UMS Evolution Radial Care and Operation
08-25-2015, 04:58 AM
#1601
Yes the 16% nitro will have a strong effect on gasoline. You are asking a lot from your engine. If it holds up well, this will demonstrate these are good strong engines! Someone sure screwed up assembling your other engine without O-rings. I would be upset too! I fly Moki's too and we are careful to keep ground rpms around 4000. There are guys screaming their Moki's and some are blowing them to pieces! -Tom
08-25-2015, 06:18 AM
#1602
I would love to own a Moki 
I think I'd be much less harsh on the engine in general owning one of those, considering the price premium especially. The cost of these 7-77 radials is a little more reasonable in terms of taking a bit of risk; for me anyhow. I've not seen an issue yet, and seems to be very reliable run after run. I don't generally fly it very hard however, and at most 4-5 times an outing at 8 or 9 minute flights each. Quick bursts of full throttle for a nice low pass, then more than enough speed and pull around half throttle. Without a doubt, my best running engine after all the time taken to learn the ins and outs, and converting to CDI with high quality plugs.
So far she seems solidly built. Nothing improved CDI ignition timing, careful valve adjustment and a bit of castor to coat the internals won't smooth over haha I'll be sure to post here if/when the engine self destructs.
I think I'd be much less harsh on the engine in general owning one of those, considering the price premium especially. The cost of these 7-77 radials is a little more reasonable in terms of taking a bit of risk; for me anyhow. I've not seen an issue yet, and seems to be very reliable run after run. I don't generally fly it very hard however, and at most 4-5 times an outing at 8 or 9 minute flights each. Quick bursts of full throttle for a nice low pass, then more than enough speed and pull around half throttle. Without a doubt, my best running engine after all the time taken to learn the ins and outs, and converting to CDI with high quality plugs. So far she seems solidly built. Nothing improved CDI ignition timing, careful valve adjustment and a bit of castor to coat the internals won't smooth over
haha I'll be sure to post here if/when the engine self destructs.
08-25-2015, 10:00 AM
#1604
Definitely. The only thing I would say about the OS is that from what I can gather, rusting is less an issue, and it is very well built. Better than this engine without a doubt in all aspects, and the carb especially. I would hazard a guess, that with the OS on CDI you'd have very similar performance numbers to what I'm seeing now with even less worry of it self destructing at 7,000 rpm
For the money, this is an excellent engine however. The cast heads are a bit soft, but the workmanship on the rest of it and the beefiness of the bearings and internals in general, should mean it will last a good while without and major issue that I can see anyhow.
P.S - the Mejzlik has a prop constant of 1.18 and 5.41 HP with 31.66lbs of static thrust. I have a spreadsheet I found that has a whole host of info/calculations; can't remember where I found it exactly but good to know its numbers are similar to yours.
For the money, this is an excellent engine however. The cast heads are a bit soft, but the workmanship on the rest of it and the beefiness of the bearings and internals in general, should mean it will last a good while without and major issue that I can see anyhow.
P.S - the Mejzlik has a prop constant of 1.18 and 5.41 HP with 31.66lbs of static thrust. I have a spreadsheet I found that has a whole host of info/calculations; can't remember where I found it exactly but good to know its numbers are similar to yours.
Last edited by chorner; 08-25-2015 at 10:13 AM.
09-18-2015, 04:42 AM
#1607
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Hi all
I have a slightly "different" planned use for a 260cc Evolution radial engine.
I am building a replica 1910's US board track racer (effectively a bicycle with a motor) and plan to use a 260cc Evolution radial engine. However although the engine is rated at 15hp which is more than sufficient for the job, I have concerns about whether it is sufficiently robust for the task.
Obviously the stress on the connecting rods, crank and output shaft will be geater given that the drive via chain drive and centrifugal clutch to a wheel running on the road - with all the related torque and backlash build-ups in the drive system that wouldn't be pressent with just a propellar attached.
