Prerotator help needed

[gyroplanes]

I had a guy contact me that bought a gyro with a homemade prerotator, it is the common style that takes power off a small flywheel on the front of the Subaru (by the mast) via a Wunderlich wheel and bearing housing. It looks like they had a mid-ship bearing of some sort on brackets half way up the mast. It probably used steel square "slipper" tubes from that point up to the Wunderlich head unit.
The guy sent me a very small flex shaft of about 1/8" that fits between the lower unit and the mast brackets. There is no way this tiny flex shaft could transmit any rotational power. The unit was probably never completed. This picture is not from his gyro. I see a U joint on this one, could a slipper shaft extend all the way to the rotorhead or it that too long?

I was figuring that a Wunderlich style flex shaft assy could run from the lower unit, vertically, to the mast bracket where it would transition to a slipper shaft assy.

I hope someone here has a similar set up and could provide some pictures I could show him. Any help would be appreciated.

[Dennis D]

Hi Tom.
Don't know if this is anything close to what you are talking about.

[BUD ONEAL]

Tom,
Mine is built almost as that one. I have a 1/2" square shaft inside a 3/4" square shaft with about 8" or so as a slip point. I have a impact universal joint at each end welded to the square tube. This has served me well for about 15 years.

[dinoa]

Tom,

What you have in the picture was originally made by Ed Alderfer. It is as Bud describes.

Dino

[OuterMarker]

Tom......contact Kevin....he has the Sub setup and alot of photos....

[TansAir]

Hey Tom,

I have the same setup ... Wunderlich wheel and bearing housing at engine, Wunderlich head unit up top (has no junction mid-ship, is a straight shot as you can see in one of the photos I post). Not sure of the dimensions of the channels, but the larger, hollow square channel runs from bottom up (from wheel & bearing housing assembly, attached via uv joint, all the way up). The hollow channel obviously terminates at a distance that will prevent interference with full aft stick). At the head unit, another uv joint with smaller square stock coming down from that (solid stock was used for mine). Not sure of the length, but I believe it's probably around 8" or so. Plenty of length so they don't come apart with full forward stick, and telescopes smoothly in all directions of my jolly stick.

Mine works nice, don't know how long in service though. The wheel is very hard duro ... that could be age or material itself. I thought about going with softer wheel but fear it will twist the uv joints apart (they are a bit sloppy as it is), so a little slip of that wheel is probably a good thing. I'd like to upgrade to the joints Dennis is using at some point though.

Hope this helps,
Kevin.

[Brent_Brown]

I want to use this on my 2.2. what rrpm do you guys see?

[BUD ONEAL]

My drive is a bit differant as we have a flat plate for the lower drive wheel to run on.The plate is about 8" round and is machined to fit into the front engine pully.The rest is much the same.I see right at 200 rrpm.

[bmoore2156]

Tom,
You asked for some help a few months ago about a RAF lower prerotator assy. I now have what you are looking for. Call me 541-272-1000
Brad

[TansAir]

I want to use this on my 2.2. what rrpm do you guys see?

My drive is a bit differant as we have a flat plate for the lower drive wheel to run on.The plate is about 8" round and is machined to fit into the front engine pully.The rest is much the same.I see right at 200 rrpm.

Mine starts to peak at around 100rrpm, with slightly above idle engine. I get impatient at that point, disengage the prerotator and start taxi to spin up from there. FYI: I have the EA-81 engine, the blades are 25FT Rotordyne.

I like the idea of larger disk on pulley wheel face, in combination with new wheel for the bearing housing may be good upgrade for me at some point. I'd like higher rrpm's but for now no complaints.

Hey Bud, can you post a picture of your wheel bearing housing assembly showing your pulley plate/disc and how the bearing housing is mounted? If I upgrade my system, it would be good time for me to clean up that entire area and could use as much inspiration as I can get. Thanks! Kevin

[dinoa]

I used to see 180rpm with 25ft sky wheels off an EA-81.

Dino

[WHY]

Question, would it be better to have the large tube on top and the small tube at the bottom because of moisture that might run down inside the large tube when it is facing up ??? Or does this facilitate oiling or lubing the slip joint ???

Tony

PS Don Graves up in the new england area built something like this only he used a right angle drive at the bottom and a "cone clutch" , he could engage it with one finger on the lever, got well over 200 rpm

[gyroplanes]

Thank you all for the replies. I hope he can rebuild his own prerotator from your photos. I will encourage him to join the forum as well.