Electric Pre-Rotator

Skyjinks

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Hello....I am involved in building a tractor gyro looking something like an old Cierva with radial engine. Has anyone eperience of using an electric pre-rotator for 30ft blades using thyristor control for start and speed control? Any information would be useful.
Thanks
Skyjinks
 

Vance

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I use a geared Denso starter off of a Toyota for a pre-rotator on The Predator with her thirty foot eight and a half inch chord Sport Rotors.

I do not have a soft start or a speed control.

Typically I see a little over a hundred rotor rpm in no wind conditions and I have been through four starters in over 2,000 takeoffs.

I recently had the starter rebuilt and am now seeing over a hundred twenty rotor rpm without wind assistance. I don’t know what he did differently and he is rebuilding my spare as I write this.

With a tractor I would be inclined to use something more effective that would produce a higher no wind rotor rpm.
 

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Skyjinks

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Vance,
Thank you for your response. Can you tell me how many kW the starter is rated at.
Thanks
Skyjinks
 

Vance

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I will look at it tomorrow and see if it is rated that way.
 

All_In

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Not sure over 10,000+ logged FW, 260+ ultralights, sailplane, hang-gliders
Hello Charles, PRA (Popular Rotorcraft Association} has open source projects for educational purposed.
For Pre-rotators we have 1 soft start circuit using a car starter that can also be a 48-volt high-speed pre-rotator in our library. Members-only pages but will post here if you wish as we changed the new modern PRA to a tax-deductible, non-profit, charity that supports our community whether you support us or not. We still have valuable member benefits and are adding more all the time.

We also have just finished a new two-speed transmission pre-rotator using a cheap car starter with San Diego University senior students. PRA chapter 31 is testing.
See this link to learn more.... https://www.rotaryforum.com/threads...t-is-done-and-ready-for-more-testing.1144536/

This year we have 5 projects with S.D.S.U., S.D.U, and UCLA has reached out but they are 1.5 hours from San Diego. They would have to come to us for testing.
One of those projects is another prerotator you might want to wait for and S.D.U. will be continuing to improve our first prerotator project this next year.
Projects
1) State of the art high-speed (at least 220 RRM with 30' blades) lightweight prerotator using a brushless motor, lithium batteries, and controller. With all things lightweight and powerful it will be expensive.
2) G'force impact fuel-cut-off-switch.
3) Test-stand to test pre-rotators, drive systems, and different manufacturers rotor-blades with data-logger.
4) Lightweight stop and drop landing gear with anti-tip-over (self-leveling on impact).
5) Jump-take-off system to retrofit the fleet. Adapt a helicopter rotor head add electric drive system for jump-take-off capability.

Now I have 3 colleges fighting over PRA projects. But PRA can only pay for the parts for one project at a time. May ask for donations to run all 5 at all 3 colleges is the only way we could let them all try at the same time.
 
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Jean Claude

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I piloted gliders C800, Bijave, C 310, airplanes Piper J3 , PA 28, Jodel D117, DR 220, Cessna 150, C
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About 500 h (FW + ultra light)
A rotor of 9.35m x 0.2m requires about 80 Nm at 120 rpm. It means 1.1 kw mechanical

Car starters is often able of 2 kw mechanical, but provided you choose a battery able of providing 500 amperes at more 8 volts for a minute at each launch. As show this picture.
Accumulator perhaps too feeble or bad gear ratio
Sans titre.png
 

Smack

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Jean Claude, that is a most-confusing chart to me.
Would you define Nm, Um, Cm, Pm, and i(A) please?
Brian
 

Jean Claude

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I piloted gliders C800, Bijave, C 310, airplanes Piper J3 , PA 28, Jodel D117, DR 220, Cessna 150, C
Total Flight Time
About 500 h (FW + ultra light)
Nm is the rpm (blue scale)
Um is the voltage gived by an car battery of 12volts - 60 A.h (red scale) when the intensity is no null.
Cm is the torque produced (purpel scale)
Pm is the mechanical power produced (green scale)
I is the intensity of electric current asked to battery by the starter