The bike is not going to be ridden very hard (or very much) and will be mainly used as a "paddock" bike for getting around the paddock at the historic race meetings I go to and perhaps for the odd trip to the coffee shop.
Hence I was wondering what you guys that have a great deal of experience in these think of this idea?
The one area that I have concerns about is that the output shaft of the 260cc engine seems to only be 12mm in diameter. Does this mean that the sizing of the entire crankshaft, etc. is of this sort of gauge, or is the output shaft just stepped down for a standard propellar to fit? Also, assuming thatthe crank sizing is larger than 12mm within the engine, is there anyway of upgrading this element of the engine?
I also have a few other questions:
·Can the exhaust collector ring go either side ofthe cylinders? I see that the Siedel had the engines had the collector ring onthe propeller side and Evolution seems to have them on the other side – I wouldprefer to mount the exhaust collector on the propeller side of the cylinders ifpossible.
·Can your carburettor be replaced by a larger andmore sophisticated one, and if so what would you recommend?
·If the tank is mounted above the engine can thevacuum driven fuel pump be removed and gravity used to supply fuel to theengine?
Finally, does anyone have more detailed photographs / engineering drawings(internal and external) so that I can start thinking about the mounting of theengine and how to relocate the electronic ignition system, etc.?
Thanks for the help!!!
Regards
Dave
I have a slightly "different" planned use for a 260cc Evolution radial engine.
I am building a replica 1910's US board track racer (effectively a bicycle with a motor) and plan to use a 260cc Evolution radial engine. However although the engine is rated at 15hp which is more than sufficient for the job, I have concerns about whether it is sufficiently robust for the task.
Obviously the stress on the connecting rods, crank and output shaft will be geater given that the drive via chain drive and centrifugal clutch to a wheel running on the road - with all the related torque and backlash build-ups in the drive system that wouldn't be pressent with just a propellar attached.
The bike is not going to be ridden very hard (or very much) and will be mainly used as a "paddock" bike for getting around the paddock at the historic race meetings I go to and perhaps for the odd trip to the coffee shop.
Hence I was wondering what you guys that have a great deal of experience in these think of this idea?
The one area that I have concerns about is that the output shaft of the 260cc engine seems to only be 12mm in diameter. Does this mean that the sizing of the entire crankshaft, etc. is of this sort of gauge, or is the output shaft just stepped down for a standard propellar to fit? Also, assuming thatthe crank sizing is larger than 12mm within the engine, is there anyway of upgrading this element of the engine?
I also have a few other questions:
·Can the exhaust collector ring go either side ofthe cylinders? I see that the Siedel had the engines had the collector ring onthe propeller side and Evolution seems to have them on the other side – I wouldprefer to mount the exhaust collector on the propeller side of the cylinders ifpossible.
·Can your carburettor be replaced by a larger andmore sophisticated one, and if so what would you recommend?
·If the tank is mounted above the engine can thevacuum driven fuel pump be removed and gravity used to supply fuel to theengine?
Finally, does anyone have more detailed photographs / engineering drawings(internal and external) so that I can start thinking about the mounting of theengine and how to relocate the electronic ignition system, etc.?
Thanks for the help!!!
Regards
Dave
09-18-2015, 05:17 AM
#1608
Dave, There is a point you did not mention. This is an air cooled engine that demands high velocity airflow over the cylinders. You would need to build a shrouded fan system to cool the cylinders otherwise it would overheat in less than a minute. You can view youtube where someone put a Sanye 5 cylinder radial in a moped with some success due to it being a glow engine which runs far cooler. He had a fan system as well. There would be less stress to the engine if you used rubber coupling or a rubber damped clutch. -Tom
09-18-2015, 05:28 AM
#1609
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Tom
Thanks for the info.
I was initially thinking of running a fan within the drive sproket to help cool the cylinders, but it seemed that these engines run quite cool and I was hoping that with the positioning of the motor in the open airstream that this would be suffiecient - perhaps not.
