TF 1/5 Scale P-51 ARF Assembly (1ST MISHAP!!!)
03-05-2015, 09:16 AM
#3477
After I finished the RimFire 65cc-Varioprop runup yesterday on disassembly I found that the prop had slipped back on the spinner back plate making contact between the blade trailing edges and the cone. The back plate has fine knurling but the Varioprop hub is smooth metal. I have to find a way to increase friction to prevent slippage. It is hard to hold the Varioprop hub and get enough torque on the prop nut. I am going to try roughing the smooth hub and increasing the knurling on the back plate. I can't hold the blades for tightening- it would over stress and break them. It needs a spanner tool to hold the hub. May try gluing sandpaper to the back of the hub. I did not have slippage when I ran it on the 50cc motor. There is a big difference in motor torque between the 2 motors. Any way it means more testing before I can risk flying this setup.
03-07-2015, 01:54 PM
#3478
peak rpm was 6514 during the speed run-way too high. I will set the pitch at 18 and fly again tomorrow.
peak Watts was 5580-close to previous testing using an APC 26-15 Electric prop.
Max current was 134.7amps-the APC drew 164amps.
motor temp after shut down-slightly warm. Rimfire 65cc.
Battery temp-slightly warm
minimum voltage was 41.3volts-the APC prop would pull it down to 27volts. Batteries are a 6 pack of Hobby People 3200mah 4s 30c wired as 12s 2p=6400mah 50.4 volts.
Total capacity used was 2263mah out of 3200mah per cell.
maximum ESC temp was 98.3-Castle 160HVF
The flight went ok, I just need data for a baseline. The first landing attempt didn't go as hoped at 4 minute and 20 seconds so I added a lot of power and raised the gear for a quick go round. The next landing approach worked well, slight skip and smooth rollout. A strong NE crosswind caused it to swing left at the end of the rollout, I knew it would happen so let it turn off into the grass. No damage.
I got a good video of the flight and will post it on youtube tonight with a link here
03-07-2015, 08:21 PM
#3480
mark Ix,
After flying the 4 blade today I think the 65cc motor is going to work better using larger diameter and higher pitch. Ramoser makes bigger props so I am going to explore that and continue with the 22.6 set at higher pitch (18-20 inches) to load the motor down more as the 16inch setting allows rpm to exceed the 4800 max for this set of blades. Another option is to get the 19-20 inch diameter blade set that has a higher max rpm although I believe the climb may suffer. I bought a set of 24-16 inch blades with the Zinger 4 blade hub. If I can get that prop bolted on the 65cc motor as I have already tried it may be the solution.
Incidentally, my Prop chart show the pitch speed I got today is around 110mph. I think the adrenalin was flowing as the plane seemed to be flying slowly but when I viewed the video it was obviously moving right along-most of the flight was at half throttle until I did the speed pass and then gave it the gun on the missed approach to climb out and try again. The video shows that I did not have enough throttle on the first approach. You can hear more power on the 2nd successful landing attempt.
After flying the 4 blade today I think the 65cc motor is going to work better using larger diameter and higher pitch. Ramoser makes bigger props so I am going to explore that and continue with the 22.6 set at higher pitch (18-20 inches) to load the motor down more as the 16inch setting allows rpm to exceed the 4800 max for this set of blades. Another option is to get the 19-20 inch diameter blade set that has a higher max rpm although I believe the climb may suffer. I bought a set of 24-16 inch blades with the Zinger 4 blade hub. If I can get that prop bolted on the 65cc motor as I have already tried it may be the solution.
Incidentally, my Prop chart show the pitch speed I got today is around 110mph. I think the adrenalin was flowing as the plane seemed to be flying slowly but when I viewed the video it was obviously moving right along-most of the flight was at half throttle until I did the speed pass and then gave it the gun on the missed approach to climb out and try again. The video shows that I did not have enough throttle on the first approach. You can hear more power on the 2nd successful landing attempt.