We see mechanical power is maxi (2100 w) when the rpm is 1400 rpm. At this moment, the asked intensité is 500 Ampères and the battery voltage is only 8 volts (in other words 500A * 8v = 4000 w electrical )
 
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All_In

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Not sure over 10,000+ logged FW, 260+ ultralights, sailplane, hang-gliders
A rotor of 9.35m x 0.2m requires about 80 Nm at 120 rpm. It means 1.1 kw mechanical

Car starters is often able of 2 kw mechanical, but provided you choose a battery able of providing 500 amperes at more 8 volts for a minute at each launch. As show this picture.
Accumulator perhaps too feeble or bad gear ratio
View attachment 1144709
Yaw Mon. The first project using a car starter blew the fuse as they did not get the math right.
But they got the 2-speed transmission version to work on 12 volts.

This new one is using a brushless motor and many more KW is needed.
 

Vance

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Vance,
Thank you for your response. Can you tell me how many kW the starter is rated at.
Thanks
Skyjinks
I am down at the hangar and there is no data plate or stamped in numbers on the starter so I can't answer your question.

I use a an Odyssey PC 680 and in one very busy day I started the 320 cubic inch Lycoming engine and the rotor 45 times. Most of the flights were less than fifteen minutes so there was not much time for the battery to recharge.

When I have the pre-rotator engaged the system voltage drops from fourteen volts to eight volts and the radio stops working.

I do not recommend a car starter for a pre-rotator. It is my understanding their duty cycle is six seconds and they make a lot of heat.

Maximum torque is at stall so a car starter is hard on the mast.
 

Jean Claude

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I piloted gliders C800, Bijave, C 310, airplanes Piper J3 , PA 28, Jodel D117, DR 220, Cessna 150, C
Total Flight Time
About 500 h (FW + ultra light)
Vance, what is the ratio of the teeth number of crown /pinion ?
It seems to me 1400 rpm / 120 rpm = 12 is near enough to the best
 
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Jazzenjohn

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JC Almost every bendix/ringgear combination I've seen has been a 12-1 ratio with the possible exception of the Butterfly gyros.
 

Vance

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Vance, what is the ratio of the teeth number of crown /pinion ?
It seems to me 1400 rpm / 120 rpm = 12 is near enough to the best
I have a nine tooth pinion and my recollection is my ring gear is 114 teeth.

I have vague recollection of 108 and 118 so take my recollection for what it is worth.

I am working on a flight plan at home so I can't count them.

It is a geared starter and I don’t know what the ratio is.

Without blades the pre-rotator’s maxim rotor rpm was around 150 the last time I tested it.
 

ultracruiser41

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It’s pretty simple....I’ve used Toyota starters on all my gyros for pre-rotators. 27’ cruiser dragon wings and 27’SportCopter rotors.

No soft starts.... no extra junk.... just an odyssey battery... have only had 2 that needed replacing.... had them changed in 5 minutes. All rotors can easily get to cone by 110-130 rrpm. Never killed a battery...even after giving all day rides.

I will never use anything but electric....the simpler...the better. It really isn’t rocket science!!
 
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All_In

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Piper Archer, Aviomania G1sb
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Not sure over 10,000+ logged FW, 260+ ultralights, sailplane, hang-gliders
Barry that is KISS...
PRA new educational open source projects are hoping for 220 RRM. It is designed to bolt on the same drive cable and use the same Bendix etc. too.
 

Skyjinks

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I will look at it tomorrow and see if it is rated that way.
Thank you Vance any information regarding current rating etc., would be helpful.
Hello Charles, PRA (Popular Rotorcraft Association} has open source projects for educational purposed.
For Pre-rotators we have 1 soft start circuit using a car starter that can also be a 48-volt high-speed pre-rotator in our library. Members-only pages but will post here if you wish as we changed the new modern PRA to a tax-deductible, non-profit, charity that supports our community whether you support us or not. We still have valuable member benefits and are adding more all the time.

