hydraulic Prerotator

bones · 22-09-2006, 07:00 PM

Ok fellas, i've started on my own design of a prerotator, using hydraulic pump and motor up the top with a bendix to drive the rotors.
So the first starting place was to find out the flow of the little pump that i have, having done that now ordering a motor of the reduction that i need for it to happen, thats the easy bit, the hard bit for me was to work out a way of driving the pump, so i starting tinkering with electric clutches, and i think i have found one to do the job, a simple bit of machining to make a bush to connect it all together, a braket and then we're done, the only thing that is in the air is, is the electric clutch up to the job, however after digging around in a auto leccy's yard i found a compressor that had seized, and the belts had worn flat spots on the pulleys til the belts burned off, but the clutch still works, so i'm hoping these little buggas have the grunt to do the job.
So i fitted a rotor tach this arvo, and my electric one gets the blades to 130 at peak revs, so with that in mind, my figures are looking good, if things work out the way they should on paper, i'm hoping to get 275 Rotor RPM at 2500 engine RPM's, then start to throttle on till the gyro gets light on the ground then flatten it, by the time i get 3000 engine RPM the rotors should be somewhere around 320 RRPM, now these figures are one to one,, not allowing for leaking in the pump and motor, so with this in mind, i hope to get to some where over 250 from 2500 engine RPM and over.
It will all depend on the clutch though, if it cant handle the power i will be throwing at it, if not then i guess i'll be looking for some other way to power up the pump, but the clutch appeals to me from a piont of, there is no loose belts flapping around near the prop, as in the slipping style of drives i have seen, every thing is tight, then all is needed to engage things is a little button to feed 12V to the clutch, if at the end of it all it dont work its only gonna cost me a few hundred bucks and quiet a few head aches..
Will keep you all posted and give a few picy's latter on..

Graeme · 22-09-2006, 07:25 PM

Your a good bloke Bones. I just love it when someone else dose all the R&D perfecting a new gizmo.
Being down here in Vic now for a while I don't have access to workshops and experts to play around with new ideas. Keep at it mate and feed us all the good info.

niquenaque · 22-09-2006, 11:29 PM

Quote:

Originally Posted by bones

'

a auto leccy's yard i found a compressor that had seized, and the belts had worn flat spots on the pulleys til the belts burned off, but the clutch still works, so i'm hoping these little buggas have the grunt to do the job.

Must have been an observant driver in that car...

You might try and find out what the torque on that clutch is, 250 RRPM is near to flight speed and will most likely get your machine very light and twitchy on the ground which could be a danger of itself, especially until you get used to it, a gusty day could be very exciting..

The torque value will be important long term as the clutch will slip when powering the rotor at high speeds, if you are not aware of this slippage and it gets hot - red hot in some cases it may seize / weld itself up and lock your rotors into gear with the prerotator, which could be very ugly until you shut the motor down, never mind the fact of red hot metal and oil / petrol being in near proximity to each other. I am aware the bendix should disengage but that is at lower revs, if per chance it is engaged and decides to shit itself when you are half way down the strip at half noise you could have a problem, it may also affect your engine performance adversely. A sprague clutch on the prerotator is recommended, they can be found in auto transmissions if you need one or alternately the NSI redrive gear boxes have them, as do some washing machines.

Another concern would be that the clutch will also 'grab' when engaged and put some shock on the assembly, similar to a starter motor without a soft start. You might consider feeding the voltage in with a variable resistor as well to dampen that issue down, though the bendix may not throw in until a particular number of revs is reached.

Don't let this deter you though, just keep it in consideration while you are building the prerotator.

Cheers,

Nick.

bones · 23-09-2006, 08:54 AM

Quote:

Originally Posted by niquenaque

You might try and find out what the torque on that clutch is

Try to find that is like trying to find hens teeth Nic, i rang near every body who would talk to me about these clutches, no one could tell me how much torque they could handle..

Quote:

if you are not aware of this slippage and it gets hot - red hot in some cases it may seize / weld itself up and lock your rotors into gear with the prerotator, which could be very ugly until you shut the motor down, never mind the fact of red hot metal and oil / petrol being in near proximity to each other. I am aware the bendix should disengage but that is at lower revs, if per chance it is engaged and decides to shit itself when you are half way down the strip at half noise you could have a problem, it may also affect your engine performance adversely.