03-09-2015, 12:46 PM
#3481
My Feedback: (9)
SJ, That prop really looks like it belongs there in the pic above. I agree, looks like the R65 is the right motor for these size props. I am also beginng to see that your Castle 160 HVF ESC is a good chioce as well. I was considering a 200A ESC but maybe that's overkill. Trying to cool it in a Spitfire maybe more challenging that in the P-51, though.
I think Biela makes a 23x14x4 blade prop as well. Seems to a reasonable price, around $150. I was looking into the mounting problem with the Zinger prop and the R65 shaft length. Have you looked at having Dave Brown Products make a special prop nut for the application? Look at the pdf info on his web page under Vortec prop adapters.
BTW E-Calc predicted:
Zinger 22x16x4 - 5733 Watts, 155Amps, and 5442 PRM
Biela 23x14x4 - 5858 Watts, 160Amps, and 5402 RPM. It's encouraging that you numbers are in the same ball park.
Mark
I think Biela makes a 23x14x4 blade prop as well. Seems to a reasonable price, around $150. I was looking into the mounting problem with the Zinger prop and the R65 shaft length. Have you looked at having Dave Brown Products make a special prop nut for the application? Look at the pdf info on his web page under Vortec prop adapters.
BTW E-Calc predicted:
Zinger 22x16x4 - 5733 Watts, 155Amps, and 5442 PRM
Biela 23x14x4 - 5858 Watts, 160Amps, and 5402 RPM. It's encouraging that you numbers are in the same ball park.
Mark
Last edited by mark IX; 03-09-2015 at 01:01 PM.
03-09-2015, 07:00 PM
#3482
mark IX,
I increased the pitch to 18 inches and flew again on Sunday. The results were better but the power of the R 65cc motor is still over-revving the 22.6 blades and I only used close to full throttle once during the flight when I executed a miss approach and went around for another try.
If you look at these csv snapshots you will see that they are all of the same data download. The relevant part of each is the left hand flight of three flights. The second and third flights were made with different props as I wanted to not risk damaging the 4 blade but wanted to continue flying with some other warbird pilots who had a P 47 and a corsair. On the second flt. using a APC 26-15 the light winds changed suddenly (thermal?) from east to west and I got a nose over tendency as it reached TO speed. I cut power as the blade tips scraped the pavement and it lifted off. Adding power I did one lap and landed. No damage except the prop tips so I put an XOAR 24-14 on and continued the flight as the right hand side of the chart shows. The bottom line of the charts shows max data for these last two flights. If you look at the cursor position at about 2:40 in the first pic the current reaches 147.1amps, watts 6486, rpm 5327, this is the take off power with the gear down and climbing out. The cursor pos. in pic 2 the gear is up and the plane has accelerated to a higher speed but current has dropped to 86.6amps, watts to 3830, rpm is way up to 5962, about 1162rpm higher the prop's design limit of 4800rpm. Chart prop speed calculates to around 108mph. The cursor position in the third pic is at the go around point for another approach which the guys in the club watching liked, I managed a smooth wheel landing and taxied back to change batteries and the prop.
My next move is to raise the pitch angle to 20 inches and try it again. I am already of the opinion that I should have bought the larger Varioprop 32i hub with 26.6 blades. You could use the 25.9 inch blades for your spitfire. This larger prop system is rated to 7300rpm for the 26.6inch blades and 7800rpm for the 25.9inch blades which are shaped like Spitfire blades. I don't like the idea of having a prop blow up on me as I have personally witnessed three full scale helicopters come apart after 2 main rotor and 1 tail rotor blowup and have been on a couple of recovery missions to crash sites of a UH1B and a Hughes OH6A that both lost tail rotors and went down hard enough to junk the airframes although the crews were OK.
An advantage of the bigger props is the flaps work better and the torque problem when the tail comes up is easier to handle. Another option would be to lower the throttle servo upper limit to control the over-rev with the 16-d Varioprop.
I increased the pitch to 18 inches and flew again on Sunday. The results were better but the power of the R 65cc motor is still over-revving the 22.6 blades and I only used close to full throttle once during the flight when I executed a miss approach and went around for another try.
