Author Topic: Double Star 40 plain bearing shaft (Read 4291 times)

Chuck Feldman · « **on:** November 08, 2007, 11:45:53 AM »

Is there an answer to this problem? LOL please don't say get a fox or an OS etc. LOL I know that its funny but I am trying solve this problem for a friend. Sig 10% nitro, 20% oil half and half 11/5 zinger prop Sig 3 plug. The model will take off with good engine setting and fly through about 1/2 of the tank. Then it goes lean and stays there for the remainder of the flight. If we fly it richer it of course cannot fly the pattern but it will hold the needle setting. If you close the needle to get the desired run it never gets there and goes into the lean run as above. I understand there are other people who have similar problems with this engine. Perhaps there is a solution?

Chuck Feldman

Bill Little · « **Reply #1 on:** November 08, 2007, 11:53:26 AM »

Hi Chuck,

Tom told me to use two or three extra head shims if I was going to run ANY nitro. The engine is set up for FAI fuel and is overcompressed in stock form.

I have 3 or 4 (??) head shims in the engine, and opened up the venturi to about 290-295 (have seen as big as 300). The *stock* throat area is less than a Stock Fox 35!!

On 5% and 10% Sig, it runs like a true 40 now.

Ron King · « **Reply #2 on:** November 08, 2007, 12:30:15 PM »

Steve Fitton and I fought this same problem a year or so ago with our DS 40s.

You could set your watch by mine - it would fly great until the Horizontal Square Eight. Then it would start working hard through that maneuver and never settle down for the rest of the flight. I did everything Bill suggested (more head shims, bigger venturi) and it helped - but I'm still not convinced that I solved the problem.

Steve changed his needle valve assembly to a small PA unit and his engine was running great at Huntersville last month. I believe he also went back to a smaller venturi. I hope he comes on here and tells us exactly what he did.

Ron

Chuck Feldman · « **Reply #3 on:** November 08, 2007, 02:43:07 PM »

Bill, Ron & Ty,

Thank you for your respounces. I am going to continue to read all of them and I think we will get an answer to this. Interesting that Tom Dixon has finally come out with some things to change. Tomorrow when we fly we will be trying a different needle vale assembly. Why? I have a theory that the the problem is actual the temperature effect on the needle valve assembly. About midway in the run as the heat is building the assembly gets changed and the result is the lean run. I'll of course let you know how well this works. I'll also see now many head shims are in use. This is a fine engine and I have seen them perform some outstanding flights. The running problems in my opinion are far to common and require lots of testing. Perhaps there is a basic problem and once we find it everyone can do the fix.

Chuck

Kim Mortimore · « **Reply #4 on:** November 08, 2007, 08:45:58 PM »

I have one that runs very well, and another that is still tight as a drum after 2 hours on the bench. It will quit in the middle of a run for no obvious reason. I have heard that the crank/bushing fit is excessively tight on some of them, and I suspect that may be the problem with mine.

Phil Cartier has an interesting piece in his Combat column (latest issue of Flying Models) about an engine with a tight bushing that perked up after he honed it using a piece of 1000 grit sandpaper stuck into a slot in the end of a short piece of dowel mounted in a drill. I'm curious if it might also work just to use the crankshaft itself, with rubbing compound, or maybe an abrasive tooth polish, like we used to use on pistons/cylinders back in the old iron piston days. A few layers of duct tape (Nature's all-purpose tool) or electrical tape on the threads of the crank to protect them from the clamping of the drill.

Kim

Larry Lindburg · « **Reply #5 on:** November 08, 2007, 08:53:19 PM »

This is what works for me on my ARF Nobler with a DS 40 Classic plain bearing engine: 2 head shims, .312 venturi, Sig Champion 10 % fuel, 11-6 Graupner propeller, Sig R/C plug. I also had the lean runs mid-flight. Russ Gifford thought the engine was not broken in enough. And sure enough, the lean runs stopped after a handful more flights. It's really a sweet 4-2-4 run now. Larry Lindburg

Mark Scarborough · « **Reply #6 on:** November 08, 2007, 09:17:02 PM »

cant speak for the DS but in my experience,, (NOT an engine guru, just play one lol,, thats a joke son) when an engine leans midflight a lot of times you can fix that by just adding a couple more oz of castor to your fuel. FWIW I have reached that point on several engines and other peoples engines too.

Steve Fitton · « **Reply #7 on:** November 09, 2007, 06:40:24 AM »

More later, but the short version is the PA nva totally cured mine from all the above funnies. It totally rocks now and will hold any setting I want, rich or lean.

