GyroRon
Former Gyro know it all
- Joined
- Oct 29, 2003
- Messages
- 16,920
- Location
- Fort Mill South Carolina
- Aircraft
- Vans RV4 / Dominator 582 Ultrawhite
- Total Flight Time
- ALOT
As some of you may be aware from this thread https://www.rotaryforum.com/forum/showthread.php?t=17836
Well anyway this past saturday I did some experiments to see what the problem was with my loss of rpms. I also had bought a new / Used prop to put on my gyro and wanted to do some thrust tests and flight tests to see if I could make sence of all this.
So to really shorten up what my problem was in the first thread, I had a bolt go through my Kiev prop at Mentone and I replaced the Kiev with a slightly smaller diameter sport prop. The sport prop had painted tips that the paint was chipped away from it in places, almost as if it had been sandblasted briefly, and then the leading edges of the blades had a layer of glue stuck to them from leading edge tape that used to be on the blades. At mentone I set the prop pitch to give me about 6800 rpms static and the prop performed really well. I got home from Mentone and used Acetone and a rag and wiped off the glue on the leading edge of the blades and also wiped off the paint from the tips. The next flight I made the engine rpms struggled to reach over 6000 rpms in climb and maxed out static at maybe 6300 rpms. Something had changed since Mentone and I was curious what it was.
So this past Saturday I did some messing around with the gyro.
The first thing I did was to fly the gyro as it sat after the previous flight from the weekend before were I noticed the loss of power. This time there might have been a ever so slight increase in power, almost unnoticable really and I can only think the cooler less humid air had something to do with that. I might have had 50 more engine rpms on average than the weekend before. For all intents and purposes the performance was the same as the weekend before and the " problem " still existed.
So I tried something to see if my guess on loss of performance was right. I took plain old grey Duct tape and split it in half, giving me a strip of tape nearly the same width on the prop that the old glue strip had left ( I could still see where the glue was due to the prop being blacker in color where the glue was ) So I applied the duct tape over the leading edge of the prop replicating the width and length of the old leading edge tape and glue. I then took the gyro out to the runway and took it for a short flight. Right off the bat the rpms were back to almost the level they were at at Mentone.
I don't think the Duct tape was as thick as the old glue residue and of course the duct tape did nothing to replicate the chipped paint on the tips, but this told me that my cleaning up of the prop was enough to radically change the effective pitch of the prop, and explained the loss of performance.
So I rolled the gyro out to the runup area so I would have the gyro on pavement and backed my truck out to the edge of the runup area. I took off the tailwheel and attached a tie down strap to where the wheel goes and then hooked the strap to my scale and attached the scale to my towing hitch on the truck.
With Barry Kropliens help I removed the Duct tape and with the engine slightly warmed up we ran a thrust test. This was with no tape on the blades and we achieved a max rpms of 6480 and a max thrust of 380 lbs.
All my thrust tests have had a simular result and that is when the pull first starts the rpms peak out and you get the highest rpms and highest thrust, but within a few seconds the rpms start to drop off a little and thrust drops off a little as well. I can only guess that this is due to the heat building up in the engine and a reduction of power
So back to the first thrust test with no tape, the rpms peaked at 6480 and thrust at 380 lbs, but within a few seconds the rpms tapers down to a steady 6340 rpms and thrust drops to 365lbs. Not exactly show stopping performance but not bad considering the rpms and smaller diameter.
So then I put duct tape back over the leading edges, this time I used one layer of duct tape the same width of the original glue strip, and then added a second layer the same width but only about half as long as the bottom layer. Then we fired up the engine and ran another thrust test. With the tape was saw max rpms of 6780 and after it tapered off it settled at 6520 rpms. Very interesting was the thrust generated did not change, it peaked at 380 lbs at 6780 rpms and settled at around 365lbs at 6520 rpms.
Could not understand why the thrust did not change with the increase of rpms....
So just to satisify my doubts, we repitched the Sport Prop and took out one degree of pitch at the tips. We also removed the duct tape, and retested the gyro. This time we saw 7040 rpms peak and thrust max of 440 lbs and tapering off rpm wise to 6880 rpms and 400 lbs of thrust.
Very interesting!
