I think it sounds good too. I want to run the 10x5 once and see what kind of rpms I get. I have a strong feeling the 9x7 (though it spins fast) isn't going to be enough thrust to get this pig moving.. This little .46 needs to move a 5lb Outrigger around. I think the numbers I was getting with the 10x6 (14,600) wasnt all it could do. I would think it should be in the 15k area but time will tell. The 10x6 and 9x7 have close to the same prop load, so I would think the 10x6 though slower will move the craft faster. I think the 10x5 might be the meal ticket if I cant get any better RPMS from the 10x6. Bob in the Jett forum said something about having the engine over 15k to really be working the pipe so thats kind of what I'm shooting for.

The boat this engine is going onto can't run on land, but my K&B .65 flatbottom boat does about 33mph on the water, and maybe 40 on grass.. I haven't tried it on snow yet... (I have a 13x6 on it now and I have a 13x7 waiting for it... have to add ballast to the front before I put the 13x7 on it. At 33mph its airborne and eventually upside down.)

Hi!
Sounds rather good!
But... I would like to see you needle the engine...from a little rich to full rpm! Can you do that!?

The TT .46 Pro is a strong motor, your numbers are only a bit better than most.  But it also depends on the muffler you are using.

I certainly can do that. Sometime later this week I'll try to get the stand back out and bring my tripod along and let 'er have it some more. I have 3 other props I want to try out on it so I'll probably go to the park where nobody will be bothered with me and my crazy noise for an hour or two.

In the mean time I'm going to re-tool my test stand a little. The throttle lever needs to be modified, and I'm going to make an insulated stand for my tach to get mounted to. I have verified the tachometer's calibration as I get 3600 on the screen when pointing it at an incandescent light. (At least thats what I was told on my airboat forum..) I plan to make 3 vids of the 3 props, and I'll "needle" the engine with all three. I'm not a master tuner, but I know when it sounds the nicest means its at max power.

Don't know what the temps are in Minn. but it's warming up here in central N.Y.
You might not need as much of that alum. tape wrapped around the cyl....if any?

I took it off mine when the ambient temps got into the high 30's

Well, thats the reason I have a temp gauge strapped to my stand. To make sure the engine stayed warm enough anytime it was running. It had a harder time staying up to temp with the smaller prop on it - about the only time it was over 220° was when it was running WOT or close to it. The temp would drop like a lead weight to 190° once off WOT. The days I've been testing the engine have been in the mid 30s, and even though it was warmer this little bugger moves some serious (cold) air.

The next time I run it I'll have it running for a longer time so I'll probably pull it off if it holds temp above 220° okay. Thats my main concern. Even though I only have $100 into the engine and pipe together, I want to prolong its life as much as possible.

Got Snow? Thought you had snow till about mid March. Though there may be periods of a few days to a week or so without snow on the ground. At least thats how I recall it on visits.

I got about 16" in the yard and the snow piles on the edge of the driveway (as seen in my videos) are about 4 1/2 feet high. Not much melted this year - it's been really cold here.

tomorrow is going to be in the 40s so I'll go flog the test mule tomorrow.

Alright.. I didnt mess around too long since the wind kicked up some.. Air temp outside 41°F, wind at 15mph. Not ideal, but what the heck.. Starting off I went noticeably rich, then leaned past peak and richened back to close to full RPM. In one of the videos, I went way rich twice by accident. My tach jumps around a bit - I'm gonna find a more accurate one this summer sometime.
9x7 APC, 5% nitro / 20% oil (75% castor/25% synthetic), MC59 plug
http://s153.photobucket.com/albums/s...t=MVI_0010.mp4
10x5 APC, same fuel/plug
http://s153.photobucket.com/albums/s...t=MVI_0011.mp4
10x6 APC again, same fuel/plug
http://s153.photobucket.com/albums/s...t=MVI_0014.mp4
Transition is pretty good - Idle mix is a tad rich still - didnt touch it in any of these 3 runs because I didnt feel it necessary.

Hi!
Sounds got to me!

Thank you, Jaka. I thought so too. I'm really happy with it at this point. The engine is almost to 1/2 gallon so it should get better.

When I first got the engine, I thought the pinch was pretty mild at TDC considering the engine hadn't ever ran when I got it. Even today it feels the same as it did when I got it - very slight. Compression is very good though. Look forward to running it on the water.

Will a Graupner cam prop or RAM prop turn that much faster than a APC? Are they worth the shipping costs to the U.S.?

