Pre-rotator ideas...need help

magilla

Gyro Project Owner
Joined
Dec 17, 2005
Messages
546
Location
Little Rock, AR
Aircraft
UH-1H / UH-60A
Total Flight Time
2000+ RW
OK, it's been 4 years since I've had the Jungle Gym in my garage, and I'm finally in a place where I can work on it and get it going.

I've completed the new 2276 motor, with 84" prop, and I have a new double-bearing rotor head installed. Everything is there for it to fly...except the pre-rotator.

I have two hydraulic pumps (Griesen 25's), I just have to figure out how to drive them.

After nearly a year of trying to mount it to the driveshaft end of the VW (the pulley end has the 2:1 Valley Engineering redrive and prop), it got WAYYYYY too complicated.

(I had an electric mower clutch mounted to a driveshaft mounted to the hydraulic pump)

Just too many issues. It became a nightmare...

Then one day, when I separated the motor from the Diehl accessory case, I had a brilliant flash (I think)

Tell me whether you think this would work:

If I cut a small ellipse into the top of the Diehl accessory case where it mounts to the engine, I can expose a portion of the flywheel.

The VW flywheel has a 1" essentially flat section before the ring with the starter teeth.

If I use a small rubber friction wheel, (like those used on the direct drive pre-rotator systems), and mount directly to one of the hydro pumps, I could mount a plate for the pump to rotate and have the wheel engage the flat spot.

I know they make X-shaped Diehl accessory cases with flywheels exposed, so I am not worried about strength issues with the ellipse cut out of the Diehl case. The pump will rotate down via cable, and the wheel will engage the flat spot behind the teeth. The pump will be mounted to a plate attached to the frame, so no weight or stress will be felt by the Diehl case or the motor mounts...

The flywheel is fairly large, so to maintain a decent ratio for the pump, the wheel dimaeter will have to be 5" or so.

Anybody see any problems so far?

On the driveend, the griesen pump is attached to a bendix, which then engages the 89-tooth wheel on the rotor.

I would prefer to mount it directly with a freewheel clutch system...removing the bendix and ring, and putting a belt on. The rotor would always be able to go faster than the pre-rotator, when engaged.

What do you think?

Need some help with parts, if they are available - like a pulley for the RFD head, and a line on freewheel clutches

Otherwise, I need to mount an electric pre-rotator. It's an RFD head, but I can't seem to find any RFD electric prerotators or systems.

Any help would be appreciated. If I don't get this thing off the ground this next year, it's going to be sold.
 
Sounds A.O.K

Sounds A.O.K

Visual looks ok to me.

Sounds like a good work around, but the driven pulley may need to be larger than 5". If the width of the drive area is at least 3/4" wide it should work, on paper of course, real world could work out differently.

However an electric pre rotator is the easy way to go. Best bang for the buck.

Jonathan
 
HI Spencer

Sorry but I think I gotta rain on your parade, the hydrualic drive is so "positive" that the friction drive will not be able to transfer the power without slipping.:(

Tony
 
Spencer,

For our tandem trainer we used an electric clutch off of the sepentine belt to drive the hydraulic pump. One for an A.C. system would work.

Jon
 
Are you driving it like a drum setup (Mac) or plate setup (ultrawhite)? I personally belived it will be turning awful fast, but maybe not. I use a 12 in drum on my Rotax and it works well in the drum fashion.
 
Hi Spencer

Are you driving a mag off the flywheel end ?? Does the engine have dual ignition ??

Tony
 
Electric pre rotator dude....... told you this years ago. You'd be flying the thing if you would listen.

Your going to have to fabricate a bracket off the torque tube to hold the starter motor. Ultracruiser put one on his snowbird, maybe he could send you pictures of how he mounted his starter.

The rest is just running wires to the battery and a switch on the dash. Simple, easy and effective.
 
OK then. I have resigned myself to an electric starter motor redrive.

I have an 89 tooth wheel on the RFD double bearing head.

Does anyone have plans or sketches for an electric prerotator for an RFD head??

Especially the torque tube mount and type of starter motor?

Any 2-phase systems out there?

Anyone have a torque tube for an electric pre-rotator?

Will a dry cell 12v battery work? Or do I need to get a bigger battery?

I am frustrated...sorry...I just want to get this thing rolling, and I am fresh out of ideas.
 
