- This topic has 24 replies, 4 voices, and was last updated 14 years, 4 months ago by
.
-
Posts
-
Here are the results of bench testing this motor, a.k.a “Super Park Jet”. First of all, it is not a 2350 kv motor. Tests show motor parameters of: kv = 1930 RPM/volt, Io = 1.42 amps, Rm = .185 ohm. Also, the motor weight is more like 40 grams vs. the 32 grams advertised. Test equipment as follows:
Battery: Dualsky 3S, 850 mah, 25C
Controller: Phoenix 25
Prop Blades: Graupner 7.5 x 4 folder
Hub: BB Aluminum with 32 mm pin spacing
Effective prop diameter = 7.8 inches
Battery fully charged at start. No recharge between runs.
Data taken 7.5 seconds into each run.Run__ Volts__ Amps__ Watts__ RPM
1___ 10.11 __ 19.5 __ 197___ 12,600
2___ 10.20 __ 19.7 __ 201___ 12,660
3___ 10.16 __ 19.5 __ 198___ 12,570
4___ 10.12 __ 19.4 __ 196___ 12,480Thanks Dick, this is good information. I still believe this to be a good fit for some models. Particularly on 4 cells. The one drawback that I have found is that all of the LS motors are fragile. They do not survive encounters with the ground very well. Most of the Axi’s that I have , have spent time subterranean and are still making good watts.
What would happen with a smaller prop?
7.8 x 4 is what a KB 3.5 turns.I have looked at this motor, wondering about a 1/2A sized plane.
Jim, I’ll heed your warning and try to avoid encounters with terra firma. The LS SPJ motor, with the Dualsky 3S battery is a nice, lightweight combo drawing 200 watts. This is plenty of power for a plane of say 400 to 450 sq. inches. However, I agree that 4S is the wave of the future. I recently picked up on sale, an Enerland 700 mah 30C 4S pack. Tried it yesterday with my MicroDan 2510 1360 kv motor and the same prop as above. Wow, got 15,210 RPM, with 300 watts in, at 21.3 amps. Now that is serious power! Can’t wait to try it in a plane. BTW, The Enerland 4S pack comes very, very close the the F1Q 90 gram weight limit. With about 1 inch cut off the leads, and a Deans Ultra connector added, the pack weight came out at 89.62 grams.
Dan, When you reduce the prop size you reduce the load on the motor. It’s true that RPM’s will go up a little, but the amp draw will go down, so the motor will not be pushing as hard as it could. Overall thrust would be much lower.
I think of a 1/2 A plane as having about 240 sq. inches. For that, I would choose a smaller motor that’s lighter and being pushed harder. Consider the LS “Park Jet” motor at 2800 kv and a 6 x 3 prop. With 3S, this should draw about 170 watts at very high RPM. You will need a battery and a controller capable of sustaining at least 16 amps. However, the weight may of these components may be too much for a 1/2A size plane.
DickDick, I fioure 1/2A about the same- 240-270.
I understand about reducing the draw with the smaller prop. I wondered about maybe 6×5 or something. Smaller d with more pitch as an option.
The little park jet sounds intriguing. A 30k 6×3 should make a 1/2A plane go pretty hard. Actually a lot of 1/2As would need a stiffer wing.My rig uses a 400 mah battery. Full, its 12.56 volts. After a 15 sec run its still about 12.3 volts. I’m trying to figure some stuff out. If I ran it 4 cells with the same controller-8 amp , would it burn up the controller? Or the motor? I’m figuring that the event will winnow to a 5 sec motor. Maybe w/ 4 cells it wouldn’t have time to cook at 5 seconds?
I’d be interested in trying it. You recommended a 300mah battery before. Maybe a 300mah battery at 4 cells would weigh about the same. I’m figuring a re-charge after every flight here. That’s not necessary with what I have now. i’ve made 4 flights without re-charging with no problems maxing. 10-15 second runs.Dan, I’m not quite sure how to respond to your questions. We are all learning as we go. I know this: if you go to 4S you will have to decrease prop size to keep the operating current within reasonable range of the motor, battery, and controller ratings. However, the short motor runs we use allows all components to be overdriven on a short term basis. That’s what we want .. lightweight parts being driven hard. Remember, there are no ready-made 4-cell packs available in small sizes, except for the Everland 700 mah 30C, and that is not a light pack. You will have to wire together two 2-cell packs. Also, there is only a very limited choice of folding prop sizes. However, as we go to smaller props, non-folders would probably be o.k. I am surprised that you can get 4 flights on a 400 mah pack, but I don’t know all the details of your rig. I do know it flys well … I’ve seen it. Dick
Hey , my learning curve is mostly a straight line.
