reyn3545

I think I'm going to follow Gotz's advise and go back to a fixed pitch propeller. I've got a 32x18 in both Biela and Fiala. The Biela handled the motor well, but the plane didn't seem to have much speed. It is a big bipe with a lot of drag, so It's going to have need to dive to get the speed up.

Maxam

My Feedback: (62)

I am pleased with the SEP 33x16 Gotz got for me. The speed is excellent with my 37% Yak and the pull is strong. Can go straight up. (Moki 215). -Tom

wphilb

My Feedback: (10)

What prop are you using please? I reread all posts and don't see it mentioned? What is the size and approx weight of your La-7?

Whit

kimhey

I am using a biela 26x16 (2 blade), but have ordered a 26x14 (3 blade) as a 3 blade is more scale. I have mounted a rpm telemetry sensor (in addition to the two temp sensors), but have not tested it yet. The airframe is from cymodels/vmi models ( perhaps other names too?), and is fairly well made compared to the price. I peeled off all the covering and glassed everything, and did some minor modifications. Ended up at 20kg AUW. I needed 850 grams/30oz in the nose to balance at my preferred CG. The model is 1:4 scale, with a ws of 96"/250cm. It is not yet finished scale vise, I have some more work to do on it. Finished, I think it will be a fairly good "stand off" scale model.

My Moki is original.....no external pump, turbulator, rainbow ignition or anything....so far.

wphilb

My Feedback: (10)

Thanks, sounds like a good plane!

whit

Maxam

My Feedback: (62)

Kim, From what I heard in your video and your cylinder temps you are set. If you seem to need to tune the engine a lot, the fuel pump will help. I have been flying my 150 a bunch but a fuel pump will be needed. The fuel delivery is too inconsistent. -Tom

JamesPool

My Feedback: (3)

First post here. Have Moki 250 in a 1/3 scale LA-7. I'm fighting overheating problems in spite of what seems to be very adequate entrance (motor is baffled) and exit ports.

I was doing some thermal imaging of the motor running, and I was surprised that that hottest part of the image was the collector ring by a significant amount. In efforts to get heat out of the cowl, I would like to remove the collector ring and direct exhaust each cylinder. Any technical gotchas that anyone can think of?

James

Jaketab

My Feedback: (2)

While on the subject of engine cooling, I have a question also. I'm assembling a plane with a large diameter cowl. It's a Delro Turner W4X with a Moki 250. Because of the large cowl diameter, baffling is out of the question for now.
Question - has any one tried an inner cowl ring that would extend back just over the top of the cylinder heads? The inner ring would be approximate 12 inches diameter and help direct air flow over the cylinder heads and keep it from dispersing into the cowl until past the cylinders. Any thoughts ?????

Thanks - Jaketab

Maxam

My Feedback: (62)

James, you will need to remove 20 nuts to remove the collector ring. all intake tubes will need to be removed. Yes of course the collector ring will be the hottest portion! Now you can wrap it to contain the heat like guys do with their motorcycle exhausts as shown long ago in this thread. Check it out! -Tom

Maxam

My Feedback: (62)

Jaketab, you could make a laminated ring that attaches to the inside front of the cowl about 1/2 inch larger diameter than the opening, extend it back to where the "normal" baffle would be around the engine. Then paint it all black or dark grey to take attention away from it. When you remove the cowl, it all comes off due to being glued to it. I hope that is clearer than mud?! -Tom

Jaketab

My Feedback: (2)

Maxam,

Yes, exactly. That's what I had in mind. Just like a fan shroud. I've already made a test one from cardboard. It will fit very nicely around the inside lip of the cowl.
Will make it from balsa laminated with fiber/epoxy. Just wondering if anyone has done it and what success with cooling.
The cowl has good exit area in the rear. Hoping to get by without baffles. Only one way to find out for sure.

Thanks - Jaketab

kimhey

Was there ever made a video showing how to adjust the valve clearance? I have red the instruction how to do it (some pages back in this thread), but I am not sure I fully understand. A video or instruction with photos would be nice


Rgds,
Kim

Maxam

My Feedback: (62)

Kim, On RCU "evolution radial engine care and maintenance" (my thread) On the first or second page I give an explicit detailed explanation on adjusting valves on a radial engine. It is much easier to do this with the plugs removed so there is no compression to fight. -Tom

wphilb

My Feedback: (10)

Apologies if I'm violating some online rule on cross posting of websites but this is exactly what I did on my N28 build here:

http://www.rcscalebuilder.com/forum/...71&PN=1&TPN=28

http://www.rcscalebuilder.com/forum/...71&PN=1&TPN=28

I made a cardboard template of 1/5 of the ring baffle and then made five copies out of lightweight roofers Aluminum and pop riveted them into a whole ring. I then used Ali clamps to affix the ring to the exhaust tubes so the the ring was held right over the middle of each cylinder. Works quite well!