Obviously there are plenty of simpler and more "logical" engine choices, but the main reason for using a radial engine is the looks and I don't want to loose that by shouding the engine too much.
The rubber coupling is a great idea - yet another topic to research!
Thanks
Dave
PS I am up to about page 28 of thsi fantastic thread - thanks to all the participants for sharing their experiences, ideas and advice!
EDIT: Finished the entire thread - what a great source of knowledge - thanks
Thanks for the info.
I was initially thinking of running a fan within the drive sproket to help cool the cylinders, but it seemed that these engines run quite cool and I was hoping that with the positioning of the motor in the open airstream that this would be suffiecient - perhaps not.
Obviously there are plenty of simpler and more "logical" engine choices, but the main reason for using a radial engine is the looks and I don't want to loose that by shouding the engine too much.
The rubber coupling is a great idea - yet another topic to research!
Thanks
Dave
PS I am up to about page 28 of thsi fantastic thread - thanks to all the participants for sharing their experiences, ideas and advice!
EDIT: Finished the entire thread - what a great source of knowledge - thanks
Last edited by deimh; 09-19-2015 at 11:09 AM.
10-06-2015, 04:46 AM
#1610
I have decided not to tolerate the carbs supplied on the 777 and 999 anymore. I have ordered 3 of the OS FF240/320 Pegasus carbs and will turn them down to a dimension enabling me to make an adapter for these engines. I did this to a Saito 325 radial resulting in far better operation. The supplied carbs will not go rich enough unless the idle is set overly rich to compensate. Too bad the OS carbs are backordered right now. They are due this month. -Tom
10-06-2015, 10:27 AM
#1613
I have decided not to tolerate the carbs supplied on the 777 and 999 anymore. I have ordered 3 of the OS FF240/320 Pegasus carbs and will turn them down to a dimension enabling me to make an adapter for these engines. I did this to a Saito 325 radial resulting in far better operation. The supplied carbs will not go rich enough unless the idle is set overly rich to compensate. Too bad the OS carbs are backordered right now. They are due this month. -Tom
10-31-2015, 12:58 PM
#1615
My Feedback: (4)
[QUOTE=Pull Up Now!;12109381]Hmnn that is interesting, I have one of those carbs I took off my Pegasus 320 when I converted it to a Walbro for gasoline operation.[/QUO what did you do to convert your 320 to gas? I have one and was thinking of doing that can you email me instead of talking about this on this thread? [email protected] thanks.
11-07-2015, 12:08 PM
#1623
The adapter
The adapter has been made and yes the carb had to be turned so the insert is long enough. Longer set screws are used which go through the adapter to the carb. The carb was supported with a live center during turning.
The flange is 1 mm thick. The installation is complete so I will hopefully run today if it warms up enough.
Last edited by Maxam; 11-08-2015 at 05:08 AM.
11-08-2015, 10:47 AM
#1624
The weather cooperated. Got the engine started with ease. The carb as sent from OS was too lean on the low idle and rich on the top....yes folks too RICH (!) on the top end. After a quick tune in the results are near perfection. Far better midrange, and the top end; 5500 on a 24x12 prop. My very conservative prop power calculator from Germany indicated 4.45 Hp! This is unreal. We are in DA -50 territory but with a huge prop. I think I had better go to a 25x12. Very careful observation; the last bit of throttle had no change in RPM. The carb is now set to 85-90% open with perfect throttle response. Excellent transition everywhere. If you sense I am thrilled you are correct! Expectations are exceeded. I am using 10% oil and 8% nitro.. -Tom
11-08-2015, 11:08 AM
#1625
I forgot to mention, am sure many of you noticed the slop in the throttle linkage. I redid that too and it will adapt to the OS carb. I have no idea ho the italics got there. I used Astro flights prop calculator and it indicated 4.67 Hp. That is .86 Hp/lb. Wow a 3D radial!