I kinda figured we could over drive them for our short runs. I’m a bit nervous about doing my own pack doubling. I’m guessing I’d just plug them into a two-fer and go forward. I’m wondering how much abuse the controller would take. jim says I’m drawing 8 amps now. Another cell would bump that up.
I have completed the 1/2A Marval for electric. It uses the AXI 2204-54. 3 cells. 8 amp Jeti. I have it set up with a 7×5 APC prop. Non-folder. It uses an O-ring to attach the prop. Servo DT. All up weight–7.2oz for 270 squares. I’ll fly it at Seguin this weekend, assuming the wind will stay below 30 knots. Its trimmed better than the Maverick, has better power to weight, higher aspect ratio. It looks to be better than the Maverick. Not as good as Jim’s bigger Maverick but its what I’ve got.Are you and your dad going to King Orange?
Dan,
Is the new model the same airframe as recently published in MA?
How about posting a picture?
Cheers!Dan, Richard Jr. and Sr. will not be going to King Orange this year. We usually fly commercial airlines to Florida. For us, it’s too far to drive from Boston. However, this year Ed Luparelli is out, so we have no one to transport our gear down there.
I think you can make a 4-cell pack with help from Jim and me. You want to hook the 2 packs in series. I think you use bullet connectors on Jim’s advice. If so, just make a short jumper cable to plug into the minus of one pack and the plus of the other. The remaining 2 wires will be the plus and minus of the 4-cell pack. DickPete, I don’t have a pic yet. Imagine the exact same wing and stab from the magazine(cause that’s what it is) with a new fuselage. Battery is in the pylon. Bigger prop. Otherwise it looks the same.
Dick, sorry to hear that you won’t be at KOI.
I’m comfortable with making a 4 cell pack. I don’t know how to figure if the motor or controller will carry it. The specs for the controller call for 2-3 cells. I understand that playing with the prop will affect the amp draw. Other than the expensive empirical test, how can we determine what the motor will handle? Same question applies to the controller.
Obviously, this a problem for us with the electric stuff. We have a large database to help with gas engines when determining prop and plane size. With the electrics we have a very small base that is constantly changing.
Testing to destruction is kinda pricey. Rumor has it that Frank Pollard has done a lot of this type of testing. Jim has done some as well. I’m not up for it, myself. That’s why I’m flying the rig that I have. It could use a bit more power. Its not where the VA powered plane is at 5 seconds.Dan,
I’ll try to get a shot of the new A385E tomorrowso you won’t have to wait ’til Saturday to get a look.
If you can’t do the same, I’ll be looking forward to seeing yours then.
Faust is converting one of his existing Mavericks for this contest.
It wouldn’t surprise me if Dick Wood turned up with a new ship too.
Anybody else you know of?
Cheers!
P.S I’m working up a set of floats for mine so as to ready for Nationals.Dan,
Right you are.
Start a new thread on a new topic.
I cancelled my order for the “Park Jet” today, guessing that it probably won’t deliver the promised 2800KV.
Cheers!Back to the original post.
I haven’t run a tach on my AXI motor so don’t know for sure the rpm. The book says 1400 rpm per volt. At the end of a flight, I’m over 12 volts. I had the same prop-7.5×4. The book tells me I’m supposed to get 16,800 rpm. The motor weighs 1 oz-28gms. It uses a 400mah 3cell battery. Its 88 watts, I think.When I read the original post re the Little Screamer, I’m thinking my package is a lot better power. Less battery,less controller,less motor weight. The package flys the 1/2A plane fine. I wouldn’t think it could haul a 400″ ship for beans.
The turns chart indicates that package is getting 12,5 k per volt. The revised specs indicated 1930 kv. I’d hafta re-think the prop on the LS.
Even so, it would be tough to imagine it could be better than the AXI on my rig.I’m not crowing here, I got the package from Jennings. I can take absolutely no credit for figuring it out. I gather that the LS is intended for a ducted fan. Wouldn’t that translate to a relatively small prop?
Do you have a 6×4 that you try?
- You must be logged in to reply to this topic.