Author Topic: Double Star .40 (Read 4426 times)

Dick Fowler · « **Reply #1 on:** April 03, 2007, 08:32:34 AM »

That seems like a rather large venturi for a .40 displacement engine. Is the spraybar through the venturi? I usually don't like anything much beyond .270" with a through the center spraybar. Fuel draw suffers.

Marvin Denny · « **Reply #2 on:** April 03, 2007, 10:34:03 AM »

Ty, It sounds like one of two possibilities. Too high of compression first. Try adding a couple of head gaskets. Second, an air leak somewhere ---fuel tubing, --- leak around one or both ends of the needlebody---air leak around the venturi to case ---or backplate gasket leak. A third, though unlikely, possibility, engine overheating for some reason.

You might try adding a tad of oil to a single tank of fuel to check that possibility too. don't need to be very accurate for the test, but if it does in fact make a difference,then carefully make additions to determine the needed amount.
Bigiron

bruce malm · « **Reply #3 on:** April 03, 2007, 11:27:13 AM »

I got a DS 40 to put in the cardinal Evolution I picked up, it's now in an ARF Smoothie. It was used a little By Tom Dixon. The thing runs beautiful but a little less power. Tom does recommend to not use more than 22% oil as it tends to cool the engine too much. I have been using Powermaster 10/22. This one had an.008 and a .020 head gasket when I got it. I pulled the .020 and put in.010 but still seems a little weak. I have made up some fuel using 18/10 PM and it is now 20 % oil and about 11% nitro. I will try it again this weekend. The Venturi is about .285. I will try to get some made up to about .300 for experimentation to get more power. But I have a feeling that too much oil is causing most of your problem and maybe a slightly too large venturi.

Bruce

Steve Fitton · « **Reply #4 on:** April 03, 2007, 04:56:32 PM »

Just for starters, thats way too much oil, and not enough head shims, for that fuel/motor. The instructions supplied with the engine indicate 20% half and half as the max lube, and in fact I run mine on Powermaster 18% lube. On mine I run either three or four 0.010 head shims and turn a Powerpoint 11x6 prop with a venturi the same size as yours.

Steve

Walter Hicks · « **Reply #5 on:** April 03, 2007, 05:59:45 PM »

Double Star .40 is does not like CASTOR oil. Use Powermaster 10% with 18% oil add some Klotz or Aero one .

Make sure you have a hot glow plug. The Ukranian engines have different metalurgy and do not need all the oil we are

used to using. I had a DS and kept adding castor until it would not hardly run.. We found out the hard way after

selling most of them how to run them. I have several friends that use this combo and have 0 problems only very

consistant runs. They are not high RPM engines either use pitch 6" or more!

Walter Hicks · « **Reply #6 on:** April 03, 2007, 06:02:37 PM »

Ty,

I will buy it if you dont want it!!!! W Hicks Powermaster 10/22 as stated earlier will probably work.

Larry Renger · « **Reply #7 on:** April 03, 2007, 06:41:41 PM »

I added one .010 head shim to mine, per Tom D's instructions, run 15% 11/11 oil fuel and an 11x5 prop (currently the gorgeous new ones from Eric Rule). It has a Scott Dinger muffler and a Hayes 4 oz clunk tank rigged as uniflo (no muffler pressure). LOTS of break-in (at least a hour).

My runs are consistent and flawless with a perfect 2/4 break. If you don't want your engine, I'll also consider bidding on it!

phil c · « **Reply #8 on:** April 03, 2007, 08:07:08 PM »

Ty, your description of the problem sounds like the typical vibration induced fuel foaming for a profile ship.

bruce malm · « **Reply #9 on:** April 03, 2007, 08:45:24 PM »

Steve Fitton,
I wasn't sure on your reply if you were speaking to me or TY. What size venturi are you running.
One of the best reasons to be a member of the stunt comunity is all the information you can get
so quickly in this computer age.