My next move is to raise the pitch angle to 20 inches and try it again. I am already of the opinion that I should have bought the larger Varioprop 32i hub with 26.6 blades. You could use the 25.9 inch blades for your spitfire. This larger prop system is rated to 7300rpm for the 26.6inch blades and 7800rpm for the 25.9inch blades which are shaped like Spitfire blades. I don't like the idea of having a prop blow up on me as I have personally witnessed three full scale helicopters come apart after 2 main rotor and 1 tail rotor blowup and have been on a couple of recovery missions to crash sites of a UH1B and a Hughes OH6A that both lost tail rotors and went down hard enough to junk the airframes although the crews were OK.
An advantage of the bigger props is the flaps work better and the torque problem when the tail comes up is easier to handle. Another option would be to lower the throttle servo upper limit to control the over-rev with the 16-d Varioprop.
03-09-2015, 07:26 PM
#3483
I have a couple of prop nuts that have the prop side machined to fit a prop washer. I picked one and reamed the front prop hub plate to fit ( On the Zinger 22-14 4 blade). It works and I can tighten it enough but there are only 3 turns to tighten so I am going to see if I can get a Vortech or Tru-turn nut with a deeper cut. The standard nut for my ZDZ 80 is .327in. thick so I would like at least that much thread for this kind of power. The Zinger prop with its thicker wood blades would limit rpm on its own and would handle over-revs with out blowing up.
03-09-2015, 07:39 PM
#3484
The Castle 160 HVF has a built in cooling fan so as long as you supply it with its own outside air supply it runs cool. I have put 170amps through it and it did not heat up. I have seen smaller electric and gas powered Spitfires use blow in doors under the nose for cooling. I think Dave Platt did this many years ago. You just have to move the air through the fuse and provide an exit further back. I have an ESC air exit cut in the lower firewall (an angled ramp). Nobody notices it unless it is inverted on the stand. I have a fuel filler and tank vent for the DA 50 mounted there and the no-spark button for arming the Rimfire motors also. They cant be seen in flight. You would have to baffle the air between the motor and ESC so that the ESC does not get hot air from the motor.
03-10-2015, 03:19 PM
#3485
My Feedback: (9)
Looks like I will be able to turn that 24x16x4 that I wanted to use in the first place. Based on your performance curves that is. I don't think I have enough ground clearance for a 25" prop. That motor looks as though it has plenty of power for the larger prop. It'll be interesting to see what diff the 24" 4 blade Zinger makes, although I think the motor will be able to handle it ok.
BTW, what do you have for sound system in the Mustang? It sounds pretty realistic.
Mark
BTW, what do you have for sound system in the Mustang? It sounds pretty realistic.
Mark
Last edited by mark IX; 03-10-2015 at 03:22 PM.
03-10-2015, 04:55 PM
#3486
It is my opinion based on my limited experience that if you can get the Zinger 24x16x4 bolted on to the RF 65cc motor it will work and there probably is less danger of prop failure because the blades are thick wood. I am sure that it can turn larger props. My setup now turns anything I can get bolted on. The current draw even on the biggest props is manageable, I have had to learn how to set up the ESC so that the defaults don't cause emergency landings, some thing that happened several times in the beginning. My good luck in saving the plane when the ESC decided to cut power at the wrong time to save itself or the battery packs couldn't have lasted. Each time power was lost unexpectedly it was a white knuckle experience and just barely made it back for dead stick gear up slides in the grass. And now with the electric gear that takes ten seconds to get into the wing I am glad that I have that phase of the learning curve behind me. Another factor is the change to 12s 2p packs that have a little more duration and have already made it possible to wave off and go around for a better landing.
The sounds are Benedini from Aerosound. I have the 12 volt amplifier with the Mini sound card. It works best on 4s lipo packs, you can turn the volume up all the way on the amp and when installing firmware turn the volume up all the way there too. They sell a 50 volt amp that will run off the motor packs but my system has current draw close to 2amps so I didn't want that draining my motor packs. I bought the small magnet speakers from Aerosound but later got some high wattage car stereo speakers with larger magnets from best buy. People like the way it sounds but it isn't loud enough for me. The club event announcer approached me about finding a way to send the sound by WIFI to the PA system. I am researching possibilities on this now. My 2 speakers are in the bottom of the wing behind the spars and this works good when the plane is low over or on the runway, the sound bounces in all directions. A disadvantage of the Varioprop is that it flies silent. People really like the prop rip of the various 2 blades I have tried. When the plane is at the ends of a pass the prop rip can be heard when the sound amp isn't loud enough. I think mounting an additional sound amp in the fuse to power 2 more speakers or transducers would g a long way towards this. I could Y the sound feed from the Mini card to feed 2 amps and 4 speakers. Benedini in Germany has listings for several larger sizes of transducers. One of these is so powerful it can shake a plane severely, possibly causing fatigue damage to the airframe.