So the next thing I wanted to do was to put my Kiev prop back on and try the thrust test on it. I decided not to, because the prop has a damaged blade and I am not sure how safe that blade is in it's damaged state, and also just due to time constrants I didn't feel like taking the time to mount up the prop and set the pitch etc.... I did do a thrust test on this prop when I installed the engine the gyro has on it now, and this test was done on gravel in less than ideal conditions and it pulled somewhere around 440-450 lbs peak at about 6500-6600 rpms. This same prop with the original engine the gyro had ( same model Rotax 618, but it had been bored out twice to maximum oversize pistons, the engine on the gyro now has standard bore pistons in it so less overall power ) pulled a max of 465lbs
I had to leave the airport for a while to go to Tim Moses house to pick up my Warp Drive, Tim trimmed the tips down from what was a 72 inch Warp drive down to the same size as my Kiev, which was the largest prop my gyro could accept, I believe the size is 70.9 inches in diameter. After leaving Tims place I had to go to Ace Hardware to get new bolts to bolt the prop on, then I went and had lunch. I came back to the airport and spent about a hour putting the prop together and mounting it all up.
I had to take it out and do a test run to set where the rpms were with the pitch randomly set at 9.5 degrees out at the tips, and max rpms were only about 5800-5900 rpms. I re pitched the prop to 8 degrees at the tips and took the gyro over to the thrust test area and hooked it back up to the truck and scale... Also worth noting was it was at least 10 degrees hotter outside by this time and it felt more humid as well.
So tied up to the scale I did one last rpm/thrust run and got almost the same exact rpms at the last run with the sport prop, just under 7000 rpms max and a max pull that was off the scale! The scale goes to 440 lbs and the needle went off the scale to about where 450-455 lbs would be located if the scale went higher. Of course as the temp built up in the engine rpms dropped to around 6700 rpms and thrust was reduced to about 425 lbs.
I don't remember what the Kiev prop would settle at after the engine built up some heat, we were always just concerned with peak thrust. I would have to assume that it too would taper down to the same levels I saw with the Warpdrive.
So anyway, there was alot of surprising things I learned from this testing. And one thing that surprised me is the warp drive prop really didn't give up much if anything performance wise to the Kiev. I like the kiev prop, and the sport prop. Both seem lighter and look nicer. But both are hollow foam filled fiberglass or carbon fiber props, and both are easily damaged if something like a bolt goes through them. I feel the Warp drive is a better choice if something goes through it, it is harder to damage to begin with and easily fixed.
I had already put the warp drive on the gyro and didn't want to take it off to weight it, but I did weight the sport prop and the kiev..... The sport props blades weighted 1 lbs .98 oz each, and the hub was 3lbs 10.8 oz. the Kiev blades were 1 lbs 11.3 oz each and the hub was 2 lbs 14.4 oz.
Well anyway this past saturday I did some experiments to see what the problem was with my loss of rpms. I also had bought a new / Used prop to put on my gyro and wanted to do some thrust tests and flight tests to see if I could make sence of all this.
So to really shorten up what my problem was in the first thread, I had a bolt go through my Kiev prop at Mentone and I replaced the Kiev with a slightly smaller diameter sport prop. The sport prop had painted tips that the paint was chipped away from it in places, almost as if it had been sandblasted briefly, and then the leading edges of the blades had a layer of glue stuck to them from leading edge tape that used to be on the blades. At mentone I set the prop pitch to give me about 6800 rpms static and the prop performed really well. I got home from Mentone and used Acetone and a rag and wiped off the glue on the leading edge of the blades and also wiped off the paint from the tips. The next flight I made the engine rpms struggled to reach over 6000 rpms in climb and maxed out static at maybe 6300 rpms. Something had changed since Mentone and I was curious what it was.
So this past Saturday I did some messing around with the gyro.
The first thing I did was to fly the gyro as it sat after the previous flight from the weekend before were I noticed the loss of power. This time there might have been a ever so slight increase in power, almost unnoticable really and I can only think the cooler less humid air had something to do with that. I might have had 50 more engine rpms on average than the weekend before. For all intents and purposes the performance was the same as the weekend before and the " problem " still existed.
So I tried something to see if my guess on loss of performance was right. I took plain old grey Duct tape and split it in half, giving me a strip of tape nearly the same width on the prop that the old glue strip had left ( I could still see where the glue was due to the prop being blacker in color where the glue was ) So I applied the duct tape over the leading edge of the prop replicating the width and length of the old leading edge tape and glue. I then took the gyro out to the runway and took it for a short flight. Right off the bat the rpms were back to almost the level they were at at Mentone.
I don't think the Duct tape was as thick as the old glue residue and of course the duct tape did nothing to replicate the chipped paint on the tips, but this told me that my cleaning up of the prop was enough to radically change the effective pitch of the prop, and explained the loss of performance.
So I rolled the gyro out to the runup area so I would have the gyro on pavement and backed my truck out to the edge of the runup area. I took off the tailwheel and attached a tie down strap to where the wheel goes and then hooked the strap to my scale and attached the scale to my towing hitch on the truck.