Steve Fitton · « **Reply #8 on:** November 09, 2007, 08:14:01 AM »

Mine ran away EXACTLY as Ron King described, and even running a bigger venturi did not completely cure the problem.

A couple of buddies of mine had hounded me for about a year to try the PA nva, and, having worked extensively with Dixon on sorting the problem out to no avail, I tried the nva suggestion and found it to be a total cure. I was even able to go back to the stock venturi, had more power, could run the engine richer or leaner than I did before, and could hold the needle setting all flight. I could also go back to a normal muffler instead of the horrifically loud tongue muffler with all the holes drilled way out.

Not every DS responds this way-I have ,(well, had...)a DS 60 BB motor that I ran with the PA and the stock spraybar back to back. The engine ran fine on the DS unit, and ran identically on the PA unit, so there was not really any gain from using the PA nva on that motor.

Dixon's DS 40 in his yellow Pegasus is absolutely stock, I know because I have peeked at it more than once, and watched it fly alot. I discussed the nva trick with Tom after I tried it, and he didn't criticize the choice. He speculated that the stock unit might have gotten something jammed in it (like a brass shaving or solder globule) that was permanantly wedged in there and was restricting fuel flow.

Whatever the case, I'm now quite happy with my DS 40. It works just like it should. Its a tough motor, too, because it survived 100 consecutive lean runaways without damage!

Steve

Russell Shaffer · « **Reply #9 on:** November 09, 2007, 08:51:22 AM »

A person wants to be very, extremely careful lapping on a bushing. The abrasive can imbed in the soft bushing material and then grind the shaft. When parts are lapped, the usual process is to use a very soft lap against the hard part to be lapped. The abrasive does the cutting. If you know an old machinist, ask him about this. You don't want your bushing turned into a hollow grinder.

Chuck Feldman · « **Reply #10 on:** November 09, 2007, 09:29:24 AM »

Steve; Thank you so much for that information. I have been suspect of the needle valve to. We had some success this morning but still no cure. I'll be getting on the phone with Randy to get some needle valves asap. Of course when they come and the cure is working I'll get back on here and let everyone know about it.

Chuck Feldman

Jimmy R. Jacobs · « **Reply #11 on:** November 19, 2007, 08:04:33 PM »

Hi Ty!
I found the same thing with the DS-40 plain bearing shaft I bought off this forum. It may have been yours. I fixed it; it had a couple of things wrong. The head was not sealing properly and the needle valve was set where the hole was to the front, not pointing down and now it runs great. It has a good two four break.
So, if someone has a DS-50 or 54 they can't get to run right and would like to sell, or just has a DS-50 or 54 they would like to sell, I'd be interested in it if the price is right. (Nana says since Grandpa is on a fixed income and can't get a new one.)

-Jimmy Jacobs
Grandpajake 3

Steve Helmick · « **Reply #12 on:** November 21, 2007, 09:38:01 PM »

I'm thinking that the mid-flight crisis is probably a sign of the engine not being fully broken-in. That said, the DS NV assy.'s are suspect. I recall PW struggling with his Saito .72, which was fitted up with a Tom Dixon (DS mfg'd) venturi/manifold. This at the field at Arlington, a field strip job...unusual for Paul. The DS NV assy came out, and a ST NV assy went in, and problem solved. Later, he said he found a burr in the spraybar cross hole. I asked how he fixed it. "Disposed of it", or something to that effect. Could be inspiration for a new event, like "Fox Hurling".
I can't say I have either of my DS .40's running well, having a mole hole take most the outboard wing off the Profile Cavalier a year ago. But I think one will go well on a SIG "Primal (sic) Force" ARF.

Steve

Chuck Feldman · « **Reply #13 on:** November 22, 2007, 09:59:35 AM »

Happy Thanksgiving;

Down here in South Florida we flew this morning. It is a wonderful day.

Great news. We decided to use a Super tiger needle valve assembly as the PA order has not come in yet.

SUCCESS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! All problems with the DS 40 are gone!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

What a good feeling to have this fine engine running in a beautiful 2/4 break for the entire flight. I have no idea what is wrong with the DS 40 Needle valves and do not care, The ones I have are not going to be used. Pass the word far and wide the DS 40 problem is the Needle valve. replace it with a PA or ST.

Thanks to everyone for your help with this issue.

Chuck Feldman Stuart, Florida

Dave Adamisin · « **Reply #14 on:** November 22, 2007, 10:27:09 AM »

I've always had good luck with rotten stone and wd40. I follow the lapping with a crocus cloth polish of the crank journal and a good scrubbing of the bearing with wd40 and a small toothbrush then lots of liquid laundy detergent and hot water. When I'm doing the lapping I make sure to also pull the crank up against the thrust face of the brg. in the crankcase to clean/polish it as well.

