Electric Pre-Rotator

@All_In Any more news on your project you mentioned in October ?

phil
 
Sounds good guys waiting to hear all the results, I used to have a mechanical flex shaft 300rpm pre rotator but now just getting back into gyro's and needing a new set up electric is just easy. And any electric that will do near 200 static will be very effective if left on during the take off roll accelerating the blades rapidly from there.

wolfy
 
jm-urbani said:
the RC command brushless controllers can be controlled by a pod ( a sevo tester)
I will put the servo tester on a lever with a micro switch under so that I need to push on the pod to power it
the controller does not send current to the brushless until you turn back the pod to zero ( to avoid any brutal start)
the controller also has a soft start
plus I will install a timer relay that will send the current from the pack to the controller only for 2 minutes

so to pre-spin i will have to

- place stick fully ahead
- pull back the rotax throttle to idle ( coz I will use the left hand to control the pre-spinn process)
- push the timer relay button still with left hand
- push the pod down, zero the pod, and then turn it smoothly ( it as 300° from 0 to 100%) to increase rpm applying the wheel brakes at the same time ( the lever is on the stick)
- as soon as I get 140 rpm stick back fully
- finish the pre-spin
- realease the pod and the brakes and full throttle

in fligth the timer will cut the current so that there zero chance for the pre spinner to start while flying

I don't want an automatic system for the moment ...
Click to expand...


I very much admire your efforts concerning the electric pre-rotator. I often wonder if i could be possible to (somehow) integrate the electric pre-rotation motor in the rotor axle, with co-axial induction coils, hence eliminating all moving parts...
 
XXavier said:
I often wonder if i could be possible to (somehow) integrate the electric pre-rotation motor in the rotor axle, with co-axial induction coils, hence eliminating all moving parts...
Click to expand...
YES !! When time and money permit, there are some new outrunner motors that provide much torque and it is my plan to put one around the rotor head for testing. I know, Chuck, we don't want to add more weight up there. ;)
 
XXavier said:
I very much admire your efforts concerning the electric pre-rotator. I often wonder if i could be possible to (somehow) integrate the electric pre-rotation motor in the rotor axle, with co-axial induction coils, hence eliminating all moving parts...
Click to expand...
It has been done, that German manufacturer (gyro tech I think ) were building there gyro's with that style of spinner but they seem to have disappeared. I think there later models they went back to a more conventional engine driven system for some reason.

wolfy
 
jm-urbani said:
Hi,
I think that the manufacturers have no interest in developing an electric pre-spinner when you know that existing systems just work good
home builder are the only one that are crazy enough to design and machine such a system.
however it is nice to try , the benefits can be interesting, for me the more important is to get rig of any mechanical link btw the rotor head and the gyro frame, secondly I am totally tiered of occuping the runway 4 minutes on average before taking off, thirdly I hate the feeling of mechanical where the brakes and the rest of the pechanical parts are under pressure the propeller pushing the gyro , with all the vibrations and so on , all of this is not satisfactory for me etcetc...
Click to expand...
Yes I totally agree with you, I definately don't like having a sliding spline etc joining the head to the mast.
And yes I used to have an engine driven 300rpm spinner that worked very well but with the rotax doing about 4200-4500 rpm the brakes are the limiting factor. To be able to do electric that gets near 200 static would be good enough for me. My mechanical spinner couldn't be left on during the roll because the engine didn't have any more power while driving the prop. Electric is independent and from 200 while rolling will accelerate rapidly.

wolfy
 
wolfy said:
Electric is independent and from 200 while rolling will accelerate rapidly.
Click to expand...
If 200 rpm of the electric spinner seems sufficient to you, why do not they seem sufficient to you with the mechanical spinner, since then the thrust of the propeller and the gripp of the wheels discharged by the rotor, do not yet create problem ?
200 rpm instead of 300rpm requires only 44% of braking, while the grip of the tires increases by 50%
 
Last edited:
Jean Claude said:
Required power varies with (diameter)^4
So, talking about rrpm prerotator, without specifying the diameter makes little sense.

For only 1.5 kw mechanical produced by a car starter you need 3 kw electrical.
This electric power requires:
ordinary car battery: 30 lbs
Odissey 625 15 lbs
Lithium 3 lbs
Click to expand...

Why not use the 3 LB. battery on board for electrics and jump the solenoid to the starter with the car battery on the ground. Then disconnect the cables. Is it really necessary to carry a high amperage battery?
 