Thank You,
Bruce

Steve Fitton · « **Reply #10 on:** April 03, 2007, 11:37:59 PM »

Quote from: bruce malm on April 03, 2007, 08:45:24 PM

Steve Fitton,
I wasn't sure on your reply if you were speaking to me or TY. What size venturi are you running.
One of the best reasons to be a member of the stunt comunity is all the information you can get
so quickly in this computer age.

Thank You,
Bruce

Sorry Bruce, I was posting to Ty, but didn't make it too clear. Currently I'm running a .315 in my DS 40. No particular reason for being that big, except a friend gave it to me and that was what he was running....

Bill Little · « **Reply #11 on:** April 04, 2007, 12:11:09 AM »

Mine have ~300-305 venturis and 3-4 shims per Tom on the head shims, he didn't say anhything about opening the venturi. But if you use the one that comes with it, it has less choke area than a stock Fox 35. That is the main reason there is no "40" power inthe stock ones. Plus the dude building them over in the Ukraine built them for FAI fuel, so you need shims if you use nitro!

The prop Tom was using on his Nobler was a 10.5-5.5. He gave it to me......

Bill <><

Bootlegger · « **Reply #12 on:** April 04, 2007, 10:23:03 AM »

They all look alike in the DARK.......

Bill Little · « **Reply #13 on:** April 04, 2007, 11:02:44 AM »

Quote from: Ty Marcucci on April 04, 2007, 09:13:36 AM

Thanks for the replies. I don't know why I used the fuel I did. I had a gallon of Power Masters 10% 11/11 with me. Grabbed the wrong bottle thinking of my OS .35-S in the other profile I guess. Every one says to add head gaskets, but no one ever states what thickness to use. I will add the other one that it came with. Also try a different prop. I did have an 10 x 6 on it.

I think the confusion came when I painted both planes near identically. They even look alike without the paint.

Tests tomorrow on the test stand. I will also cahnge out the needle valve ass'y to a differnt brand (ST clone).

Thanks for the help.

Hi TY,

I have no clue as to the thickness of the shims! Sorry........ I just got a handful from Tom at Huntersville, and AFAIK, they are all the same. He didn't say otherwise! LOL!! He told me to START with three, and add more if I was going to use more nitro, and that I *might* be ok with only three and 10% nitro.

The APC 10 1/2 -4 1/2 will probably be a great prop on that engine, but I just can't *look* at one of them on any of MY classic planes........

As to the stock NVA, I have never seen a problem with them.

Bill <><

Bill Little · « **Reply #14 on:** April 04, 2007, 11:10:35 AM »

To All,

I use PA engines all the time, and I really like them. The only Double Star engines I have are the 40s. They are drop in replacements for the Fox 35 and will run very good if you do the right adjustments. The DO need a bigger restrictor, and they Do need head shims if you are running ANY nitro. Are they as srtong as a PA 40UL? Nope. Not even the Aero Tiger 36, or Magnum 36. BUT, they will drop in and be plenty for a typical Classic "Fox 35" size ship. That was the whole reason for Tom Dixon having them made.

My main use of Randy's engines is a very personal thing, not a slam on anyone else or there engines! There are plenty of others out there which work very well, I just know and see Randy a whole lot, and his engines work flawlessly for me. Having said that, the DS 40s are now working flawlessly for me, too, they just wouldn't "out of the box". But the "fixes" are very, very easy.

Bill <><

bruce malm · « **Reply #15 on:** April 04, 2007, 01:45:16 PM »

Thanks Steve,
Bruce

Bill Little · « **Reply #16 on:** April 04, 2007, 04:37:34 PM »

Quote from: bruce malm on April 04, 2007, 01:45:16 PM

Thanks Steve,
Bruce

You're welcome........

Steve Fitton · « **Reply #17 on:** April 04, 2007, 08:06:14 PM »

I haven't miked the shims recently, but I believe they are nominally ten thou each. I don't have all the answers for the DS 40, because I only pull that plane out for Classic at the contests. If I actually worked on that plane, I'm sure my engine run would be even better. The 40 can be a bit picky, and seems to benefit from the venturi upsizing. My 60 works perfectly out of the box, with just the head shim adjustment to tweak the break.

