UMS Evolution Radial Care and Operation
#1576
Roger I have a spare 7-77 I've set aside for parts I may be willing to part with. Brand new condition, but the only "gotcha" is they didn't include o-rings for whatever reason on the intake tubes...
#1577
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Thanks Tom,
I will look into one of the OS Carbs. I can machine it or an adapter for it . " Sometimes it pays to own a machine shop " <G> .
Roger, very sorry to hear about your Howard. That is my biggest fear with this engine, damaging it . If I was running a big gasser in the Corsair it wouldn't bother me in the least . Hopefully you will be able to track down the parts necessary to repair it.
Dave
I will look into one of the OS Carbs. I can machine it or an adapter for it . " Sometimes it pays to own a machine shop " <G> .
Roger, very sorry to hear about your Howard. That is my biggest fear with this engine, damaging it . If I was running a big gasser in the Corsair it wouldn't bother me in the least . Hopefully you will be able to track down the parts necessary to repair it.
Dave
#1578
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I did check with Horizon Hobby and it appears the repair costs would be at least as much or more that purchasing a new DLE 55RA. It seems a shame to me that one can't purchase parts and repair these engines ourselves. I think I could get by with a cylinder mounting ring with bolts and three valve push rods. I already have the push rods but the cylinder mounting ring is just not available. I am not sure I would have ventured into the radial engine world if I had realized one could not obtain repair parts. It looks as though I may also have a parts engine available. One thing that is so tempting is I have a new DLE 55RA sitting in its box under my bench. I was going to put that engine in a plane that I have not yet started but it may just end up in the Howard.
Best wishes and good safe flying.
Heli-NuBee (AKA Roger the radial rabbit)
Best wishes and good safe flying.
Heli-NuBee (AKA Roger the radial rabbit)
#1580
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Roger,
Let me take a look at my radial when I get home today. I might be able to machine you a new cyl. mntg. ring for your engine. I would probably either need a sample or a very good drawing of the part with the pertinent dimensions. . I don't need a cad drawing , just a clear sketch with the dimensions.
Dave
Let me take a look at my radial when I get home today. I might be able to machine you a new cyl. mntg. ring for your engine. I would probably either need a sample or a very good drawing of the part with the pertinent dimensions. . I don't need a cad drawing , just a clear sketch with the dimensions.
Dave
#1581
Join Date: Nov 2012
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Rodger, when my 77 ingested a broken cir clip from the crank shaft and damaged two cylinders and pistons I could not get horizon to just send me new parts so I could repair it myself. So I did finally send it in and they repaired it and sent it back in two weeks with no charge. Overall, I was happy with their service but like you, I would have preferred if they just provided the parts I needed but that is not the way they do it.
The amazing thing is that engine just kept running with two damaged cylinders, it just lost power. It wasn't until I opened it up that I knew what was wrong. I still love these things and will keep flying them as long as I can. I need something for the 99 since crashing the Howard though.
Tom N.
The amazing thing is that engine just kept running with two damaged cylinders, it just lost power. It wasn't until I opened it up that I knew what was wrong. I still love these things and will keep flying them as long as I can. I need something for the 99 since crashing the Howard though.
Tom N.
#1582
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OK, just want to inform you guys that you're a bad influence. For a long time, I'd been lusting for the little 735. However, logic always won out when I got too close to buying one. (Why would I pay that kind of cash for a complex 7 cylinder contraption when I could pick up an old ryobi for free at almost any place that services small engines devices? More power, no valves to ajjust, no expensive fuel, no expensive, hard-to-get parts, etc.!!!) All was going well until I came across this thread. After a couple of weeks of serious lurking, it was.... Order 735 from Horzon !!! Order "EVO Radial Fuel" from Ritches Brew !!! Order 2 "F" cells (glo plug power) off the web. ................... All was here Friday, but couldn't pass up a nice week end at the flying field, spending time with the other old geezers playing with their toys.. Got it mounted on the test stand, oiled all the visible, moving parts, & turned it over several times. As was mentioned here earlier, I also had 3 "soft" cylinders. Initial startup of the little jewel was a non-event. Spent more time finding where the barrel valve just opened, & setting the transmitter than anything else. Starts with just a bump of the starter, Top end needle adjustment is nice & broad, but I did have to adjust the bottom end needle much more rich than I'm accustomed to doing. Was the only way that I could get a nice low-end idle. Even with the rich setting, it ran fine with no glo-plug power. Head temperatures were so low that I questioned the IR unit. Only 'bout 50 deg. above ambient. Up to half throttle,this thing is so quiet. The average sewing machine makes more noise. Half to full throttle produces a nice "purr". No exhaust ring, just open stacks. Prop was a wood Top Flite 18x8. ( Same as I use on my Ryobi 31CC). RPMs were 6500+ (with a/f ratio a bit on the rich side). Idle, with the rich mixture was at 1900 RPMs Got 'bout 25 min. of run time. The 3 soft cylinders are still noticeably lower than the rest, but not nearly as bad as was before the run. I really feel confident about the engine. Doubt that I'll go through a long "break-in" on the test stand. Air frame is gonna be a counterfit Giant Stick. Sure would like to see this thing in a Stearman, but I've never had a bipe in the air. I'm comfortable with the Stick. Hope the weight is gonna be near (or under) 12,5 lbs. These things can sure be addictive !!! Haven't even got the wing halfs glued together on the Stick yet, and I'm already thinking "What plane would I like to put a 999 in"? ...............George K.
