WARBIRDRCER

My Feedback: (22)

I hope the following helps in the understanding of the pulse pump grease issue. The first (1st) photo 091 is a front view of the MOKI 250 with the nose case removed. The view shows the gear assembly consisting of the ring gear (timing gear), the two planetary gears, and the center crankshaft drive gear. This gear is actually machined into the crankshaft itself. (See photo) The planetary gear at the bottom of the photo drives the pulse pump connecting rod by an off center concentric lobe.

The second (2nd) photo 1033 shows the pulse pump connecting rod and piston located in its installed position on this lobe.

Photo three (3) photo 092 is the underside of the nose case as removed. Note the amount of grease that has been slung by centrifugal force to the outer radius of the nose case. You can now see how this grease ends up in a position for the pulse pump to allow it to pass by its piston seal to the top side of the piston and out of the tube, and/or the air intake hole in the pump housing. See photo four (4) photo 012 which shows the pulse pump parts layout.

My explanation of why some Powerplants pump more grease than others is dependant on where the grease is slung during initial runs. The more grease distributed to the pulse pump location, the more likely you will pump more grease than an engine which had more of its grease slung to the opposite side of the nose case.

Concerns you may ask? I have only one (1). In the event the intake air hole, or pulse tube become clogged and the grease builds up inside of the pulse pump cylinder to the point of causing a hydraulic lock, (grease will not compress, so the lock occurs when the piston can not complete its upward travel due to the grease, thus causing a stopping of the piston travel in the pump cylinder), then something has to give. So what is the weakest link? The piston connecting rod, or the planetary gear lobe? Who knows, but I surmise either situation will most likely result in an excessive side load to the planetary gear, possibly damaging the gear pin and allowing this gear to bind into the crankshaft gear leading to a catastrophic engine failure.

Fixes you may ask? I suggest the removal of the pulse pump assembly and using the electric fuel pump for fuel distribution. However, the nose case must be removed to accomplish this step. I plan to remove mine during its rebuild I am currently conducting. If you choose not to remove the pump, keep an eye on the pump for clogging. If you have had grease passing in the past, and it stops be cautious. Also track how much grease you are losing. Like a slow drip of an oil leak, it only takes a short time to loose a lot of oil.

hope this info helps some.

didiwatt

My Feedback: (38)

Do you recommend not plugging the outlet of the pump housing when using the electic fuell pump, thus allowing grease blow by?

WARBIRDRCER

My Feedback: (22)

The short answer to your question is do not plug the pump or line.

Explanation:

Because the pump is only designed to pump air pulses to the carburetor to operate the carburetors diaphragm to pump fuel and not designed to pump the grease from the case, I would be reluctant to plug the pulse pump or its pulse tube. This may assist in preventing the pump from a hydraulic lock situation. However, if you are running an electric fuel pump there is no need for a pulse pump, so have the pump assembly removed now, or wait until there is a reason to remove the front nose case.

The reason the electric fuel pump works so well in this installation is the Walbro carb is designed for an engine which provides a stronger pulse to the carb. Although the MOKI’s are engineered very well, the pulse pump is inadequate in providing the required pulse rate and possible pressure. Not to mention the grease passing by the pump’s piston seal and limiting or stopping airflow, this making the electric pump a good choice.

Now with all of that said, some have properly operating pulse pumps, thereby not experiencing what others do.

WARBIRDRCER

My Feedback: (22)

If anyone has used parts, used damaged parts, used servicalbe parts, or a damaged MOKI 150 or 250 please contact me.

Thanks

JRSmith

My Feedback: (47)

I am awaiting my Moki 250 from Vogelsang Aeroscale and wondering if anybody has a file or picture of a mounting template so I can convert it into CAD. I have been through the entire thread and have not found anything. Thanks and take care.

Jason

Vampire

My Feedback: (2)

A thought for Bob (germrb) and others with MUCH more operating experiance than I. I have seen a method used in full scale aviation that may be of help and an alternative to high temp silicone which does not always work, to solve the Exhaust nut loosening problem and I'm curious if anyone has tried this.

It is very simple in nature, it only requires the drilling "ACROSS the FLATS" of the Exhaust Hex Nuts to allow use of SAFETY WIRE.

I have added the link here to Aircraft Spruce web site to better present the tool and procedure. The nuts do not have to be removed from the manifold to perform this drilling. SEE PICTURE.

http://www.aircraftspruce.com/catalog/topages/nutsaftblok.php

Bob, Scott, others, your thoughts are requested and most welcome.

P.S. as a side note here is the most recent progress on my Seversky P-35 (grandfather to the P-47) design / build project for my MOKI-250.

germrb

My Feedback: (3)

Vampire,

First of all, great looking work on the P-35.

Installing safety wire would certainly solve the problem. The jig would make drilling the holes pretty foolproof. The only challenge is having to remove the exhaust manifolds from the engine.