With Barry Kropliens help I removed the Duct tape and with the engine slightly warmed up we ran a thrust test. This was with no tape on the blades and we achieved a max rpms of 6480 and a max thrust of 380 lbs.
All my thrust tests have had a simular result and that is when the pull first starts the rpms peak out and you get the highest rpms and highest thrust, but within a few seconds the rpms start to drop off a little and thrust drops off a little as well. I can only guess that this is due to the heat building up in the engine and a reduction of power
So back to the first thrust test with no tape, the rpms peaked at 6480 and thrust at 380 lbs, but within a few seconds the rpms tapers down to a steady 6340 rpms and thrust drops to 365lbs. Not exactly show stopping performance but not bad considering the rpms and smaller diameter.
So then I put duct tape back over the leading edges, this time I used one layer of duct tape the same width of the original glue strip, and then added a second layer the same width but only about half as long as the bottom layer. Then we fired up the engine and ran another thrust test. With the tape was saw max rpms of 6780 and after it tapered off it settled at 6520 rpms. Very interesting was the thrust generated did not change, it peaked at 380 lbs at 6780 rpms and settled at around 365lbs at 6520 rpms.
Could not understand why the thrust did not change with the increase of rpms....
So just to satisify my doubts, we repitched the Sport Prop and took out one degree of pitch at the tips. We also removed the duct tape, and retested the gyro. This time we saw 7040 rpms peak and thrust max of 440 lbs and tapering off rpm wise to 6880 rpms and 400 lbs of thrust.
Very interesting!
So the next thing I wanted to do was to put my Kiev prop back on and try the thrust test on it. I decided not to, because the prop has a damaged blade and I am not sure how safe that blade is in it's damaged state, and also just due to time constrants I didn't feel like taking the time to mount up the prop and set the pitch etc.... I did do a thrust test on this prop when I installed the engine the gyro has on it now, and this test was done on gravel in less than ideal conditions and it pulled somewhere around 440-450 lbs peak at about 6500-6600 rpms. This same prop with the original engine the gyro had ( same model Rotax 618, but it had been bored out twice to maximum oversize pistons, the engine on the gyro now has standard bore pistons in it so less overall power ) pulled a max of 465lbs
I had to leave the airport for a while to go to Tim Moses house to pick up my Warp Drive, Tim trimmed the tips down from what was a 72 inch Warp drive down to the same size as my Kiev, which was the largest prop my gyro could accept, I believe the size is 70.9 inches in diameter. After leaving Tims place I had to go to Ace Hardware to get new bolts to bolt the prop on, then I went and had lunch. I came back to the airport and spent about a hour putting the prop together and mounting it all up.
I had to take it out and do a test run to set where the rpms were with the pitch randomly set at 9.5 degrees out at the tips, and max rpms were only about 5800-5900 rpms. I re pitched the prop to 8 degrees at the tips and took the gyro over to the thrust test area and hooked it back up to the truck and scale... Also worth noting was it was at least 10 degrees hotter outside by this time and it felt more humid as well.
So tied up to the scale I did one last rpm/thrust run and got almost the same exact rpms at the last run with the sport prop, just under 7000 rpms max and a max pull that was off the scale! The scale goes to 440 lbs and the needle went off the scale to about where 450-455 lbs would be located if the scale went higher. Of course as the temp built up in the engine rpms dropped to around 6700 rpms and thrust was reduced to about 425 lbs.
I don't remember what the Kiev prop would settle at after the engine built up some heat, we were always just concerned with peak thrust. I would have to assume that it too would taper down to the same levels I saw with the Warpdrive.
So anyway, there was alot of surprising things I learned from this testing. And one thing that surprised me is the warp drive prop really didn't give up much if anything performance wise to the Kiev. I like the kiev prop, and the sport prop. Both seem lighter and look nicer. But both are hollow foam filled fiberglass or carbon fiber props, and both are easily damaged if something like a bolt goes through them. I feel the Warp drive is a better choice if something goes through it, it is harder to damage to begin with and easily fixed.
I had already put the warp drive on the gyro and didn't want to take it off to weight it, but I did weight the sport prop and the kiev..... The sport props blades weighted 1 lbs .98 oz each, and the hub was 3lbs 10.8 oz. the Kiev blades were 1 lbs 11.3 oz each and the hub was 2 lbs 14.4 oz.
![[RotaryForum.com] - Interesting experiment with props and thrust testing](https://data3.rotaryforum.com/attachments/40/40929-468bba4e5fdb4b59d4c1e13044b127de.jpg?hash=uFrYjPGIOr)