The sounds are Benedini from Aerosound. I have the 12 volt amplifier with the Mini sound card. It works best on 4s lipo packs, you can turn the volume up all the way on the amp and when installing firmware turn the volume up all the way there too. They sell a 50 volt amp that will run off the motor packs but my system has current draw close to 2amps so I didn't want that draining my motor packs. I bought the small magnet speakers from Aerosound but later got some high wattage car stereo speakers with larger magnets from best buy. People like the way it sounds but it isn't loud enough for me. The club event announcer approached me about finding a way to send the sound by WIFI to the PA system. I am researching possibilities on this now. My 2 speakers are in the bottom of the wing behind the spars and this works good when the plane is low over or on the runway, the sound bounces in all directions. A disadvantage of the Varioprop is that it flies silent. People really like the prop rip of the various 2 blades I have tried. When the plane is at the ends of a pass the prop rip can be heard when the sound amp isn't loud enough. I think mounting an additional sound amp in the fuse to power 2 more speakers or transducers would g a long way towards this. I could Y the sound feed from the Mini card to feed 2 amps and 4 speakers. Benedini in Germany has listings for several larger sizes of transducers. One of these is so powerful it can shake a plane severely, possibly causing fatigue damage to the airframe.
03-10-2015, 05:18 PM
#3487
My Feedback: (9)
The other question had was the fan for your ESC. Does that have a dedicated battery or do you have it y-cabled into where you plug your ESC into your Rx?
So if I understand your charts above, correctly, with the Vario prop set at 18 pitch your amp draw was 147.1, Watts at 6486, and the rpm was 5327, all at TO, right? And during flight, the prop unloaded to 86.6 amps, Watts at 3830, and the rpm was 6952. Did you feel the model was moving noticably faster with the 18 vs 16 pitch? How as the flight time and were you using the 12S, 2p battery setup?
Thanx, Mark
So if I understand your charts above, correctly, with the Vario prop set at 18 pitch your amp draw was 147.1, Watts at 6486, and the rpm was 5327, all at TO, right? And during flight, the prop unloaded to 86.6 amps, Watts at 3830, and the rpm was 6952. Did you feel the model was moving noticably faster with the 18 vs 16 pitch? How as the flight time and were you using the 12S, 2p battery setup?
Thanx, Mark
Last edited by mark IX; 03-10-2015 at 05:24 PM.
03-10-2015, 08:15 PM
#3488
I'm sure the plane would fly faster if I ran it full throttle but I have had structural failures with the TF ARF at high speeds so always throttle back to keep it at about 100mph. The idea behind setting higher pitch is to lower the rpm to close to 5000 or lower, the design limit on the varioprop is 4800rpm. The current draw is a product of airframe drag and acceleration. When the gear is down and the plane is climbing out current draw is at its highest until the gears retract and it reaches the cruise speed you are comfortable with, then it drops to 70-90amps depending on air speed. When I had the prop set at 16 inches it would top out at around 110mph full throttle but rpm is way higher than it should be for this prop. Increasing pitch will allow much faster top speed but my plane isn't built for extreme speeds.
03-10-2015, 08:21 PM
#3489
On the fan, I have it on a servo y cable on the ESC channel. Turn the receiver on and the fan starts. It has a tiny current draw and I have 4000mah of receiver batteries. The Benedini has a 4 cell 2200mah lipo and the gear has a 2000mah battery in the wing. It is complex but it has worked fine.
