[COLOR="Blue"]Question: How long is the longest time period that you run your prerotator for before it pops the Bendix or you release it.

We need to know the battery capacity/life how minuets do you run a prerotator now to take off.[/COLOR]

I need this for:
PRA Open Source Project is well on it way to developing a light weight electric state-of-the-art prerotator!
http://www.pra.org/forums/forumdisplay.php?71-Pre-rotator-Public-sugestions-amp-questions

Our goals:

Push one button forget about it. Unless you flip the emergency shut-down switch or you turn it over near or on the ground; then it turns itself off, and the electrical and fuel system off on blade IMPACT.

Our goal is to rotate 30 foot blades to 200 RRM's then release the brakes while it still driving it during the flapping stage. If you drive it then; the blades will not flap ever? This safety feature is a bonus as you keep driving it up to 350 rotor RPM's for the shortest take-off we believe. Until testing is done we will not really know.

John, I don't think having a stay on switch is a good idea for an electric prerotator, I think a moment switch is heaps better, for a couple of reasons..... eventually the rotors will go faster than the prerotator so a bendix will drop out and happily spin in its withdrawn position, whereas a starter with a solenoid bendix wont, so the gear will stay engaged which could risk burning out the drive pinion clutch, chattering on the ring gear and generally being a nucence.... plus, some people will always forget to switch them off.... I just see it as a very bad idea. I would go as far as saying have 2 moment switches in series, say one on the side of the throttle and one on the joystick, so pressing one accidently (instead of the radio, for example) wont throw the starter bendix in unexpectedly.... imagine if someone was flying along and went to make a radio call and hit the prerotator button by mistake.... the gears crunch and snaps off the bendix that falls off and goes into the prop ..... no, I reckon if you are lining up, you will have one hand on the throttle and one on the stick, so put a moment switch on both so both have to be pressed simultaneously....

Also, people need to get it in their heads that for many years, no one had prerotators at all.... we all flew.... so what is a prerotator for? In my opinion (and I am not talking about 'colossus class' gyros, I am talking homebuilt and open/semi cabined stick frames) is that today, a prerotator is necessary because we now mingle much more with spam cans in circuits.... when a Cessna (spam can) is on final and sees 'another aircraft' on HIS/HER runway..... they expect it to line up and give it heaps and take off.... so they might hold back waiting.... waiting.... waiting..... and if the gyro pilot is a hand spinner trying to nurse the blades up, they get the shits because they have to go around..... or land over the top of the slow gyro.... whose blades are now just coming up and he is about to go balls to the wall..... that situation is not good.... so, In my opinion, we stick people need a reliable electric prerotator that can spin the rotors to just over the hump.... say 100 rpm.... because anyone who cant get any rotors up to flying speed in very short time from 100-120rpm needs to take a look at themselves

Another reason I don't like lock on (cable/hydraulic) prerotators, is if it has a failure and needs to be switched off/unlocked instantly.... if one has to reach for a switch or button to turn it off, it may be too late.... whereas if one is pushing the 2 moment switches or pulling the lever on the stick, one can instantly let it go....

I would like to hear others opinions on the stay on switch VS the moment switch (or 2 moment switches)

Thank you Buddy!!

There are some wise advise here I can use....

This helps!!!

The problem in not making it automatic with a push button switch is the Eurotubs teach to never release the brakes while you are prerotating solely because of pilot work-load!
The Bendix would be a problem if we were not using a micro control unit 'MCU' (it's a micro computer).

Because we are the instance there is no load on the Bendix it shuts itself off. Exactly as Nicolas's does!
That part is so easy with a computer looking at 50,000 time a second and it will know way before any human could. In this case if if left it in human hands and they were slow or forgot human could do the damage you are talking about.

The reason the Nicolas is not pushing his is the Human has to turn the power up with a rheostat and they have burned up 3 out of many!

PRA must keep the human out of it completely!! Bad slow humans!

No worries John, just putting my views forward.... even tho I am actually quite shy (and modest)

I am THAT age, where I am perfectly able to get along with PC's, but just not too keen on everything being computerised and wanting everything done for me... I like to push the clutch on a stick shift car, I like to actually drive it and feel the road and what the car is doing, I like to pat the blades a couple of times then push a couple of buttons to start the prerotator.... I like to prerotate with the stick back so the wind and the prerotator work together...... I reckon the less computers the better.... I like to keep it simple

I can understand simple

I know have a few other friends that feel that way.