Well damn arent you a cheer up to society then AYYYY, but all things aside Nic, i have never heard of one welding itself together, not saying it not posible, but if its slipping enough to do that i WILL hear it, and i'll know as the motor revs will climb very fast.

Quote:

Another concern would be that the clutch will also 'grab' when engaged and put some shock on the assembly, similar to a starter motor without a soft start. You might consider feeding the voltage in with a variable resistor as well to dampen that issue down, though the bendix may not throw in until a particular number of revs is reached.

Not to worry about that Nic got it sorted out, a very simple and fool proof system in place for that, and with the pump im using the shock if i didnt have a dampening system in place would probably twist off the ring gear, as it is a gear pump, once it starts pumping the oil HAS TO GO SOMEWHERE, and at engage speed that is about 180- 200 RRPM, so something would give..

Quote:

Don't let this deter you though, just keep it in consideration while you are building the prerotator.
Cheers,
Nick.

I'm not NIC, any one got any thoughts on things i may have missed??? one thing for sure is i'll be trying it for the first time without the rotors on just incase i have missed something

nicholasn · 23-09-2006, 09:41 AM

The clutch you are useing sounds like the ones I use at work I put about 20-25 hp on them runing 61" three blade mowing deck. I can stall the engine by loading up the deck, so spining up a pump should be fine you can get ajustable clutch that if they slip you can reset. Once it is spining it should be fine I have had them runing at 4000 rpm with load .

Gyrodes · 23-09-2006, 10:37 AM

Bonesy, For softer start use a bleed tap between the in and out on the pump, which will be closer to the seat than the motor, eg shorter hoseing. When the rotors are stopped engage the clutch with the tap open then close the tap to increase the pressure/ rpm to the system. Most electric clutchs I have observed in operation engage with a servere torque aplication (in short a hell of a bang)

. My concern with out the bypass tap you would be a cork screw mast candidate. Supposed you could sell them to the house decorating industry as modern art

. What hoseing you going to use from the pump to the hydramotor? Ok I only use hydralics all the time so what would I know!

Ya can email me if ya like but make sure you mention prerotor in the subject line as i'm copping a lot of shit mail. Keep up the good work there. Des Garvin

russ · 23-09-2006, 11:17 AM

Quote:

Originally Posted by nicholasn

The clutch you are useing sounds like the ones I use at work I put about 20-25 hp on them runing 61" three blade mowing deck. I can stall the engine by loading up the deck, so spining up a pump should be fine you can get ajustable clutch that if they slip you can reset. Once it is spining it should be fine I have had them runing at 4000 rpm with load .

You have my undevided attention here..............give me more "details"

ie..........brand / type / etc etc

bones · 23-09-2006, 12:17 PM

Its with great sadness that i annouce the death of my project before it even really started,,,,, hmmmm well on to MK.2

Quote:

Originally Posted by russell

Quote:

Originally Posted by nicholasn

The clutch you are useing sounds like the ones I use at work I put about 20-25 hp on them runing 61" three blade mowing deck. I can stall the engine by loading up the deck, so spining up a pump should be fine you can get ajustable clutch that if they slip you can reset. Once it is spining it should be fine I have had them runing at 4000 rpm with load .

You have my undevided attention here..............give me more "details"

ie..........brand / type / etc etc

me too Russ cause the one i just thought was gonna be the one just shat itself in a test that i just done in the shed

,,,
So i need info on a clutch that is light enough, and strong enough,, Please

Quote:

Bonesy, For softer start use a bleed tap between the in and out on the pump, which will be closer to the seat than the motor, eg shorter hoseing. When the rotors are stopped engage the clutch with the tap open then close the tap to increase the pressure/ rpm to the system

That exactely the simple system i was gonna use, that was you can bring in full flow slowly as the rotors pick up,,

The hosing would have to be proppa hyd hosing to take the pressure, the real flex stuff cant think of the name at the moment[/quote]

nicholasn · 23-09-2006, 12:33 PM

Russell give me a call 0414968936 I have in my workshop a have some thing else you mite like
nicholasn

russ · 23-09-2006, 01:48 PM

Sweedish, blonde,blue eyes,25,big tits.............i'm on the next jet