Kim Mortimore · « **Reply #15 on:** November 23, 2007, 04:35:38 PM »

Quote from: Dave Adamisin on November 22, 2007, 10:27:09 AM

I've always had good luck with rotten stone and wd40. I follow the lapping with a crocus cloth polish of the crank journal and a good scrubbing of the bearing with wd40 and a small toothbrush then lots of liquid laundy detergent and hot water. When I'm doing the lapping I make sure to also pull the crank up against the thrust face of the brg. in the crankcase to clean/polish it as well.

Dave,
Very interesting. Thanks for the info. I'm not familiar with "rotten stone." Can you explain what that is, and would you like to tell us a little more about the process, such as how to be sure lapping is needed and how to know when to stop (BEFORE it is too late

). You might have the makings of a Stunt News article here, if that's of interest to you.

Kim.

Kim Mortimore · « **Reply #16 on:** November 23, 2007, 06:58:27 PM »

Ty,
The lapping part of the discussion is about tight crank journal/plain bearing fits, rather than piston/cyl. You are so right about not lapping modern aluminum piston/cyl (except possibly experts adjusting TDC pinch--but I think that ain't us--speaking for myself

).

Cheers,
Kim

Steve Fitton · « **Reply #17 on:** November 24, 2007, 05:14:12 AM »

Chuck,
I'm delighted to hear you got your DS working well!!!!!!! Thanks for reporting that an ST NVA worked just as well in this application, it will give people more information to fix their own DS 40s that might be acting up. Now, those of us that "know" the secret to getting the DS 40 to run well can snag the ones people are trying to unload for cheep!

Ron King · « **Reply #18 on:** November 24, 2007, 07:36:22 AM »

Quote from: Steve Fitton on November 24, 2007, 05:14:12 AM

Now, those of us that "know" the secret to getting the DS 40 to run well can snag the ones people are trying to unload for cheap!

The price of all my Double Stars just went up.

My Nobler (and DS 40) just came down off the "retirement wall" and I'll make the NV mod post haste.

Ron

Chuck Feldman · « **Reply #19 on:** November 26, 2007, 01:55:09 PM »

Thanks to you Steve.

Your the one who made the information in the first place.

Once upon a time there where many stunt secrets I am told. The folks on top would not tell them to the lessor fliers. >:DI never talked to a top flier in the old days but I did heard this story many many times.

About the Ds 40. It is a great engine once the problem is corrected. ::)There are some who do not have the problem but all four of my DS 40's have the problem! Well none of mine are stock now they are converted. I hope everyone gets the word and makes the improvement. I will add this. The engine was made to emulate the fox 35. We all know there are fox's and there are foxes. I expect my DS 40's to run like the best foxes out there. To ask them for more is probably an error. I had one on a Cardinal. It was underpowered. I put on a Brodak 40 and it was fine. Brodak 40 seems to emulate the OS MAX S 35. All we can get from the DS 40 is a great run for the proper model and we get to use lighter oil. I like 50/50 and I use 22% sometimes 25%. I HAVE SOME DS NEEDLE VALVES ASSEMBLIES FOR ANYONE WHO WANTS THEM. I'll KEEP THE ENGINES.

Steve good luck with your new "79 model" what ever it may be. Nothing is better than grassroot developments. I am so happy that the Huntersville club has broadened the scope of Stunt. I think we can use grass root development and stop having all the infighting that goes on. Funny I have never heard much about these issues at a contest. It seems to be an internet thing? Chuck of Stuart, Fl.

Steve Fitton · « **Reply #20 on:** November 27, 2007, 08:05:38 AM »

I'm glad its working Chuck.
In point of fact, the NVA switch isn't really my idea. Both Brad Walker and Eric Viglione had been hounding me for about a year prior to my giving in and trying the PA unit. Both of them had anecdotal evidence of the PA (or equivalent) spraybar offering either increased performance and/or correcting specific problems on an engine.

The internet is excellent for arguing and flame wars, but every now and then it is useful for conveying information to alot of people!

Bill Little · « **Reply #21 on:** November 28, 2007, 09:52:52 AM »

Man, I'm happy I'm the Blind Hog. Maybe I just live in a *little* bubble that protects me!

I have not changed the NVA on either of mine, but I have put in the recommended shims and opened up the venturi. This made it a very stable engine which has more power than my BEST Fox 35.

