Electric Pre-Rotator

Thats me in the photo with Carl Schneider Dar. I suggested he use the Amp Flow motor because when I was in Battlebots years ago, it was highly regarded for being well made, powerful and relatively bulletproof. At that time it was known as the Magmotor, they changed the name to AmpFlow later. The Carlinator didn't always have an electric prerotator. Carl used the hydraulic pumps built into the HKS motor to run a hydraulic prerotator for some time. I tried that as well, but I was never satisfied with the power output or the weight. I switched to electric and after Carl saw mine, he asked for help choosing components for his. Carls gyro was sold and I'm not sure if the new owner is flying it or not. I believe Carl got somewhere around 165 honest, consistant RRPM. Like fuel burn and climb rate, people often fluff their numbers so comparisons aren't always easy.
 
Not only COVID ,but the tariffs, and now, Hong Kong may lose its most favored trading status since china is taking the country over. I think buying from an American company is likely to be a better experience. Which Kelly controller did you order, the 48 volt 200 amp KDS mini? I believe at that time I would probably have recommended a 4QD controller from England or the IFI Thor spin controller. They were also battle tested too. I'm not sure what Carl ended up with. I would probably suggest the Kelly now though I haven't actually used it myself yet.
 
My sympathies.

My own less than happy effort with the ‘world’s lightest electric pre-rotator’ left a serious dent in my wallet at a time it really didn’t need that.
 
I have a question. Interest is still strong with this one....

What model is the Kelly Controller?

Cheers,

Dave
 
I for one am still very interested in your progress.
I will be shortly looking into electric power once my new gyro is built.

wolfy
 
Wow, you rock! I wrote most of the page for Open Source Project last night. It will have the current status and a donation page.

It needs its own revenue source to be self-sustaining as it's a 5K sponsorship fee that the 1st 3 projects waved they wanted the projects but we have to pay for parts.

So my new thinking is:
We will sell the SolidWorks plans and CNC code etc "For Educational Purposes Only" assuring our team and PRA has no liability.
We will pay S.D.U. back for our 1st project out this revenue, the car-starter project, that is in testing, earns for itself.
But the pricing will be based on the complexity of the and number of components/drawings, CNC or software code.
From $50 to $250 for the Jump-takeoff plans being the most complex, with PRA members benefit of 50% off.
Might aks for a DONATION but as a pre-pay purchase = when it is finished it would be free to those you pay in advance,
Let people vote for the project they want with their wallets to help fund it at first to make it happen sooner rather than later.


I need to get this new source of revenue voted on by the board before I post much more and it may change...
so what happened with this project?
 
The college shut down in March and maybe in the fall the project will pick up again.
 
Yes Dar, you've gone all stealthy on us.... What's up?
 
For 150rrpm static and disc flat I have used an uprated 1.4kw high torque starter motor, the torque is huge, so much so that I have created a three stage "soft start" to ease the RRPM upwards. I researched "aircommandpilot" Bobbys soft start sytem to add an extra torque range, works like a treat, thanks to Bobbys advice and help. Cost was £262 UK sterling. They have other car starter motors up to 2kw high torque.
 
I am still deciding which way to go regarding a pre spinner, engine driven or not.
All these experiments with brushless really has my attention.

wolfy
 
@wolfy mine is not brushless, it started off as a 0.9kw Opel Corsa starter. I then contacted https://www.autoelectricsupplies.co.uk/category/138 for a high torque replacement. £262 for a 1.4kw high torque direct replacement and I have 150rrpm disc flat no wind.

They have high torque starters up to 2kw.

In their info they explain that their starters use less power and produce more torque.

No need for battery cells etc as it runs directly off the engine battery.

IMG_1229.JPG

Sorry for the rubbish diagram, the (V) between relay 1 and relay 2 is A 30A Schottky barrier rectifier (diode) to stop both relays firing when I only want one to fire. The winding bypass on the solenoids is 3.16mm brasing wire with the flux scraped off of the outside, as suggested by Bobby, @AirCommandPilot.


phil
 
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Thanks Jetlag, I have also used car starter pre spinners before.
Without doubt one of the simplest/easiest and probably cheapest options around.
But unfortunately not powerful enough for my current needs.
150rpm that your getting is respectable from a starter, what size rotor out of interest?

wolfy
 
@wolfy rotor are resin 8.3 metres

phil
 
What RRPM are you looking for Wolfy? What size blades do you have? How many prerotations do you need on a charge? is it important to be able to spin the blades up from a dead stop or can you give them a flip in the right direction? How do you want to control the ramp up, directly with a knob or slider or via buttons?
 
Hi jean Michel, hope you are well, the company that supplied my high torque starter at 1.4kw also do them up to 2kw, not sure how much more rrpm the extra 0.6kw would give, but, also it depends on the weight and diameter of the rotor, as you know.
 
What RRPM are you looking for Wolfy? What size blades do you have? How many prerotations do you need on a charge? is it important to be able to spin the blades up from a dead stop or can you give them a flip in the right direction? How do you want to control the ramp up, directly with a knob or slider or via buttons?
Gday John, 28' rotors hoping for 220+ if going electric. 5+ prerotations would be good. It is no problem to give the blades a flick before getting in. Something like the way you have controlled yours would be nice, my original thoughts were three buttons off/reset-slow ramp to 100rpm (for taxiing over rough ground)-full power, all within reach of the throttle so that once the roll has started the prerotator could be stopped at any time during the roll. For fun flying on board charging probably not necessary, but flying for work would require on board charging.
Probably asking a lot.
I just bought a new start battery a Lithiumax 300CCA 13 volt that only weighs 800 grams, could possibly be used in series but charged in parallel.
I am watching a few brushless setups at the moment and waiting on testing.
Or I will go again engine driven but with a torque limiting slip clutch, as to be able to go WOT with prespinner still engaged during the roll.

wolfy
 
it is a petty that they did not reply me when I have asked them the continuous max discharge rate
the details are mentionning a pulse max discharge of 400 Amp for 3 seconds (5200W) per battery but only for 3 seconds ( the time it takes for starting an engine)
I find this solution really expensive compared to RC command lipos of 60 C
Yeah that's a shame JM I thought they might have been more helpful.
Yes I agree it's probably not the best solution, but the attraction for me was the fact that on board charging is built in to the battery.
But probably still better going RC with the BMS you mentioned.

Cheers
 
Then, I will be able to program an automatic acceleration, very smooth at the beginning of my tests checking the Amps figures during the process ( with a CC sensor probe that one can find for a few bucks on the internet)
To obtain a constant current throughout the pre-launch , the programmed rpm must be according to a law depending on the inertia and dimensions of the blades.
To avoid this it is easier, by programming, to enslave the rpm control with the CC sensor you have.

The curve below shows a typical rotor acceleration under constant torque (i.e. with a constant current in the pre-rotator).
Sans titre.png
 
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