I have had one other thought about sealing the exhaust manifold nuts and that is to use gasket material. I use Permatex "Ultracopper" as gasket material for all my engine/muffler interfaces. It cures to a firm rubber consistency, whcih would retard the effects of vibration. I haven't tried it yet, so its just theory at this point.

Good luck,

goodinmw

Aloha and thanks for this wonderful forum and thread.
I successfully flew my Moki 150 in a Don Smith Kit Corsair last weekend, and this success was at least in part due to the comments and inputs found throughout this thread.
I'm currently still "tuning" the engine, solo prop and airframe and will start posting my lessons learned as I go.
link to the Youtube video:
http://youtu.be/08vW-9vcoug
Mahalo,
Mark

WARBIRDRCER

My Feedback: (22)

Bob and Kerry,

Both are great ideas, and I to have used the same gasket sealer for my exhaust flanges and hardware installations. It handles the vibration and temperatures without fail.

As for the safety wire tool, I am not sure if the flat has enough material to prevent the drilled hole from breaking out into the tube end. I have one disassembled, so I will check and see. If you do this, you will want a minimum of .020 - .025 stainless wire. This can also be purchased through Aircraft Spruce. The reason for this is vibrations may chaff through the wire over time. How do I know this? Well over my 35 years in aviation maintenance I have seen it more than once. Another concern is this wire has been known to chaff its way through the item it is securing. In this case you would need to drill an extra flat while it is disassembled for future use.

The engine I acquired has set screws installed. See the photo for details. None were loose during disassembly, so I guess it works.

Hope this helps.

Vampire

My Feedback: (2)

Thanks Bob.

Progress on the P-35 is slow but steady. It typically takes 10 > 12 months from design to test flight, so I pretty much on schedule.

@ $35.00 for the SAF-T-LOK drill guide, I will purchase and see how it works and will report back on some test drills before moving forward with the drilling of the MOKI exhaust nuts.

Take care all,

WARBIRDRCER

My Feedback: (22)

Aloha to you too,

Great looking plane and flight. Say a friend of mine has talked about you guys and your warbirds. His name is Jim and flys a giant scale Jenny. I think he attended an event with your club at Ford Island last year. Anyhow, thanks for the great videos.

Flight Leader
WARBIRDS OVER OKLAHOMA

Vampire

My Feedback: (2)

Warbirdrcer,

Thanks for your feedback. Set screws are yet another way to get-er-done.

GaryM

My Feedback: (14)

Can you give us more info such as weight, prop size and pitch etc.

Beautiful landing by the way.

goodinmw

Sure!
The Airframe is from Precision Cut Kits from Don Smith plans,
The all up dry weight ready to fly is 47lb
The three blade solo propeller is 26in diameter. I had the pitch dialed way back to about 5 for these initial flights (you can hear the tips singing a bit during the runup).
I intend to start increasing the pitch as I get the engine dialed in, and get used to the plane.
Radio gear is all Futaba, 14MZ radio, 10 servos, and a smartfly system with two 4200mAh NiMH battery packs.
Robarts landing gear, gear doors operated via an air switch acutated by folding gear strut (just like full scale)
Cowl flaps are set up for functionality, though I chose at this point not to add the weight of another servo (maybe later)
Image shows mount from underside and without cowl- Note this is the same mount I used in the plane but not the same airframe, mount designed to hold the cowl w/o any exterior fasteners.

jairaksinen

Ihave rather interesting feature in my Moki 250. The top cylinder is everytime the coldest one. the hottest ones are no. 2 and 4. the hottest ones are somewhere 115-120 °C and the top one is 110 °C give or take. The prop is soloprop 30x16 threeblade. Any ideas why would the top cylinder be the coldest one?

Here is video of the plane.

http://www.youtube.com/watch?v=giLwyanksBU

wojtek

My Feedback: (73)

I have a 250 coming my way, and though i have experience with pretty much any other engines out there from glo through turbine, this will be my first radial... I ordered the turbulator and pump for this engine, and its going in a CARF p-47. Soo .... should i disconnect the pulse pump all together on a new install ? Im figuring i might as well take apart the engine to do this before its in the airplane ... ??

thanks for any further info on this [8D]


Voy

germrb

My Feedback: (3)

Voy,

If you are going to install the pump, disconnect the pulse line completely. Don't block the pulse pump!! It must be free to expel air (and grease).

Enjoy,

TJPro351

My Feedback: (8)

Bob,
I understand not blocking the pulse pump side to let air/grease escape but what about the carb side? Do you simply disconnect from the festo fitting or do you cut the tube and cap it off on carb side and leave other side open?
Thanks,
Tim

germrb

My Feedback: (3)

Tim,

Just pull off the tube at the carb and leave it open; just like a regular carb arrangment.