Also so I believe that Dr Gotz over at Vogelsang Aeroscale sells a laser cut baffle for some of these engines. He's great to deal with so give him a call and see what he has first.

Baffling is not optional in a full cowl installation IMHO.

Cheers,

Whit

kimhey

Thanks Tom, I think I have the courage to check the valves now

wingstrut

Fellas, This was not a Moki, but I made a baffle that directed the air around both sides of the cylinders and over the top of the cylinders then directed it down and out the bottom of the cowl. After taking many temp readings I found that the cylinders were running very cool at every point but the front that was directly hit by the on coming cool air.
What I have come up with is, the air was flowing at a high rate of speed around the cyl's cooling that part, but the front of the cyl's that were hit by the air coming in was not moving hardly at all creating no cooling.
My temp readings were 175 to 180 on all parts of the cyl's except the front of the cyl's that reading was 220 to 225.

This was a test, for my studies, just thought I would mention my results.

As far as the moki in these large cowls I think Jaketab has hit it on the head, I think an inner cowl ring may be a better answer than baffles between the cyls, that way the exhaust ring will not be blocked and will keep the air around the engine at a higher flow rate. I like the idea enough I think I will try that in my Waco.

elckar69

My Feedback: (1)

Hello,

I just got my new Moki 300cc 5 cylinders, not much information in regards to propeller size, only states a 34x18 which is very hard to find: however, is there anyway to find what is the prop's size range for this engine?

Regards,

Elckar

Jaketab

My Feedback: (2)

Whit and Wingstrut,

Thanks for the input. It's a very large cowl and the diameter of the baffle would have to be increased greatly. When I do the roll out, I'll ground test the engine with and without (will call it a shroud ring) and post the temperature results. I'll calculate the entrance and exit area and add louvers if required. Attached pic showing the cowl exit area.

Wingstrut,

Hope you can post the results for your Waco.

Thanks - Jaketab

wingstrut

Jaketab, I looked at your cowl again, I think you need to reduce the air intake to get that engine to cool properly.
What is going to happen is the air will enter the large opening in the cowl and basically stop, it will exit only as fast as the exit opening will allow.
You need to reduce the intake opening to allow the exit to remove more air that is coming in in order to get a flow over the cyl's.
That is basically what happened in my case, my baffled engine was fine it was the large open intake in the cowl that was the problem, I am going to reduce the air coming into the cowl as to create a higher rate of flow.
I still like your idea of a cowl ring to keep the air around the engine. Maybe a cowl ring and baffles would be the answer. We need an airflow engineer.
It will be a while before I can post the results as I am rebuilding my 1/3 pup, I hit a tree while flying in the fog, by the way that tree is no longer a threat.

Jaketab, May I ask what oil are you using in your Moki, I am having a problem with Amsoil, the exhaust residue is coming out black as paint, that tells me that the oil is not holding up to the temperature and is burning, I'm having this same results in all my engines. Thanks .............Ron

wphilb

My Feedback: (10)

I know I wasn't the one asked but consider Redline high temp motorcycle oil, is twitched over to that and really like it in my Mokis


Whit

Jaketab

My Feedback: (2)

Ron,

You may indeed be correct. Rough calculation. Air entrance = 95 sq. in. Exit area = 65 sq. in.
I'm using Stihl Ultra oil at 45/1 with 1 oz of Seafoam per gallon - good results. Can't speak the gospel, but I understand that this oil is formulated for the Stihl 4 stroke engines.

Jaketab

wingstrut

Thanks Whit and Jaketab, I appreciate you letting me know what you are using also, especially if it is working, I have been using Amsoil Interceptor @ 40 to 1 with 1 ounce Seafoam per gal. regular 86 octane gas. I was mainly concerned about the jet black oil coming out the exhaust, I can understand a little bit, but this is excessive.
This is happening on all my engines not just the Moki, that is why I'm suspecting the oil is the culprit.

nine o nine

My Feedback: (1)

I fully agree about reducing the intake area and enlarging the exit for better cooling....1 to 3 at least. Not only that but directing the airflow around the cylinder fins rather than AT them if possible. Whenever you may get a chance to look at the cowl baffeling on a full scale plane, say a C152 or 172 you'll see that fully half of the horizontal openings are covered with a diversion baffle that directs cooling over the top of the engine and then is sucked out of a large bottom opening at the rear of the cowl with a shaped airflow affair that sucks heated air out. Thhe high powered Piper aircraft have reduced cowl inlets to small circular holes....
Mitch no baffles on my 1/3d Waco but the cowl opening is not much bigger than the width of the engine but the open rear has significantly more area.

shaked israel

another good fligth with moki 250 at show event in israel. so much Satisfaction and Beauty

https://www.youtube.com/watch?v=90G5icIVwLE

ForcesR

Elckar; what size and model aircraft is your Moki 300cc being installed in? Hopefully it will be a "Warbird"!!!