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Monkworkz VS. B&C

Mark33

Well Known Member
I'd like to see a few comments from people who’s had experience with both the Monkworkz 30 amp generator and the B&C 20 amp backup alternator. I feel confident that these are both great products and probably can't go wrong with either one, but other than the weight differences, if you had both of them sitting in front of you, which one would you pick up and install?...and why?
 
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I have installed and flown with both. What I can report:
- Both work as advertised.
- The 20 amp B&C alternator install is slightly more compicated as the external regulator needs to be on the cabin side of the firewall.
- The B&C alternator needs external voltage to get started.
- The Monkworkz Generator install is straight forward. It does require two blast tubes off the back baffle wall.
- I ran both of these in the “Standby” configuration. Here the B&C, as does the MonkworKz, picks up the load as buss voltage drops (as happens if you primary alternator fails). The transition is seamless. The B&C will then hold buss voltage as whatever you set the voltage regulator at - typically 13.5 to 13.8 or so (cannot be much higher in the standby mode). The Monkworkz however will bring up buss voltage from that pickup point back to 14.2 or so. The difference is the B&C analog voltage regulator vs the Monkworkz software defined control module.
- For the new RV-10 project I’ll install another Monkworkz.

Carl
 
I have the 3rd option which is PlanePower's 6lbs, internally regulated, 30A FS1-14 backup alternator. No issues with it. The B & C option is slightly lighter (5.75 lbs alternator only) and less expensive, but you do have to mount an external regulator. Otherwise the B&C and PlanePower units are very similar. No experience with the Monkworkz device.
 
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I have installed and flown with both. What I can report:
- Both work as advertised.
- The 20 amp B&C alternator install is slightly more compicated as the external regulator needs to be on the cabin side of the firewall.
- The B&C alternator needs external voltage to get started.
- The Monkworkz Generator install is straight forward. It does require two blast tubes off the back baffle wall.
- I ran both of these in the “Standby” configuration. Here the B&C, as does the MonkworKz, picks up the load as buss voltage drops (as happens if you primary alternator fails). The transition is seamless. The B&C will then hold buss voltage as whatever you set the voltage regulator at - typically 13.5 to 13.8 or so (cannot be much higher in the standby mode). The Monkworkz however will bring up buss voltage from that pickup point back to 14.2 or so. The difference is the B&C analog voltage regulator vs the Monkworkz software defined control module.
- For the new RV-10 project I’ll install another Monkworkz.

Carl

Thanks Carl, that’s a great report!
 
I have the 3rd option which is PlanePower's 6lbs, internally regulated, 30A FS1-14 backup alternator. No issues with it. The B & C option is slightly lighter (5.75 lbs alternator only) and less expensive, but you do have to mount an external regulator. Otherwise the B&C and PlanePower units are very similar. No experience with the Monkworkz device.

Thanks Todd…good food for thought!
 
I'd like to see a few comments from people that's had experience with both the Monkworkz 30 amp generator and the B&C 20 amp backup alternator.

I know I don't qualify to answer your question since I have not had first hand experience with that model B&C but I will give you my impression of pros and cons since I have had experience with other models of B&C and have seen that model installed.
B&C Pro:
No cooling blast tube required
Very reputable with many of them in the field

Cons:
Physically bigger, heavier and harder to install

Monkworkz Pro:
Lighter, smaller and more amps
Very easy to install

Cons:Requires two blasting tubes
Not as many in the field but also no report of issues that I have heard of

Concerns:
My biggest concern with the Monkworkz, possibly unfounded, is that it has a single bearing to support a relatively heavy piece of magnet turning at high speed. I have not look inside to see what safeguards are in place to prevent the moving part from ever letting go but if it ever does, it will prove to be a very bad day.
 
I ran the BC 20A BU for 10+ years, no issues, (never needed it with a primary BC 40A).
I swapped it out around a year ago for the MW, mainly because I was putting the plane on a diet.
Both units work great, no issues.
If I was going on an around the world venture I'd opt for the BC, it's been around a lot longer and has a proven track record, the MW is still in its infancy and long-term reliability is still unknown. But so far, I like it!
 
...........My biggest concern with the Monkworkz, possibly unfounded, is that it has a single bearing to support a relatively heavy piece of magnet turning at high speed. ............

Actually the MW has a 10mm dia shaft pressed into the aft end of the rotor, runs the full length of the rotor and exits out the front where it is attached to the frangible spline drive adapter. That shaft is supported at both ends by sealed ball bearings.

If those bearings were to fail, the rotor would rub against the stator which would overload the frangible adapter, causing it to break such that the splined section would just free-wheel in the vacuum pump adapter shaft. So, a totally benign failure scenario (other than it also stops electrical output!). And the rotor is a stout part made to withstand much higher RPM than it sees on the vacuum pump pad (3510 RPM max on a Lyc). I'm actually working on a different application of this unit which spins the rotor at 9000 RPM.
 
I have a yet to be installed Monkworkz generator.

I'm a huge B&C fan and have one of their main alternators. One of the reasons I chose Monkworkz over B&C for the backup role was that it does not require field current. If it is turning, it is working, simple as that.
 
Actually the MW has a 10mm dia shaft pressed into the aft end of the rotor, runs the full length of the rotor and exits out the front where it is attached to the frangible spline drive adapter. That shaft is supported at both ends by sealed ball bearings.