WARBIRDRCER

My Feedback: (22)

Voy,

I agree with Bob on both accounts.

goodinmw

Aloha,
Regarding cold #3 cylinders due to a rich fuel mixure-
Has anyone ever consider putting an air bleed screw on the intake pipe feeding the "rich" cylinder to lean it out?
Seems to me with a 4 stroke the fue/air is drawn into the cylinder on the piston downstroke, a bleed air could be adjusted and drawn in to lean the mixture on the offending cylinder.
What's not clear to me, since I've not in usual engineer-in-me fashion torn the engine apart to see how it works, is their an air plenum feeding the other cylinders such that their intake strokes would also draw in air on their intake strokes. If not great, if so this would still seem to be a possible solution, just more experimenting to get the right hole size and flow rate.
Something like robart's bleed screw on their adjustable landing gear valve might do the trick. If someone has an extra intake tube for a Moki 150 they'd be willing to sell, I'm game to experiment!
Thoughts?
Mark

WARBIRDRCER

My Feedback: (22)

Mark,

I would recommend not creating any induction leaks on an engine. Induction leaks are a cause of burnt exhaust valves. Also the way this engine is designed would not allow you to control the induction leakage to a single cylinder. The photos show after the fuel air mixture passes through the carburetor and intake tube, it enters a common area inside of the crankcase behind the Master Rod and Articulating rods. As an intake valve opens it pulls its fuel air charge from this area. Creating a leak would have a hole in a straw effect and most likely run the cylinder extremely lean. This type of leaning could lead to not only burnt valves, but damaged piston, rings, and cylinder walls.

I believe in an earlier thread you stated the engine runs fine at first, and then starts to fail as the number of flights increase. This included even after the engine has cooled.

If you are having cold cylinder problems in this situation, you could first swap the plugs from the hottest and coldest cylinders to see if the problem prosiest. If so, I would try one of two things next. Assuming you have an adequate spark, and no excessive resistance in the plug lead, try a CM6 Type Iridium plug in that cylinder. You may find it under the NGK Rcexl brand. They can resist fouling when other plugs of the same heat range may not. The other option, or if this one fails is to move to a one step hotter plug. With NGK this means a lower number plug (means hotter) if available in NGK. The reason for trying a hotter plug in a cylinder that fouls a plug is to prevent the build up of combustion deposits which cause fouling. The side note to heat ranges is the heat range is the length of time it takes a plug to transfer combustion chamber heat to the cylinder head.

goodinmw

Replying to request for cowl flap info:
(probably belongs in another forum though)

Short video gives you an idea of how it works, though on the plane the
kevlar line is drawn through the firewall to a sail winch servo in the
fuselage

http://www.youtube.com/watch?v=2XV4dHoXnCA

Pic...827(2) below shows the inside of the flaps- the outside flaps are cut from
the cowl, the inside flaps are from 1/32 ply.
I used torsion springs from Gardner Spring (PN: GT2814018-MR) to spring the
flaps open.
I bonded short lengths of tube to the outer flaps and then ran a line of
Kevlar (from an old aerobatic kite) through them so that when tensioned, it
would pull the flaps closed- I particularly like this system since if the
Kevlar failed the cowl flaps would fail open.

The Kevlar line was routed through a brass grommet lined hole in the
firewall to a servo winch in the fuselage (Pic DSCN3898).
This pic also shows my engine mount- distributes the load out across the
firewall closer to the skin and provides mount for cowl flanges.

Pic...5726(5) shows the cowl mount flange that the cowl mount block snug
fits over and is retained by the bungee cord. This way I had no external
screws on the cowl. I probably don't need the bungee, but I feel better
with it.

Mark

goodinmw

Thanks Warbirdrcer!
It was just a thought.
I don't have room for the velocity stack, and am not convinced on the turbulator I've read about, plus I want to try eveything else before I start taking anything apart.

Thanks for the internal pictures, helps me understand a lot.
I'll try your recommendations, especially the CM6 Type Iridium plug.

I'm also going to adjust the idle a bit higher and leaner as recomended in one of the other posts I read over the last couple days. (after cleaning or replacing the plug of course).

Mahalo
Mark

goodinmw

OK, thinking a bit more- (beer in hand)
and definately not an engine expert.

Aren't the burnt exhaust valves due to an overlean mixture and hot cylinder?
My current condition is an over rich mixture, leaning it a bit seems like it would move the mixture in the right direction.

I'm also not convinced the bleed air would significantly impact the other cylinders- since the #3 cylinder intake valve is closed there should be no back flow in the #3 intake tube other than the small volume drawn in the bleed hole. The intake tube is about 1/2in dia and 6 in long which I calc to about 20cc, or 2/3rds of the next mixture charge, so I don't think the leakage into #3 tube (assuming hole closer to valve than crankcase) will reach into the other cylinders.

Thoughts?

(I'm still going to try your recommendations first!)

Mark