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monkworkz 05-05-2022 10:25 PM

2.6 lb, 30 amp Monkworkz Generator Intro Videos

I made a couple of videos talking about the 2.6 lb, 30 amp vac pad generator I developed and have been selling:

Bench Demo

I'll be working up an installation video as well.

Hopefully this better illuminates why I developed it, what it does and how it works.

Hit me up if you have any questions.

They are available now, $995 plus shipping. Email me at if you're interested.


ChuckGant 05-06-2022 07:22 AM

Great video, and awesome looking product. I'm definitely interested.

sailvi767 05-06-2022 07:28 AM

Can you compare it to the 40 amp B&C and what the advantages might be over that option?

jneves 05-06-2022 08:53 AM

Bill, very well presented. I'm a future customer for sure when the time comes to swap out the old mags for electronic ignition and the panel upgrade! Welcome advance for us EAB folks.

Freemasm 05-06-2022 09:14 AM

Quick Observations

Originally Posted by sailvi767 (Post 1606660)
Can you compare it to the 40 amp B&C and what the advantages might be over that option?

There's no single perfect application for such or the industry would have settled on it a long time ago. Quick technical observations keeping in mind I'm ME not EE. These could very well be incorrect.

- weight
- no excitation
- relative size

- Requires blast cooling; one each dyno and control module.
- Parasitic load. PMs versus excitation will have a permanent load from engine acc drive versus an alt
- Cost (slight)

- details on the moving case/device would be beneficial, Assuming part of outer case spins?
- Digital Control module versus dumb solid state stuff
- Installs that could take advantage of size (engine to FW) are (broadly generally) the ones that can least afford engine cooling air drains.

I'm sure there's more. My biggest curiosity are the parasitic loads. Hopefully the OEM reads and replies. Having options benefits some of us directly and all of us indirectly.

William 05-06-2022 09:35 AM

Hi Bill what type of moisture protection does the generator and regulator have?

Bill D

monkworkz 05-06-2022 12:46 PM

More details
Thanks for the replies.

Parasitic load:
I think this is in the noise.
When there is no load on these generators they basically present very little resistance, so with no electrical load almost no parasitic load. You can easily spin the generator by hand and it will coast for a couple of rotations. There is minimal "cogging" where the rotor feels like it gets stuck in ruts made by the permanent magnets.

As an aside, the orange generators to have substantial cogging, like will lurch forward forcibly in your hand, but I suspect that overall they have very little parasitic load as well when you average the torque for a full rotation. The magnetic field has to be pushed through but then also gives a push, and averages out to ~0. The orange generator is like pushing a car up and down hills, the monkworkz generator is like pushing a car on a flat road, both averaging out to around the same energy for distances that include many climbs and descents and have zero net elevation gain.)

However if you short the leads together it feels like you're churning ice cream, still very smooth, and the faster you try to spin it the more resistance it presents. But with no load there is very little mechanical resistance.

I have measured the mechanical to electrical efficiency and it's 90-95% in some case better than that, then the electrical efficiency of the regulator is substantially better still.

Alternators require the magnetic field to be actively generated and in rough numbers that's probably about a 10% efficiency hit, i.e. you need to put in around 1 amp of field to get 10 amps of current out. That will be less at higher RPM. Not something I have measured but that is generically how that works.

I would expect the Monkworkz device to be superior in mechanical to electrical efficiency at all RPM because it doesn't have to generate the magnetic field.

Anyway, parasitic loss is close to zero. If there is no load there is very little drag torque presented to the drive.

When it is actually making power there is loss in the conversion from mechanical to electrical power. Here is a quick worst case estimate of what the loss would be:

amps * volts = power
30 amps * 14.4 V = 432 watts <- call this power made good, why you bought the device

Power out /(regulator efficiency*Generator efficiency) = mechanical power required
432/(0.95*0.9) = 505 watts <- overall mechanical power harvested from your engine

lost power = 505-432 = 73 watts or ~0.1 HP. <- power you want to minimize

73 watts is high because the regulator efficiency is actually quite a bit better than 95%.

So even worst case scenario, the parasitic load is 0.1 HP, or less than 0.1% of the power output of most lycomings. Even if the alternator was a lot worse the parasitic load would still be in the noise(to me anyway).

But yes, whatever power is lost does need to be taken away with cooling and that is why there are blast tubes. The blast tubes are constrained to put the air directly where it is needed and nowhere else. I've measured the impact on cowling pressure differential with and without and it's less than the difference of 1 knot of airspeed.

Comparisons to other alternators:
I'm not an expert on other products, one tester, Dave Anders(with a very fast RV-4), claims that with a vac pad alternator he was not able to taxi and get a positive charge, he needed around 1400 (crank) RPM to show a positive charge, with the Monkworkz generator he gets away with ~1000 RPM. 1400 RPM is too much to taxi with and overspeeds his taxi or overheats his brakes.

Moisture protection:
The circuit board has a conformal coating baked on for moisture protection and lives in a machined 6061 box, the generator has sealant around the wire transitions. The construction isn't any different from other motors on your plane like in the starter or the alternator for that matter.



hohocc 05-06-2022 03:12 PM

I can't add to the tech discussion but I'm very impressed with your manner in both the videos and on VAF. Direct answers to questions where you have them, best guess answers when appropriate that are labelled as such, and good "facts only" videos where you compare to other manufacturers parts without beating on them all paints a great picture.
Clearly you know your subject well and you deserve to have your product do well.

Ironflight 05-06-2022 03:26 PM

I’ve been flying the Monkworkz generator on the back of the engine on my RV-8 for a couple of months now, and it has been flawless. With LED lighting, EFIS, modern radios….30 Amps is generally plenty, and I have done about half my flights with the Monkworkz only turned on, and the ND turned off.

I’ve got a full review coming in the July 2022 issue of Kitplanes….


BillL 05-06-2022 06:35 PM

Really excellent concept!!
I approached the alternator guys at OSH 15 yrs ago and asked if they were working on some smaller, lighter, more efficient, and longer life machines. SR, IPM, SPM something . . .Whaaat?? :eek:

For 95% efficient devices, why does it need two 3/4" hoses to keep cool? Are the windings rated for 130C? That seems like a lot of air, what is the assumed delta-P pressure for adequate cooling? I understand magnet temp requirement, but the rotating shell should provide the cooling there.

Is the "regulator" actually an AC-DC inverter to achieve the efficiency?

Claw pole alternators are only 55-60% efficient, higher amps and some don't need extra cooling.

I know heat has to go somewhere or temps just keep rising, but the cooling just seems a little high for an efficient SPM generator.

Are you going to be working toward a replacement for the short lived primary alternators?

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