We also have just finished a new two-speed transmission pre-rotator using a cheap car starter with San Diego University senior students. PRA chapter 31 is testing.
See this link to learn more.... https://www.rotaryforum.com/threads...t-is-done-and-ready-for-more-testing.1144536/

This year we have 5 projects with S.D.S.U., S.D.U, and UCLA has reached out but they are 1.5 hours from San Diego. They would have to come to us for testing.
One of those projects is another prerotator you might want to wait for and S.D.U. will be continuing to improve our first prerotator project this next year.
Projects
1) State of the art high-speed (at least 220 RRM with 30' blades) lightweight prerotator using a brushless motor, lithium batteries, and controller. With all things lightweight and powerful it will be expensive.
2) G'force impact fuel-cut-off-switch.
3) Test-stand to test pre-rotators, drive systems, and different manufacturers rotor-blades with data-logger.
4) Lightweight stop and drop landing gear with anti-tip-over (self-leveling on impact).
5) Jump-take-off system to retrofit the fleet. Adapt a helicopter rotor head add electric drive system for jump-take-off capability.

Now I have 3 colleges fighting over PRA projects. But PRA can only pay for the parts for one project at a time. May ask for donations to run all 5 at all 3 colleges is the only way we could let them all try at the same time.

Hello Charles, PRA (Popular Rotorcraft Association} has open source projects for educational purposed.
For Pre-rotators we have 1 soft start circuit using a car starter that can also be a 48-volt high-speed pre-rotator in our library. Members-only pages but will post here if you wish as we changed the new modern PRA to a tax-deductible, non-profit, charity that supports our community whether you support us or not. We still have valuable member benefits and are adding more all the time.

We also have just finished a new two-speed transmission pre-rotator using a cheap car starter with San Diego University senior students. PRA chapter 31 is testing.
See this link to learn more.... https://www.rotaryforum.com/threads...t-is-done-and-ready-for-more-testing.1144536/

This year we have 5 projects with S.D.S.U., S.D.U, and UCLA has reached out but they are 1.5 hours from San Diego. They would have to come to us for testing.
One of those projects is another prerotator you might want to wait for and S.D.U. will be continuing to improve our first prerotator project this next year.
Projects
1) State of the art high-speed (at least 220 RRM with 30' blades) lightweight prerotator using a brushless motor, lithium batteries, and controller. With all things lightweight and powerful it will be expensive.
2) G'force impact fuel-cut-off-switch.
3) Test-stand to test pre-rotators, drive systems, and different manufacturers rotor-blades with data-logger.
4) Lightweight stop and drop landing gear with anti-tip-over (self-leveling on impact).
5) Jump-take-off system to retrofit the fleet. Adapt a helicopter rotor head add electric drive system for jump-take-off capability.

Now I have 3 colleges fighting over PRA projects. But PRA can only pay for the parts for one project at a time. May ask for donations to run all 5 at all 3 colleges is the only way we could let them all try at the same time.
All-In, thank you, a lot of interesting information, just need some time to digest. Where do I send a donation to the research? Thanks to all for responding so far I'll get back when I have more time.
 

Jean Claude

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Messages
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Location
Centre FRANCE
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I piloted gliders C800, Bijave, C 310, airplanes Piper J3 , PA 28, Jodel D117, DR 220, Cessna 150, C
Total Flight Time
About 500 h (FW + ultra light)
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
 

Condor

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Thanks to all for the information. I am building the 'Bulldog' prototype with Charles (Skyjinks), hoping to test fly before the end of this year. The chassis is designed and will be built next week. I will post photos as we go along. Martyn
 

Kolibri

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Wolverine, that's an interesting way to do it. I expect there would be some gradual engagement of the rubber wheel,
acting as a sort of "soft start". What is your rotor diameter?

Regards,
Kolibri
 

Kolibri

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Thanks, and I wish you success in your experimentation.
It's an area ripe for electric options.
 
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