How far are you from Ron Herron? Surely he could scratch up something for you. Elsewise contact Ultracruiser41 here off the forum.
 
Good suggestion Mike!

Good suggestion Mike!

Or contact Nicolas Karaolides, Aviomania here on the Forum. He has a lightweight electric prerotator system.

http://www.aviomania.com/products.htm

Good suggestion Mike.

I held that prerotator in my hand and it was very nicely made and seemed light.

It was almost enough to make me want to abandon my hydraulic prerotator scheme on Mariah Gale.

The Toyota starter on the Predator is one of my least favorite features.

It is heavy at eight pounds plus several pounds of wire.

It stops the radio from working so I can’t line up and wait with the rotor turning.

I seldom see the other side of 100 rpm static with my 30 foot Sport Copter blades.

I broke two of them in 700 hours of flying.

The hydraulic scheme is heavier still but should address the other two challenges.

It is complicated and untidy.

Thank you, Vance
 
Hi Spencer
Great suggestion guys, as the US Agent for Aviomania I too would be glad to help. I love to talk about flying any time.

When it comes to aircraft weight to power ratios = everything!!!

In addition, here is a link to the prices in Dollars.
http://pra31.org/Vendors/AviomaniaInfo.aspx

Just put in a exchange 'Rate' of $1.36 = today's rate and you can see the cost in dollars.

PS:
There is an even lighter more powerful version with and including a RRPM display 'To be tested and then announced soon'!

Here are some pictures:
 

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Why don't you post some detailed pictures so we can get an idea of what you have and maybe offer some other suggestions, after all the gyro originally had a hydraulic prerotator both when it had direct then reduction drive.

.
 
The gyro originally had a VERY unique friction-driven hydraulic drive that was set up through the redrive on Joe Terminella's machine. The driveshaft went through the center of the prop hub...

I bought the gyro without the engine (and without unique redrive)

I installed a Valley Engineering VW with redrive, and top-mount carb/intake that precludes the use of the original system. I also do not have the capability to machine a 1/2" hole through the center of a 1" bolt.

Let me dig up some pics and I'll post in a minute.

I sent emails to Ron Herron, Joe Terminella, Nikolas K, and Ultracruiser41, and RFD to see what they had as far as electric pre-rotators.
 
Pics of original and new engines

Pics of original and new engines

Here are some pics
 

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Hi Spencer

I was thinking about the pre-rotor Jim Eich used on his JE-2 and it got me to thinking about a "hybrid" set up. Jim mounted a "chainsaw engine in his pylon and said it worked quite well. I notice you also have a pylon (sort of) but was thinking about using a short telescoping shaft arrangement to the bendix and mounting a REAL starter motor in the pylon. the gear reduced starter is for sure the most powerful, but the "little" Toyota starter will amaze you if you take it apart and see the tiny size of the armature that is doing the work to turn the rotor. I'm think maybe something like a starter motor from a older chrysler which is also gear reduced but much larger armature. It sure is a problem, with the motor on the torque tube you have no torque between the rotor and mast but have the weight of the motor on the rotor head , with the motor on the pylon then you have torque between the rotor and pylon, but I cannot seem to come up with a way to get "power" without weight.

Tony
 
Spencer ,
any flat plate of 6061 x 1/4 will hold your starter to the rotor head. Usually a longer bolt is used through the bearing to sandwich to the torque tube or pitch tube and then another bolt to prevent it from twisting. As Ron said it is simple. I ran a starter attached to my keel for a while (because it is the fastest way to install a prerotor and cheapest I think) but not the best setup. Especially for larger rotors. If you have one of Toms Bendix installed you can run a telescopic shaft from the starter to the Bendix. Electric is quick and easy, but heavy and only good for about 125 to 130 rrpm. That is enough for taxi, just much less than what is available if you tap into the power of the motor. Just my opinion.
 
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It sure is a problem, with the motor on the torque tube you have no torque between the rotor and mast but have the weight of the motor on the rotor head , with the motor on the pylon then you have torque between the rotor and pylon.

Sorry, this is incorrect. Only if you drive the rotor directly such as a shaft going from fuselage straight up to the head like a helicopter will you not have torque on the mast.

.
 
Spencer,

You're need to post bigger pictures of your setup, not very small ones, and especially of the reduction drive.

From what I can see the battery you are using is most likely too small for an electric prerotator but post the battery specs here. For electric you need to think car battery size. Also, what is the charging system output?

.
 
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