03-14-2015, 05:08 PM
#3491
mark IX,
I looked at all of the prop-spinner adapter nuts I have and picked one that had the right threads (10x1.25mm) a spinner nipple threaded 10-32 and the nut flats were like stacking 2 3/8-16 nuts with a groove between them. I think I got it from Dave brown years ago. Anyway, the prop side has a groove for a hard steel prop washer machined in it. I wanted the threaded part to be thicker so I found a washer with a 1/2 inch bore. I chucked the spinner nipple end into a 1/2 inch drill chuck and using a new stone in my Dremel carefully cut the prop side nut flats round then down to fit the 1/2 inch bore washer. I dressed the top of the ground part with a 4 corner file to a flat-square corner so there would be a machined flat for the prop washer. This all took about an hour. The next step was to ream the front side only of the Zinger 4 blade hub out to 1/2 inch. After cleaning up all the edges it all bolted up to the RimFire 65cc motor and gave me 10 turns tight on the new prop nut, enough to do the job and mostly free. I may be able to test fly it tomorrow if the weather is better than today. I will be using the Zinger 22-16 blade set first but I think it will work better with the 24-16 set of blades.
I looked at all of the prop-spinner adapter nuts I have and picked one that had the right threads (10x1.25mm) a spinner nipple threaded 10-32 and the nut flats were like stacking 2 3/8-16 nuts with a groove between them. I think I got it from Dave brown years ago. Anyway, the prop side has a groove for a hard steel prop washer machined in it. I wanted the threaded part to be thicker so I found a washer with a 1/2 inch bore. I chucked the spinner nipple end into a 1/2 inch drill chuck and using a new stone in my Dremel carefully cut the prop side nut flats round then down to fit the 1/2 inch bore washer. I dressed the top of the ground part with a 4 corner file to a flat-square corner so there would be a machined flat for the prop washer. This all took about an hour. The next step was to ream the front side only of the Zinger 4 blade hub out to 1/2 inch. After cleaning up all the edges it all bolted up to the RimFire 65cc motor and gave me 10 turns tight on the new prop nut, enough to do the job and mostly free. I may be able to test fly it tomorrow if the weather is better than today. I will be using the Zinger 22-16 blade set first but I think it will work better with the 24-16 set of blades.
03-15-2015, 06:58 AM
#3492
My Feedback: (9)
Do you have a pictures of the finished parts? I had a similar idea from looking at the Zinger prop on line. It looked like the top plate of the hub assembly could be altered to allow a nut to protrude down onto the R65 threaded shaft as you described. Can't wait to see what performance results you get with this prop.
Mark
Mark
03-15-2015, 04:32 PM
#3493
Last edited by sjhanc; 03-18-2015 at 07:48 AM. Reason: correction
03-16-2015, 06:53 AM
#3494
My Feedback: (9)
I assume you flew the 22x16x4 Zinger, not the 24" version right? It's interesting that the Zinger is drawing a lot more amps, being a lower pitch, than the Vario prop. Is the Zinger heavier? According the motor specs its rated for 7500W continuous and 8400W burst. Looks like this prop is really challenging the motor. 80mph, though, is the speed range I was hoping for. Any change you can put your gps device in the cockpit to confirm the speed you are getting?
Mark
Mark
Last edited by mark IX; 03-16-2015 at 09:22 AM.
03-16-2015, 10:11 AM
#3495
I did fly the 22 inch blades. These blades have a really thick airfoil which probably accounts for the higher amp draw and lower rpms. Choosing a smaller blade set should also get a thinner airfoil and get both rpm up and lower amp draw. The Zinger is heavier and I have to modify my battery shelf to allow the packs to move back for correct CG. On the Varioprop, there is the possibility that the airfoil stalls on acceleration at high speeds in which case rpm would burst to a high peak then decrease as the plane catches up. The only way to verify this is a speed sensor. I was recording speed readouts with an action cam aimed at an old smart phone-the phone has become unreliable now and will only work when the charger is connected. It occurred to me that if I run the phone on a 12 volt charging cord for cars that might get around this problem. I have already tried a new phone battery. I bought an onboard speed sensor that requires me to cut into the wing to mount it out of the prop blast, I haven't got around to that yet. And it only saves the highest speed reached. It might give variable speeds that a camera could record, at least on one run up to max speed. My plan was to mount it on an angled pylon attached to one of the gear access panels.