I'm still missing something though, as regards the 40, because Tom constantly gets awesome runs out of his, and he swears up and down there are no *tricks* he's using to get great performance out of it. I tend to believe him, as Tom probably wouldn't expend the energy to figure out a bad-running motor these days. Some day I'll figure it out......

Bill Little · « **Reply #18 on:** April 05, 2007, 01:12:08 PM »

Quote from: Ty Marcucci on April 05, 2007, 11:34:34 AM

I measured the head gaskets. and both are .0105". I added the second one. Now we shall see.

Have you got another (three)? and what is the venturi size? Nitro%?

Bill <><

Bill Little · « **Reply #19 on:** April 06, 2007, 03:36:19 PM »

Quote from: Ty Marcucci on April 06, 2007, 11:53:42 AM

No more supplied gaskets, so I shall make some. Nitro is 10%. Venturi is bored out to .309". The needle valve Ass'y blocks a lot of the hole. I may go to a thinner set up.

According to Tom Dixon, 10% nitro will need three to four head gaskets (shims). Stock NVA *should* work fine. Give it a slight tilt off C/L as you know. I run 5% and 10% Sig Champion. (mostly 5% until it gets real hot....)

10 1/2X5 is the prop Tom gave me that he had been using. (looks like it was cut from a 12"-5 Rev Up, maybe) I also used a 10-6 (repitched to 5 or 5 1/2) Bolly 3 blade when the prop wouldn't clear on the Argus.

Larry Renger · « **Reply #20 on:** April 16, 2007, 11:40:28 AM »

Naturally, having bragged on how well my DS 40 runs, it has gone insane and won't run right. Current trick is that it will either scream, or die rich. The lovely 4/2/4 break disappeared in one flying session. It has run well for years, and still has great compression. The rod seems OK, the crankshaft is firm in its bushing, no binding. The spraybar hole is in the correct position. I tried a new plug.

Clues anyone?

Dick Fowler · « **Reply #21 on:** April 16, 2007, 01:55:42 PM »

Quote from: Larry Renger on April 16, 2007, 11:40:28 AM

Naturally, having bragged on how well my DS 40 runs, it has gone insane and won't run right. Current trick is that it will either scream, or die rich. The lovely 4/2/4 break disappeared in one flying session. It has run well for years, and still has great compression. The rod seems OK, the crankshaft is firm in its bushing, no binding. The spraybar hole is in the correct position. I tried a new plug.

Clues anyone?

Air leaks? Gasket problems?

Larry Renger · « **Reply #22 on:** April 16, 2007, 04:18:16 PM »

It will be next weekend before I can see if this is the problem, but I realized that I had switched fuels. Same nominal formula, but went from Powermaster 15/18 +2% added Castor, to Excalibur 15/10/10. The symptoms I am seeing are what I would expect from a drastic increase in Nitro content. The "good stuff" is killing me? I'll mix up some of my regular stuff, test that, then dilute some of the Excalibur down to 10%, and see how that runs.

Larry Renger · « **Reply #23 on:** April 22, 2007, 03:46:40 PM »

Sho 'enuff, when I switched back to my regular Powermaster mix the problem went away. I guess I'll need to get some extra head gaskets to run the Excalibur fuel. Sc***ed by honesty in commerce - what a concept!

EddyR · « **Reply #24 on:** April 22, 2007, 07:10:15 PM »

Ty The 40 and the early 50 have the same problem. I have found that the Rustler 40 also has to be set up like the DS motors.The 18% half and half oil works the best. Also a large intake as long as it will draw fuel. The one difference between the DS and the Rustler is the Rustler puts out lots of power and will run fast with low pitch props or slow with high pitch props.I have run mine at 10,000 in a four cycle.
Ed

Author Topic: Double Star .40 (Read 4426 times)

Walter Hicks

Walter Hicks