Greetings,
Couple quick mentions before I get into the testing:
1. The generator all up weight is 2 lbs, 9 oz, so pretty close to 2.5 lbs rather than the 3 lbs I have been saying. 3 lbs was an estimate when going from a prototype plastic regulator enclosure to the aluminum enclosure plus adding some dampening silicon, but its closer to 2.5 lbs.
2. I have reworked the installation manual, its on the website monkworkz.com. The only substantive change is that I'm recommending a fuse/breaker be installed on the far end of the wire feeding the bus. This could be an existing breaker in retrofit applications. If there was chafing and that wire shorted it could bring your entire bus down or start a fire and so a fuse is needed on the far end in addition to the one I provide on the board. I intend on adding a suitable fuse to the kit.
Finally, on to the differential pressure testing:
TLDR: There is a 1.5% drop when you use both ducts as required for cooling.
To recap: I did some initial testing and measurements on the cowling pressure differential with and with out the required ducts for my generator. The measured pressure differential varied by more than the measured difference between runs with and without ducts. This testing was with 28 gauge needles in line with the meter. You can see that info here. If you try this break the needles off so you don't impale yourself.
Today I used 31 gauge needles around a foot from the meter to smooth out the jitter in the pressure measurements, this made for much more consistent, repeatable measurements. The set up is still very sensitive: a 1 knot change in airspeed quickly causes an observable pressure change on the meter. I also did the testing over the ocean to avoid turbulence.
Testing was done today, 10/10/21.
Speeds tested were same as before, 100 knots and 150 knots indicated from my Dynon IAS.
All the runs were very nearly the same conditions:
altitude: 2500 ft
OAT: 72-74
Altimeter 29.94-29.96 inHg
DA:3900-4040 ft
Run 1:
no ducts/holes taped over with stainless steel foil tape from both sides
100 knots: 5.26/5.30 min/max inH2O, 5.28 average inH2O
150 knots: 10.28/10.28 min/max inH2O, 10.28 average inH2O
Run 2:
2x 0.75" holes completely open
100 knots: 5.02/5.14 min/max inH2O, 5.08 average inH2O
150 knots: 10.24/10.28 min/max inH2O, 10.26 average inH2O
Run 3:
2x ducts for Monkworkz generator
100 knots: 5.18/5.22 min/max inH2O, 5.2 average inH2O
150 knots: 10.24/10.28 min/max inH2O, 10.26 average inH2O
Pressure drop across the cylinders is reduced by:
3.8% for open holes and 1.5% when the ducts are attached at 100 knots.
At 150 knots holes vs ducts doesn't make any difference, and its 0.19% reduction compared to sealed up holes.
I put together an album that starts with a picture of the syringe bodies in line with the measurement lines. After that there are pictures and videos. Each of the sets of videos is "book ended" by pictures of the state of the ducts for those runs. That album is here.
The measurements jive well with the testers reporting no CHT issues with the ducts being installed on their planes and also jive well with the previous testing, just much less noise in the measurements and that gives more insight into what is going on. If you watch the videos you'll see that the pressure changes we're talking about here from adding the ducts could just as easily be attributed to a 1 knot change in airspeed!
If you read this far... Thanks!
Bill
monkworkz.com
Couple quick mentions before I get into the testing:
1. The generator all up weight is 2 lbs, 9 oz, so pretty close to 2.5 lbs rather than the 3 lbs I have been saying. 3 lbs was an estimate when going from a prototype plastic regulator enclosure to the aluminum enclosure plus adding some dampening silicon, but its closer to 2.5 lbs.
2. I have reworked the installation manual, its on the website monkworkz.com. The only substantive change is that I'm recommending a fuse/breaker be installed on the far end of the wire feeding the bus. This could be an existing breaker in retrofit applications. If there was chafing and that wire shorted it could bring your entire bus down or start a fire and so a fuse is needed on the far end in addition to the one I provide on the board. I intend on adding a suitable fuse to the kit.
Finally, on to the differential pressure testing:
TLDR: There is a 1.5% drop when you use both ducts as required for cooling.
To recap: I did some initial testing and measurements on the cowling pressure differential with and with out the required ducts for my generator. The measured pressure differential varied by more than the measured difference between runs with and without ducts. This testing was with 28 gauge needles in line with the meter. You can see that info here. If you try this break the needles off so you don't impale yourself.
Today I used 31 gauge needles around a foot from the meter to smooth out the jitter in the pressure measurements, this made for much more consistent, repeatable measurements. The set up is still very sensitive: a 1 knot change in airspeed quickly causes an observable pressure change on the meter. I also did the testing over the ocean to avoid turbulence.
Testing was done today, 10/10/21.
Speeds tested were same as before, 100 knots and 150 knots indicated from my Dynon IAS.
All the runs were very nearly the same conditions:
altitude: 2500 ft
OAT: 72-74
Altimeter 29.94-29.96 inHg
DA:3900-4040 ft
Run 1:
no ducts/holes taped over with stainless steel foil tape from both sides
100 knots: 5.26/5.30 min/max inH2O, 5.28 average inH2O
150 knots: 10.28/10.28 min/max inH2O, 10.28 average inH2O
Run 2:
2x 0.75" holes completely open
100 knots: 5.02/5.14 min/max inH2O, 5.08 average inH2O
150 knots: 10.24/10.28 min/max inH2O, 10.26 average inH2O
Run 3:
2x ducts for Monkworkz generator
100 knots: 5.18/5.22 min/max inH2O, 5.2 average inH2O
150 knots: 10.24/10.28 min/max inH2O, 10.26 average inH2O
Pressure drop across the cylinders is reduced by:
3.8% for open holes and 1.5% when the ducts are attached at 100 knots.
At 150 knots holes vs ducts doesn't make any difference, and its 0.19% reduction compared to sealed up holes.
I put together an album that starts with a picture of the syringe bodies in line with the measurement lines. After that there are pictures and videos. Each of the sets of videos is "book ended" by pictures of the state of the ducts for those runs. That album is here.
The measurements jive well with the testers reporting no CHT issues with the ducts being installed on their planes and also jive well with the previous testing, just much less noise in the measurements and that gives more insight into what is going on. If you watch the videos you'll see that the pressure changes we're talking about here from adding the ducts could just as easily be attributed to a 1 knot change in airspeed!
If you read this far... Thanks!
Bill
monkworkz.com