Then, again, none of them touch an Aero Tiger 36........

Phil Bare · « **Reply #22 on:** November 28, 2007, 11:33:34 AM »

Wonder if it has as much power as an old baffle Fox .40....or a Fox .40 RR...

Bill Little · « **Reply #23 on:** November 28, 2007, 11:55:33 AM »

Quote from: Phil Bare on November 28, 2007, 11:33:34 AM

Wonder if it has as much power as an old baffle Fox .40....or a Fox .40 RR...

Hi Brother Phil,

No where did I mention any Fox "40".

Don't think I would even WANT to attempt to use a 40RR in ANY kind of contest stunter!
Now teh "GMA 40" was one of my all time favorite Stnt Engines, but a good bit heavier than the DS. It pulled a little more prop, though. A *good* DS 40 comes very close to the GMA 40, though.

Phil Bare · « **Reply #24 on:** November 30, 2007, 06:50:18 AM »

Brother Big Bear........iffen ya gonna tawk bout a .40, then ya gots ta tawk .40...and the ol GMA .40 would be the standard by which ya gots ta compare...

Oh, and I have an ol RR.40 built on the Rocket case that I think would do well running in a wet two with the appropriate flat pitch prop on it..a real Hoss engine for its vintage...oh, and then ya really gots ta throw a Lew Wollard Silver Fox .40 in just to keep things interestin......an one more thing, my K & B .40s aint zactly duds either...
hmmmmmmmm.........an my ol Irwin .40.......

All engines are great, even them new four hunnert doller PAs and Aero Tigers that I won,t (or can,t) spend that much money for.......BTW, how much ya take for that Ol ratty McCoy RH .40 ya got???/

....Phil Bare

RandySmith · « **Reply #25 on:** November 30, 2007, 02:55:52 PM »

""All engines are great, even them new four hunnert doller PAs and Aero Tigers that I won,t (or can,t) spend that much money for"""

Hello Phil

Thanks for the mention of my engines , However since you still can't resist putting erroneous info out there, In a thread that was *not* about about my engines, but rather DS engines I will correct this for you. Just so there is no confusion.

Aero Tigers have never sold for 400 dollars ................................ they are $239.00
PA 40 REs have never sold for 400.00 dollars .............................. they are $309.95
PA 40 SEs have never sold for 400.00 dollars .............................. they are $309.95
PA 40 Merlin Ultra Lites have never sold for 400.00 dollars ............ they are $309.95
PA 51 REs have never sold for 400.00 dollars .................................. they are $339.95
PA 51 SEs have never sold for 400.00 dollars ............................... they are $339.95
PA 61 REs have never sold for 400.00 dollars .............................. they are $369.95
PA 61 SEs have never sold for 400.00 dollars ...............................they are $369.95
PA 65 REs have never sold for 400.00 dollars ..............................they are $379.95
PA 65 SEs have never sold for 400.00 dollars ...............................they are $379.95
PA 75 REs Merlin series have never sold for 400.00 dollars ..................they are $399.00

I also have many many more engines that I sell from $50.00 to $399.

Hope to see you again soon, but would like to see ya bring an airplane.

Regards
Randy

Phil Bare · « **Reply #26 on:** November 30, 2007, 03:50:39 PM »

Randy, as you should be able to tell, my post to Billy Little was just a bit tounge in cheek....and as for erroneous info, the ONLY (erroneous) info that I have EVER put on the forum was to call your engines four hunnert doller engines instead of three hunnert doller engines..and I do plan on bringing a couple planes to Huntersville next time...and thanks for the price list....Regards, Phil
PS: BTW are you bringing any planes to fly next time??

RandySmith · « **Reply #27 on:** November 30, 2007, 06:41:22 PM »

Hi Phil

Yep I normally do bring a plane, It was just ,This time I had already committed to helping several people with trim and plane-engine setups.
Plus I had one bringing a plane that had not been flown.
You will enjoy flying at Huntersville, as you could see when you were there they put on a great contest. They are really a good group of guys that put that one on.

but Now don't go calling the Aero Tiger a 300 dollar engine and make me post prices again

Randy

Phil Bare · « **Reply #28 on:** December 01, 2007, 06:11:25 AM »

Hi Randy, I did enjoy coming to Huntersville and getting to meet many of the guys that I had only seen online ..... Many great modelers and many fine airplanes.
I also enjoyed our conversation and getting to see your fine products. Your .75 is fantastic and one day when my skill level gets back to the point that I no longer envision it stuck in the pavement, I will try one. My flying airplanes are mostly just beaters that I have been using to get back up to speed, but I do have a few projects going on that will be of a quality that will not embaress me to bring....My business keeps me hopping and so my modeling activities are pretty much (catch as catch can)....but hopefully, I will be able to sneak in enough time to finish a .60 powered Stephans Acro, a Barnstormer, and a Ringmaster 1000, all in various stages of completion...... Regards, Phil
BTW, I am pleased to see that you are taking on the Enya line and hope that it proves to be an assett for you, always fine engines and deserve good representation

Bill Little · « **Reply #29 on:** December 01, 2007, 11:54:20 AM »

Not sure if this is the proper place, but here goes!