03-16-2015, 10:34 AM
#3496
I just finished recharging the flight pack I used to fly the Varioprop. It took 1500mah to recharge so that means I landed with 1700mah per cell unused in a 4 minute flight. It also means the Varioprop is very efficient, using less battery capacity than even the best 2 blade props I have used.
03-16-2015, 11:21 AM
#3497
After charging the battery pack used to fly the Zinger 22-16 4 blade prop 1620mah out of 3300mah per cell was used in a 3 minute flight, so 4 minute flts. are possible with the Zinger leaving enough for 1 go round, maybe 2. It is cutting it close for electric power so this prop would be better suited for 80-100cc gas motors where flt. duration would not be a problem. If Zinger could supply his 4 blade with electric blades efficiency would be much better.
03-16-2015, 03:44 PM
#3498
My Feedback: (9)
My goal is the stay as close to the 24" diameter scale size as possible. What current draw did you see with the Zinger 22x 16x 4 blade prop? RPM? Was the motor excessively hot? I was figuring on a 4-5 minute flight time with 12S and 6000mah batteries. I could go to 8000mah size but I was concerned with the added 2 lbs of weight. It sounds like from your experience, that flight time should be achievable. Also you mentioned the speed was around 80 mph which is also what I expected.
Thanx, Mark
Thanx, Mark
03-16-2015, 05:05 PM
#3499
It breaks down like this; Zinger 22-16 4 blade Tru-Turn spinner.
TO- current peak-161.4, peak draw varied between 147-178amps for the flight-average about 90amps. Rpm reached 5517 soon after gear up. Chart speed=90mph.
Rpm peak during the speed run-5921rpm chart speed is 100mph at that rpm. It was hard to estimate speeds visually because of very strong west winds, I kept it high in case of trouble.
Motor temp was slightly warmer than usual-140degrees f. I have very good motor cooling. Ambient temp at ground level close to 90f.
ESC temp was high through out the flight reaching a peak of 178.4f soon after TO and a low of 147.3f at gear down for LDG. TO to full stop was 4 minutes.
The ESC gets pretty good cooling air flow and no hot air from the motor so it was working hard turning this prop.
I only did moderate climbs during the flight- no diving for speed. I typically climb into a turn to shorten the turn radius and descend back to the same altitude for straight runs. There were no other planes up during the flight. Climb performance was adequate for a 30 lb. plane. I forgot to start the camera so got only a little video.
Battery temp. was slightly warm. The weather was hot, blue sky, west winds down the runway at 15-18mph, winds at 75-150 feet were 25-35, lots of thermals. Down wind passes were going like X$@#!, upwind seemed like 55-60mph. The weak link with this prop is the high ESC temps.
TO- current peak-161.4, peak draw varied between 147-178amps for the flight-average about 90amps. Rpm reached 5517 soon after gear up. Chart speed=90mph.
Rpm peak during the speed run-5921rpm chart speed is 100mph at that rpm. It was hard to estimate speeds visually because of very strong west winds, I kept it high in case of trouble.
Motor temp was slightly warmer than usual-140degrees f. I have very good motor cooling. Ambient temp at ground level close to 90f.
ESC temp was high through out the flight reaching a peak of 178.4f soon after TO and a low of 147.3f at gear down for LDG. TO to full stop was 4 minutes.
The ESC gets pretty good cooling air flow and no hot air from the motor so it was working hard turning this prop.
I only did moderate climbs during the flight- no diving for speed. I typically climb into a turn to shorten the turn radius and descend back to the same altitude for straight runs. There were no other planes up during the flight. Climb performance was adequate for a 30 lb. plane. I forgot to start the camera so got only a little video.
Battery temp. was slightly warm. The weather was hot, blue sky, west winds down the runway at 15-18mph, winds at 75-150 feet were 25-35, lots of thermals. Down wind passes were going like X$@#!, upwind seemed like 55-60mph. The weak link with this prop is the high ESC temps.