I have always been one of the early adapters. Like Standard Oil, the wright brothers, and Apple computers.
I had graduated from high school when the school district bought their first IBM 360 main-frame computer. I begged and pleaded with the school to let me take the first class in summer school ever offered in the USA in 1968. I told them that if they let me learn this now, that like standard oil I recognize that this is the future of accounting system and the first accountant that writes a just a payroll program will be a millionaire. I was right I retired in 1990!

This computer had no monitors or even a keyboard. To boot it you had to flip 8 toggle switches by hand. (8 bit mainframe computer) One line of code at a time and push the next button instead of enter on a keyboard. There were over 400 lines you had to enter just to get it to boot.

Then you fed it a stack of punch cards to enter a program to run. The big improvement was a forty CHARACTER per MINUET printer.

I do not trust humans!!! Computer never fail me because for aviation I use 3 of them and they vote to see if they all agree. If not then it shuts-down the failing chip and uses only double redundancy in a voting pair until you land and replace the busted chip.

Yeah well but humans program computers......
I understand what you are saying john, but over engineering something just because it can be over engineered,
does not make sense to me. I mean early Bensens you just spun the blades by hand.
I don't want to be shackled by battery power or rely on a computer so I can get home.
give me a motorcycle with a kick start!

Seriously the biggest problem is that as gyros evolved they grew taller masts, so hand starting is not an option,
I like your idea, except trying to take the human element out of the equation is counter to what gyros are all about, they are a motorcycle with a kick start, raw basic wind in your face fun, the lighter the better.
I like the idea of a lightweight prerotator, because at the end of the day, anything not necessary for flight just adds weight and kills performance, battery, electric start, wheels brakes, once you are off the ground all that other stuff is just extra weight and drag.
I think that a guarded switch with a momentary toggle would be just fine, take you finger off the switch and it springs back to OFF, snap the cover down and go fly. No micro switches or computer pilot checkers, just simple.

Just my $0.02.

Well we aim to please and it is Open Source to all PRA members...

So we can add you a switch and probably anything else you want. But the controller need a computer to run the motor so you are stuck whit that unless we put a bicycle pedals on it for you... But you are going to be tired and never do even 100 RRPM would be my guess?

Not on mine! I'm way to lazy these days for a kick starter, but I want one as a backup...

It all good anyway you want!

Rather than reinventing the wheel, why don't you take what is proven and improve it?
The wunderlick bendix is proven simple and light, since you want to go electric, why don't you mount the electric motor on the backside of the mast, and use a small driveshaft to the bendix?
Kind of like Jakes Go ped prerotator only with an electric motor.


That way you are not hanging the motor on the rotor head.. Just food for thought.

The reason is the feedback from members. They want it on direct drive to the ring gear.
However we intend to make retro-fits for wunderlick all the rest. If a PRA member wants a one-off we will make that version too. Demand dictated the one we are creating first. I can put the motor anywhere and easily adapt it to all the other versions. The most costly part would be the gear box for a one-off I suspect.

I know your are right Jake!

I can do the MCU programming and I can read and build a schematic!
I cannot guarantee it will work with the team I have now as I cannot do what you make look so easy.
If I had you on the team I would guarantee it would work as the first one would be whatever you said and we would just follow your orders!!!

But I'm going to try my best. That is the only guarantee with everything I do from the group insurance to marketing the airport camping. Throw enough spit balls and at least one to of them will make you rich.

We did just design the gearbox this morning, who knows if that will work. None of us have much experience.

I like simple ! Put a lot of thought in to what I was going to use for a pre-rotator decided to use a simple dependable starter
and a toggle switch . If you forget to turn it off it will just run your battery down... works great ! everything in this pic,is about 10 Lbs.

Well said Jake.... I was trying to think how to best say that but you put it perfectly

If everyone said to car manufacturers that they wanted square wheels for a change.... doesn't mean any manufacturers will try to make square wheels..... they will stay with what they know works..... if they come across something innovative and new.... they will make it and then convince you that you need it.... the following year, all of the manufacturers will all have it and claim they were first to 'invent' it that's just how it works