I think it is very much worth mentioning that Randy comes to local contests to help pilots, mostly. I feel he even does so to the detriment of his own flying!

Yes, he DOES have his products there and sells some of his wares. BUT, most of his time is spent with people sorting out their airplanes. He even spends a lot of time with this old blind hog. His time spent with Aaron on his new plane was invaluable. To have a pilot as knowledgeable and capable who is so willing to help us who are struggling is well worth noting!

Bill Little <><

EDIT: No, I am not on Randy's payroll!

And I will add, it doesn't matter what plane or engine you have, if you ask, Randy helps. There are more out there like Randy, but lately he has been the most ready to help of any one I know.

Chuck Feldman · « **Reply #30 on:** February 04, 2008, 08:24:25 AM »

Hello Everyone, Well here it is Feb 4th 2008. The man I fly with who has a DS 40 plain bearing with a ST needle valve assembly has finally switched it out to the Randy Smith needle valve assembly. It is an instant cure of the run problems he had experienced. True he was getting better results when he switched to the ST NVA but it was not good everyday? When it was on it was OK. But the new RSNVA has this engine purring like a kitten. So for me this thread is concluded. The RSNVA can and does work a miracle on the DS 40 pb. One more note. I am flying a Smoothie with and OS 35 S max that is ABC. The needle valve is stock OS. I took it out and put in the RSNVA that cures the DS 40. It is amazing how this NVA has smoothed out this engine. I thought it was pretty good before but now it runs so much better. In my opinion the other NVA's suck air through the packing on the NV. This cause problems large in some engines (DS) and not so bad in others. I fully recommend that your try the RSNVA as soon as you can.

Chuck Feldman

Kim Mortimore · « **Reply #31 on:** February 04, 2008, 10:31:38 AM »

Chuck,

Good to hear the fix is so easy! Is there a model # or other identification for this specific NVA to use when ordering from Randy?

Thanks,
Kim Mortimore

Bill Little · « **Reply #32 on:** February 04, 2008, 11:36:24 AM »

Just tell Randy what it's for. I know he has special ones for the Fox 35 (best on the planet!) and two sizes of his *regular* NVA. I cannot see ever buying a different type

Chuck Feldman · « **Reply #33 on:** February 05, 2008, 08:44:27 AM »

I talked to Randy yesterday and ordered NVA's for all my other engines. While I was so pleased with the results with my OS MAX S 35 Nva switch he told me the proper one was even better. I have ordered NVA for these engine
Brodac 40,
La 46,
Ds 40,
Fox 35,
Os max s 35.

I believe like Bill does "there is no other."

Chuck

Bill Little · « **Reply #34 on:** February 05, 2008, 09:49:25 AM »

While I am in no way connected, financially, to Mr. Randy Smith, his keepers are by far the best design out there. That little nylon (or whatever it is) cone in the keeper does not allow the needle to leak air, and keeps the needle setting tight with out using a wrench. I cannot find another NVA that does this...... A vast improvement over the old ST which I thought was the best before these.

Steve Fitton · « **Reply #35 on:** February 05, 2008, 07:15:02 PM »

I think the Randy NVA you need for a DS 40 is just called the "small" needle valve assembly. When I ordered mine from Randy, I was ashamed to admit I was putting it in a DS and just asked him for the small nva. It fit perfectly. Chuck, I'm delighted that the DS you guys were dealing with responded so well. Its a nice little engine when it has a chance to perform correctly and not go beserk!

Phil Spillman · « **Reply #36 on:** March 03, 2008, 06:51:54 PM »

Several years ago I put a DS .40 in my Veco Smoothie. It performed OK but not great. I installed an ST NVA and added a 9.5 X 4.4 APC and went berserk with the change! I really loved that plane flew it even with Mr. Palmer's autograph on it! Its gone now, the wing with the autograph still hangs in my shop, but the DS .40 is still a winner! Try a dose of your Fox fuel 25 to 28% oil of what ever blend you prefer! My guess is that you'll be happy!