in flight (if you can) and notice the "dance" or even just hold one of them while doing a run up and FEEL the vibes , not good.

Tony

PS another point to consider, is SINGLE BEARING tail mounts, do the same thing on these have someone help you (to be safe) and have them do a run up while you hold the tip of the rudder and you will probably feel several different reaonance vibes as the engine goes thrugh it's rpms. You will never get a chance to see a "crack" here, the vibes just work harden the metal over time until it breaks like a piece of glass.

Back in the early days of Mentone I had the good fortune to see a EARLY model RAF with the single post rudder do a high speed fly-by over the runway and the rudder looked like it was mounted on a jack hammer (another good reason to attend the major flyins).

[Friendly]

Hey Dave, was it like the setup on this bird?
Anyone have some good pics of this push tube setup?

The set up you see was changed to this style of idle arms. They give more freedom of movement while still capturing the 1/bolt on both sides. It can be made with a drill press, band-saw and good file or belt sander.

The material is IN wide x 1/2 thick x 5 in long 6061 t6 alum. Drill out the holes and band-saw the straight cuts and sand, file or what ever means you have to clean up the saw marks. Then drill the 1/4 holes in the width for the attachment bolts. This just a suggestion. :yo:
Hope it helps

PS, remember to shave the end of the fork that is attached to the tube so your clamps are secure to the mast and allows free movement of the fork.

[WHY]

Hey Mark

Really a great set up and good design on those idler arms, would make one comment for your consideration,------the top rudder suport from the mast to the rudder where it transitions from round tubes (which are good) to a flat material and goes about maybe 4 to 6 inches back to the rudder. that sharp bend at the transistion point is a real "stress riser"

Tony

[Friendly]

Tony,
Thanks for the input. It is not apparent in the photo. where the angle flat plate is located, there is a another plate about 1/4 in inward that is Tig welded to the other plate. In other words it is double plated. If I did more KB 4s I would make a jig and dress that up some. I had a friend suggest I make it more 3 dimensional for the same reason as you suggested. I am make a few improvements on this gyros prerotor system, so when I am sure that is where the tail strut will be, I will address that bracket.
Thanks for the input as always.

[Chopnotch]

Thanks a million for the pics Mark. That makes sense. You did a nice job on 'em!

I am thinking I'll probably go drop keel then. Is 6 inches typical? I'm guessing there isn't a standard for hacking one of these up with all of the important dimensions for CG and all already worked out as that would be my weak point without modeling it in CAD.

Stu

[Friendly]

Thanks a million for the pics Mark. That makes sense. You did a nice job on 'em!

I am thinking I'll probably go drop keel then. Is 6 inches typical? I'm guessing there isn't a standard for hacking one of these up with all of the important dimensions for CG and all already worked out as that would be my weak point without modeling it in CAD.

Stu

Stu,
Its not hard, just takes a little time. Did you read the thread on Drop Keel KB3?
I will be happy to help you where I can. My email is mcarmouche2@bellsouth.net