If those bearings were to fail, the rotor would rub against the stator which would overload the frangible adapter, causing it to break such that the splined section would just free-wheel in the vacuum pump adapter shaft. So, a totally benign failure scenario (other than it also stops electrical output!). And the rotor is a stout part made to withstand much higher RPM than it sees on the vacuum pump pad (3510 RPM max on a Lyc). I'm actually working on a different application of this unit which spins the rotor at 9000 RPM.

I am puzzled here, are you saying there are two bearings on both end of the shaft?
I installed one and the aft side is the moving part with no housing or stationary part to incorporate a bearing. As I understand it, there is only one bearing on the shaft which is between the moving part and the part that gets bolted to the engine block.
 
Thank you gentlemen for the replies. I think one of the benefits to the MW generator is that it doesn’t need a battery to excite the field. I know B&C has been around for a long time and has a great reputation and MW appears to be building a strong following as well. After reading the comments, and as expected, I’m sure either product could be installed and used with confidence.
 
I am puzzled here, are you saying there are two bearings on both end of the shaft?
I installed one and the aft side is the moving part with no housing or stationary part to incorporate a bearing. As I understand it, there is only one bearing on the shaft which is between the moving part and the part that gets bolted to the engine block.

I threw together a quick CAD diagram below to help you visualize it. The shaft is pressed into the back of the outer rotor shell (gray) such that it rotates with the rotor. The shaft is supported at each end with a single bearing. The bearings are blue. The inner stator (green) fills the full length of the outer rotor. The OD's of the bearings are supported by the stator at each end. Remember that the green stator is stationary and the rotor spins around the outside of the stator (backwards from traditional alternators which have the rotor spinning inside of the stationary stator).

x-sec.jpg x-sec2.jpg
 
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MW

I chose and installed it -why? -1. it is smaller and allows more room for my oil filter change, 2. It has 30 amp continuous output, and a distant 3. it is lighter.

I agree with Walt, it does not have enough hrs in service to be "proven", but as a backup hopefully will not fail at the very time it is needed. I am quite familiar with the brushless technology and in theory if it passes 50 hrs it will be very long lived.
 
Aesthetics

I bought a MW generator to review. The lighter weight always good and seems very robust. Since my primary alternator was B&C it was just easier to stack the 2 regulators together on the cold side of the firewall using stand-offs. Probably not a great reason but been very happy with the set-up on the 14 (now over 400 hrs) and did not think of a strong reason to change. I think either MW or B&C you can’t go wrong.
 
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I threw together a quick CAD diagram below to help you visualize it. The shaft is pressed into the back of the outer rotor shell (gray) such that it rotates with the rotor. The shaft is supported at each end with a single bearing. The bearings are blue. The inner stator (green) fills the full length of the outer rotor. The OD's of the bearings are supported by the stator at each end. Remember that the green stator is stationary and the rotor spins around the outside of the stator (backwards from traditional alternators which have the rotor spinning inside of the stationary stator).

View attachment 43596 View attachment 43595
This goes to prove "a picture worth a thousand words"

Thank you very much for this visual aid and the explanation that goes with it. It does make sense now.
 
Plus testing

Actually the MW has a 10mm dia shaft pressed into the aft end of the rotor, runs the full length of the rotor and exits out the front where it is attached to the frangible spline drive adapter. That shaft is supported at both ends by sealed ball bearings.

If those bearings were to fail, the rotor would rub against the stator which would overload the frangible adapter, causing it to break such that the splined section would just free-wheel in the vacuum pump adapter shaft. So, a totally benign failure scenario (other than it also stops electrical output!). And the rotor is a stout part made to withstand much higher RPM than it sees on the vacuum pump pad (3510 RPM max on a Lyc). I'm actually working on a different application of this unit which spins the rotor at 9000 RPM.

On top of what the smart Mechanical Engineer said I've done accelerated wear testing to try to get the generator to come apart. I did 1 million cycles of 10, 20, 30 and 40 Gs of acceleration, all on the same test article and afterward the amount of wear was nearly imperceptible. And I have been running the same package at 9000 RPM with no issues.

The end bell of the generator is supported by two bearings ganged together, because that's where the bulk of the load is, and then mounted end is supported by one bearing. They're rated for 45,000 RPM.
 
I bought a MW generator to review. The lighter weight always good and seems very robust. Since my primary alternator was B&C it was just easier to stack the 2 regulators together on the cold cold side of the firewall using stand-offs. Probably not a great reason but been very happy with the set-up on the 14 (now over 400 hrs) and did not think of a strong reason to change. I think either MW or B&C you can’t go wrong.

So you put the MW regulator box on the cold side of the firewall along with the B&C regulator?
 
One add to the other pro/cons is that if you would like to use the B&C 90 degree oil adapter, on the -10 (not sure about others) it requires a 1.5" extension to clear the engine mount. Then if you want to use the B&C 401H 20a as bu alt, it requires a 0.75" extension to clear the oil adapter extension. The MW wouldn't need the alternator extension because of it's smaller package.

B&C 410H + regulator ~$850 + extension kit $650
MW $995
 
I'd like to see a few comments from people who’s had experience with both the Monkworkz 30 amp generator and the B&C 20 amp backup alternator. I feel confident that these are both great products and probably can't go wrong with either one, but other than the weight differences, if you had both of them sitting in front of you, which one would you pick up and install?...and why?

One thing about the SD-20 alternator from B&C, it is not a 20 amp alternator. I talked with the B&C rep and he mentioned it was a poorly named product because the output will be more than 20 amps. In fact, he stated it will produce 30 amps. The new data sheets show the output as more than 20 amps. That is a question you may direct to B&C. It has been a while since I talked with them and the fine details are getting a little fuzzy.
 
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