2 speed pre-rotor

[WHY]

Ok,----------got a question, anyone out there using one of the little toyota starter motors on a set of 23 ft (or less) Dragon Wings in a light single place, that would want to try a "cheap" motor controller (from China, claims to be a 12 to 40 volt and 100 amps ??).

If you think you got the kind of "tech" savy necessary to hook it up right and try it, I will consider buying it and if it BLOWS, it blows. It sure looks awful light to me and is very small, but I am willing to gamble in the interest of progress but don't have a machine to experiment on. What do you say ??????

Tony

[Alan_Cheatham]

Tony,

Do you have links to the motor and controller your talking about?

There should be enough specs and information out there to determine proper application without having to resort to smoke testing.

.

[WHY]

Hi Alan

All I have is the E-Bay listing, # 140357609275 , not much more info, I know on the bigger Permanent magnet starters you can get a starting surge amp of around 150 amps (they say) so I'm thinking maybe if the start load draw can be limited thru PWM maybe this little unit will handle the "running" load current (for at least a few tries ) . It does have a connector for a fan. It's the output and input terminals that spook me !!

Shipped from China it will only run about $80, It's not in a case or box , just the open circut board with the heat sinks.

Tony

[WHY]

When I say a "little" Toyota starter, I have seen them on different engines and rated anywhere from 1.2 kw up to around 1.8 kw but I don't know any model numbers to be able to identify which is which.

Tony

[Alan_Cheatham]

Doesn't look to me like that controller will have the capacity for running a starter motor without burning up, I'm sure that 1200 watt rating is only for very brief moments of use.

Unless there is some overiding need to use a PWM controller I feel the simple resistor-wire soft start is fine for prerotators using automotive starters.

.

[WHY]

Looks like a "Kelly" KDS-24200 12/24 volt 200 amp , less than 2 lbs (plus hardware and contactor) on sale at $119 is the best buy if your thinking PWM for a brushed motor.

Tony

[WHY]

Well it is a long way down the road, but since I will probably be trying electric pre-rotation when I get around to it, I decided to go ahead and order the "KELLY KDS-24200" and have it on hand. Will post some pics when I get it, will see what the quality is, it is from China direct.

Tony

[WHY]

Run on to a good tid bit of information,---- on E-bay item # 230795556431, is a Hitachi replacement starter "MOTOR ONLY" --------3HP !!!!! new for less than $70 !!

I think I will order one of these to play with, make my own end housing with the output bearing and a mounting for the 2 x 2 mast and have my machinist friend make some kind of coupling to mate over the drive gear to a telescoping shaft to the bendix on the head then combine this with the PWM Kelly DC motor controller and see what happens ??

Tony

[Alan_Cheatham]

Tony, what advantages do you perceive a PWM controller will have over the traditional two speed resistor wire soft start, especially since you want to combine it with an automotive starter motor?

.

[WHY]

Hi Alan

Well, I'm pretty much shade tree, when it comes to design, but the voltage drop by the resistor wire waste a lot of battery energy in the first few seconds in the form or a lot of heat. also I am hoping that by using a PWM this will sort of give the effect of allowing the motor to slowly build power while there is a lot of inertia in the blades, sort of like "slipping the clutch" on a transmission that has lost low gear. Then once the blades get some momentum, bring up the ratio on the PWM with the control potieniometer to full power at the top end. Since this motor was made to drive a "spur gear" reduction I may not have enough reduction at the top, as I will not be using the reduction unit or the bendix engagement solenoid on the motor itself. I plan to mount the motor down on the mast and have a short sliding shaft up to the bendix on the rotorhead. The other possible headache might be if the motor turns the wrong way.

Tony

[JEFF TIPTON]

Depending on the starter motor, you might be able to index the end plate at the brushes ninety dgrees to reverse the rotation. You would need a bendix for the other rotation.

[WHY]

Hi Jeff

That's good to know, you can go to E-bay and look at the motor, might have to drill new bolt holes but that could maybe be done. Do you know what the appx ratio is on the typical rotorhead starter/ring ??

Tony

[JEFF TIPTON]

Just taking a quess at the headthe ring gear is around 86 teeth and the bendis is around 11 teeth. I counted teeth on some pictures that I have of other gyros.

Ballbark ratio is 7 or 8 to 1.

[WHY]

Thanks Jeff

Tony

[Brent_Brown]

I think it is 10 to 1 that is why I would like to use a V belt between with a sprag on the motor side so the blades can rev past the e-motor when it can or when the e-motor is off in flight. A small clutch like this one in the pic should be mounted to the e-motor. I will have to draw it up later so you can see and you could still mount the e-motor low on the mast or right on the head.