#1584
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Hi guys, sorry that I have been AWOL for awhile but my wife was and is having medical issues. Thanks for the offers guys but I will just set aside the engine for awhile like I did my Phoenix Mustang until I get the urge to deal with it. I am sure I will eventually get it repaired and back into service. For now though, I installed a DLE 55RA in the Howard and the plane is much lighter with this power plant which should result in easier landings. I'm sure the mood will strike me in the future when the right plane come along to repair and place the 7-77 back in service. However, today was great because I had the maiden flight on my new Phoenix P-51D 86" wing Mustang powered by a DLE 55RA and it went very well.
Best wishes and good safe flying;
Heli-NuBee (AKA Roger the radial rabbit)
Best wishes and good safe flying;
Heli-NuBee (AKA Roger the radial rabbit)
#1586
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just a recent flight on my Corsair. one vid from phone cam, and the other with a $40.00 key chain cam mounted in front of the canopy, turn volume down on out side cam because of the air noise. this has the Evolution 9-99
1. https://youtu.be/mKJK_3xvcz8
2. https://youtu.be/R0aBkZB7IUQ
1. https://youtu.be/mKJK_3xvcz8
2. https://youtu.be/R0aBkZB7IUQ
#1591
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I just re-installed the 7-77 into my repaired H9 60cc Corsair and will be using the Keleo exhaust ring. I noticed some interference with the main needle valve - will rubbing the ring cause any problems down the road? I might bush it with a piece of brass. Thanks---Ted
#1597
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Well folks, I bought a 7-77 at a price I could not pass up. As most of you know I have the 9-90 and 7-70 I bought from Hobby King long before Horizon Hobby began distribution. The engines are serving me well with over 150 flights each! When I was writing/reviewing the instructions for the engines for Horizon I recommended a 22x12 prop for the 7-70 (7-77). This is a good prop for the 7-70 running at 5000 rpm, but still on the small side. I use the Xoar 22x10 three blade on my corsair which ground rpm is if I recall around 4000. I have been breaking in my new 7-77 with a 22x10 low load prop and staying below full throttle. I was seeing really high rpms over 6000! I decided to to try a too big prop I had reserved for my 9-90, a 24x12 on this engine. To my surprise this engine turned it at 5100 rpm! Using my true power calculator from Germany and the one from Astro Flight, neither of which give false high HP numbers, came to 3.4 PS and 3.7 HP respectively. Guys, these are strong performance numbers! 3.7 HP divided by 5.7 pounds = a power to weight ratio of .65 HP/ lbs! No, not a DA 50 performance but, this much power from a model radial is exceptional. I have said this before the carbs are shy on fuel delivery, even with large id short tubing and a high mounted tank. The 7-77 also works much better if the full throttle position is 3/4 open on the carb. -Tom
#1598
Nice Maxam. You should try one of these on CDI ignition. I found the carb to have adequate fuel flow, and you don't need to sog up the motor by cranking the high-speed needle way back to drop RPMs. On the ground it's a bit deceiving, but in the air if you give it 3-4 clicks rich from peak it works great. Wonder what 6,350rpm on a 24x10 Mejzlik gives you in the calculator. That's what I'm able to obtain on CDI - very impressed with the power on my 2nd engine (first one was missing o-rings all the way around the intake tubes... not cool). I also found no need to limit this carb to 3/4 open, but in general... the carb on these engines is definitely not of good design or quality. It's pretty bad...
#1599
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C. Horner, That carbon prop must have a very low constant (easy to turn vs a thick wooden prop. My numbers indicate 5.5 HP using a constant of 1.21. I used a constant of 1.31 which fits SEP and Xoar props reasonably well. Glow always produces more power than gas. Even DA races their engines on glow! Also the engine is running too fast. In the air it will unload another 1000 rpm in a dive! The constant for APC props is1.11 so I wonder if Mejzlik has an even lower constant. -Tom
#1600
Maxam, I have the prop constant for the Mejzlik. I'll post it for you tomorrow I wouldn't doubt based on what I'm seeing, that it's pushing 5HP. Very large gains with my setup and 16% nitro.
I don't pin the throttle for more than a small handful of seconds at most, so not too worried. Mostly fly at half throttle or so; and it seems to cope well anyhow without overheating, as well as I am checking valve clearance regularly. The rated RPM is on the ground as well don't forget... David Payne of Horizon runs his off onboard glow, with a 22x12 Mejzlik, pushing 6,250 on the ground and recommends that setup.
For what it's worth, my engine with a 22x12 was pushing dangerously close to hitting 7,000rpm - I stopped after I saw a peak of 6,900 and something briefly!
I don't pin the throttle for more than a small handful of seconds at most, so not too worried. Mostly fly at half throttle or so; and it seems to cope well anyhow without overheating, as well as I am checking valve clearance regularly. The rated RPM is on the ground as well don't forget... David Payne of Horizon runs his off onboard glow, with a 22x12 Mejzlik, pushing 6,250 on the ground and recommends that setup.
For what it's worth, my engine with a 22x12 was pushing dangerously close to hitting 7,000rpm - I stopped after I saw a peak of 6,900 and something briefly!