Jean Claude said:
If 200 rpm of the electric spinner seems sufficient to you, why do not they seem sufficient to you with the mechanical spinner, since then the thrust of the propeller and the gripp of the wheels discharged by the rotor, do not yet create problem ?
200 rpm instead of 300rpm requires only 44% of braking, while the grip of the tires increases by 50%
Click to expand...
With electric once at 200r rpm the engine can be advanced almost instantly to full power to accelerate instantly.
With the mechanical (flex shaft) you could not advance the throttle quickly. The quickly advanced throttle try's to advance the rotor quickly but it just sounded bad trying to put that sort of torque through a little flex cable and Bendix. So to advance the throttle slowly to increase from say 200 to 300 with brakes released just eats up runway with out achieving much. Ideally I think the flex shaft style should have an overload clutch at the engine end so it holds up to a constant torque on the flex shaft that will spin the rotors to say 300, after that rpm the engine can be advanced but the clutch will slip allowing the engine to advance.
Electric is just simple (which I like) but I doubt it will ever be as good as a 300rrpm mechanical, with a 300 rpm mechanical just release spinner and go.
Type "wolfie showing his agile gyro" into youtube the first take off was about 300 rpm.

wolfy
 
You are right Wolfy. I love Birdy's technique where he keeps the pre-rotator engaged during the t/o roll. I do it regularly with the AR1. Of course, there is a lot of torque reaction in the process. But the results are amazing. Unfortunately, that is difficult to do with an electric spinner.
 
thomasant said:
You are right Wolfy. I love Birdy's technique where he keeps the pre-rotator engaged during the t/o roll. I do it regularly with the AR1. Of course, there is a lot of torque reaction in the process. But the results are amazing. Unfortunately, that is difficult to do with an electric spinner.
Click to expand...
For the reasons stated in my last post I think it's easier to do with electric rather than mechanical, unless there is a overload clutch for the mechanical.
What sort of spinner does the AR1 have?

wolfy
 
Not an engineer so be gentle. I suspect that the problem is the initial torque required to start the rotor turning. How about a CVT
 
wolfy said:
For the reasons stated in my last post I think it's easier to do with electric rather than mechanical, unless there is a overload clutch for the mechanical.
What sort of spinner does the AR1 have?

wolfy
Click to expand...
AR1 has a mechanical one.
 
PRA hopes to test ours soon and will let you know.
 
The G-Impact fuel cutoff switch we are testing with all testing successful so far.

The prerotator is about to be tested at full speed for the first time.

The jump take-off has been scaled back to developing only a power take-off as they could not finish all the machining of the swashplate and controls in one semester. Next year's class will add full jump components and improve it if necessary but will know the RRPM speed needed of 500 RRPMs at zero pitch and what it will do as a predator with fix pitch for now. Just going to shim it to zero pitch for testing the same blades.

They are also building a Yamaha 80HP engine as a test platform for the jump take-off in a modified KB2.
Those all have to be finished by June to graduate.
 
The good news is the jump-takeoff team has designed all the components. Only the machine class professor told them no way students can machine, assemble, test, make changes and final test in only 6 months.

Dick Degraw helped and the engineering students spend 3 mounts before final design evaluating electric, hydraulic, and back to power takeoff considering cost and weight to performance with data that show it all for anyone to follow!
 
A note on cheap batteries. I'm building them myself.
I buy used laptop battery packs and break them open and remove the batteries they cost about a dollar each, not $5 to $10 for the best new ones. Many still maintain full capacity and voltage of 4.2 volts.
All you have to do is charge them all up and measure the voltage they hold.
Just make all the batteries are the SAME voltage in each BATTERY and any cheap $3 controller will charge the entire pack but not uneven voltage the excess available in all other individual batteries will only charge to the lowest voltage battery.
The photo is how I test them before I solder the real one together forever. This one cost less than $45.
This kit lets you build a temp battery for testing in minutes using nuts and bolts.
This one has forty 4.1-volt batteries it will be 16 volts and 1/2 of a 32-volt battery pack consisting of two of these in parallel. Each with its own charge controller.

After testing I solder house AC wire striping it first and fold it in half to the exact length I need. Then clamp it in a vice and twist it into one thicker wire. If you don't have a spot welder use a VERY BIG and HOT soldering iron tin the wire first.
Then you connect them in series with a thin wire that will blow like a fuse if over the max amps any one cell should be drawing if not defective. Like Tesla does.
Then just a fraction of heat on the battery on the thin wire linking all cells in series and parallel
Note: Heat can destroy batteries. They can explode with a small low temp iron as it will take so long to transfer the heat.

Here is the quick build kit for testing. https://vruzend.com/ Although people do use them in production. It cost more than house wire.
BatteryPack.jpg
 
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