UMS Evolution Radial Care and Operation
#1727
Join Date: Mar 2006
Location: East Aurora,
NY
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My UMS 9-99 seems to have very little compression when I turn the prop over. It is very smooth but offers little resistance to turning over. When I put it away last fall I went thru my usual routine of injecting after run oil and air tool oil as I did after each flying session. As I recall it had more compression than it seems to have now. As I get ready for the next flying season I would like to address any problems early on.
John
John
#1728
My Feedback: (207)
My UMS 9-99 seems to have very little compression when I turn the prop over. It is very smooth but offers little resistance to turning over. When I put it away last fall I went thru my usual routine of injecting after run oil and air tool oil as I did after each flying session. As I recall it had more compression than it seems to have now. As I get ready for the next flying season I would like to address any problems early on.
John
John
#1729
My Feedback: (207)
Hey Chroner, just curious how many hours have you been able to log on the 7-77 at those RPM's. I have always kept mine under 4600-4800 on the ground.
Are you saying that you run 6k steady on the ground? Wondering if I have been over proping mine. I have 4-5hrs on one and 1-2 on the other. I seem to have plenty of power and speed flying 32-34lb planes.
Are you saying that you run 6k steady on the ground? Wondering if I have been over proping mine. I have 4-5hrs on one and 1-2 on the other. I seem to have plenty of power and speed flying 32-34lb planes.
#1730
Hi guys. I've read through most of this thread but could use a couple tips. I picked up a used 35cc Evo for a steal. It is already broken in. It's going in a Seagull Bucker Youngmeister bipe.
-What's the easiest fuel option? Gallon of 15% pink + a gallon of methanol (7.5% nitro, 9%oil)?
-What's the best after-run oil?
-Manua says fuel consumption is 1oz per min...I'm thinking a 12 oz tank.
Thanks!
-What's the easiest fuel option? Gallon of 15% pink + a gallon of methanol (7.5% nitro, 9%oil)?
-What's the best after-run oil?
-Manua says fuel consumption is 1oz per min...I'm thinking a 12 oz tank.
Thanks!
#1731
Well I already answered one question and ordered a few gallons from Ritches Brew.
-So what machine oil? Something in a precision dispenser would be nice.
-12 oz tank enough?
-And I'm reading that onboard glow isn't necessary. Can I run something external that I can unplug once it is running?
-So what machine oil? Something in a precision dispenser would be nice.
-12 oz tank enough?
-And I'm reading that onboard glow isn't necessary. Can I run something external that I can unplug once it is running?
#1732
Thread Starter
My Feedback: (62)
On the 9-99, you are turning a 100cc prop against 11cc cylinder,one at a time. Will seem like low compression. Best oil is air tool oil. Running with no on-board glow is possible but good tuning is required. On the 7-35, use more oil with fuel like 10%. It is a delicate engine and do NOT let it run lean. 12 oz is good, these engines should not be run at full throttle constantly. -tom
#1733
Need some help. The glow harness has a positive and negative with two banana plugs. How did you guys mount these? Not sure why they didn't put females on it.
Since mine is already well broken in, I'm not running onboard glow, so I just need to make up a NiCD pack with female banana plugs, right?
Since mine is already well broken in, I'm not running onboard glow, so I just need to make up a NiCD pack with female banana plugs, right?
#1735
Thread Starter
My Feedback: (62)
Pietenpol Sky Scout
Well folks, a milestone with my winter build. I have the frame-up completed on my S2 models Sky Scout with the rare Seidel ST-540. This was a limited edition engine with only 300 made. Think of it as a 5 cylinder version of our 7-77 and 9-99's. The prop is true scale size and pitch. The middle shock portion of the landing gear is not inserted into the hole but will be. The instrument panel is covered with veneer from an in
dividual cigar container.
dividual cigar container.
#1737
Hey Chroner, just curious how many hours have you been able to log on the 7-77 at those RPM's. I have always kept mine under 4600-4800 on the ground.
Are you saying that you run 6k steady on the ground? Wondering if I have been over proping mine. I have 4-5hrs on one and 1-2 on the other. I seem to have plenty of power and speed flying 32-34lb planes.
Are you saying that you run 6k steady on the ground? Wondering if I have been over proping mine. I have 4-5hrs on one and 1-2 on the other. I seem to have plenty of power and speed flying 32-34lb planes.
I've got about 7 hours on mine. Not a huge amount of time, but completely stripped mine recently and looks and runs perfectly fine for me. I think really the main concern of revving this engine too high is the chance of losing a pushrod. You have to adjust them carefully IMO. The internals of the engine (bearings, and materials) are high enough quality that revving up to 7,000rpm won't do any damage that's for sure... the bearings are very beefy as is the overall construction of the moving parts.
Just keep an eye on pushrods for any 'chips' and check valve lash. Again I don't think you'd want under 5,200-5,500 on the ground optimally for the engine from my experience anyhow. The engine's RPM is rated as 6,000 'max' (on the ground) in the manuals. I know the designer of the Hangar 9 60CC Corsair David Payne recommended running a 22x12 at 6,250 rpm approx on the ground as what he's found to be the best combination for the engine (7-77) and plane (posted here on RCU in the thread for the plane near the beginning)... and the 22x12 is one of the recommended props in the instructions as well.
I just don't think (as with any more expensive 4 stroke model radial engine you can buy) if you're after longevity you want to pin the throttle at full all the time. I do it for very short bursts while flying and on takeoff But having that reserve and a wider RPM range to work with when flying can be a good thing to have sometimes.
Last edited by chorner; 02-18-2016 at 12:31 PM.
#1738
Junior Member
Join Date: Jan 2009
Location: arad, ROMANIA
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Hello Guys ... i just came in the possession of an 7-77
Question is it a problem if i fly it with an 3x20x10 i see recommended is 3x22x10 but i just have a beautiful scale 3x20x10 already
Question is it a problem if i fly it with an 3x20x10 i see recommended is 3x22x10 but i just have a beautiful scale 3x20x10 already
#1739
Technically it should work just fine. To move up to a three blade you need to bump one catagory or the other down one step, so, moving from a 22 to a 20 should do it.
Let the real world application and trials began
Let the real world application and trials began
#1742
Maxam....
May I suggest some cross bracing on the cabane struts, and across the centre section. I've a parasol wing plane ( general western Meteor p 2 s ). And it stiffened up the wing a treat for very little weight gain
May I suggest some cross bracing on the cabane struts, and across the centre section. I've a parasol wing plane ( general western Meteor p 2 s ). And it stiffened up the wing a treat for very little weight gain