Hi!
The Graupner Cam prop (Black variant) is rather expensive. The RAM 10x6 is equall to the Graupner 10x6 so I would try that one instead.
RAM are British made props.
But...The APC line of props are prefered in most cases when it come to delivering good performance. So you have to check your self.
The only props you should avoid are the white tipped Master A props. They are loud and give poor performance. The MA "scimitar" line of props are rather good though.

How do you think 5% nitro performs compared to 15% nitro that seems to be the norm in the US??

I'll have to look and see if there is a U.S. Distributor for RAM props. If they are better than APC by a decent enough margin, I would buy one to try. I'm done with MA props - I wont use them anymore.

In regard to the Thunder Tiger .46 testing, it doesn't seem to make a big difference on RPM between the 15% and the 5%. The optimum needle setting is narrower with the 5% mix, but aside from that it seems to run fine. The engine restarts very well.

My K&B .65 sportster engine however doesn't take to 15% nitro well. It tends to run quite a bit hotter than it does on 5% nitro, so I'll probably run 5% nitro in both engines, and 20% all castor oil.

Hi!
Don't missunderstand me...APC make very good props but under certain conditions, like in Q-500 pylonracing over here in Sweden where we use 80/20 fuel and 10x6 props, RAM and Graupner Cam-props beat APC!
But!...In Sport 40 pylon (That we raced 15 years ago) where we used 9x7, 9x6,5 and 9x6 props and (428) Q-500 pylon where we run Nelson and Jett engines ...APC was and is king!

So it kinda sounds like APC is tops in the 9" prop range and Graupner for the 10" props.. I'll look into it more later on. Thanks for the information, Jaka.

On a side note - The 9x7 and 10x5 APC props I have were really difficult to balance for some reason. I'm guessing the hole in the hub is off-center a tad bit. I got them as close as one could get.. The bigger APC props I have (13x6 and 13x7) were almost dead-on balanced.

Are the RPM limits higher on the Graupners/RAM props vs. APC? I know the APC's are supposed to handle more RPM than any MA prop made (AFAIK), but what is the limit? I've been a little leary of spinning this 9x7 at 16,500rpm because of the cold. I'd hate it to flex and break throwing chunks in whatever direction they decide to go.. (Haven't been bit by a prop yet - I'm keeping my fingers crossed)

The regular APC props can take 190krpm/diameter(inch), i.e. 19000 rpm for a 10" prop: [link=http://www.apcprop.com/v/html/rpm_limits.html]APC safety limits[/link]

The drilled hole is a hit and miss on the APC but the casting from the back should be better.

I use a Top Flite balancer, and I've found that the two cones that center the prop on the balance shaft wont hold the prop tight. (The points on the cones touch before they hold the prop tight) So I've been turning one of the cones backwards (flat edge goes on the backside of the prop against the prop shaft hole) and pushing them tight. Once it balances, I flip it over and check it the other way. If it balances both ways, I call it good enough.

Is there an adapter I can get to balance these props better?

I have to revive this thread for a little more help. I have installed this engine on my airboat inverted as I intended. The first time I tried running the boat, The engine seemed to run fine. The boat just wouldn't plane out using any of the props I had. The engine started cold fine - Set the fuel mixture on the high side to 3 clicks rich of peak. I didnt have the tach handy so I do not know off hand what RPM it was running at. I set the idle mixture as close to dead-on as I could - the transition was flawless. The boat just wouldn't plane out. Later in the run, I was seeing air bubbles in the fuel line. Very small. I added a little more insulation to the fuel tanks compartment to better isolate the tank. I installed new fuel lines from clunk to the carburetor, including some fuel line clamps to ensure a positive seal on the fuel fittings.

Fast forward to today. I re-worked the engine mount moving the engine further back - 2" to be exact. Same fuel system, fuel, glow plug, and radio settings as first attempt. Engine started cold fine as usual, set the mixture in the same fashion as before. Tried planing the boat several times, all the while the engine ran just fine. Once it got down to about 1/4 tank, it started quitting. I refilled the fuel tank, restarted and same thing - engine kept just up and quitting. At first I had seen a few tiny air bubbles only at random so I moved the fuel line going to the carb away from the engine more and I didnt see any more bubbles. I ran almost 1/2 quart of fuel without seeing any bubbles. SO... with glow left on, it would stay running longer and better enough to try running the boat in the water more. Not much quitting with the glow left on. If I pulled the glow off, it would quit within 5 seconds of pulling the glow, no matter the RPM. I adjusted the idle mixture richer and dropped the idle rpm some to see if it just wasnt drawing well enough. No dice. It got to the point where even leaving the glow on just having it sit on shore while throttling the engine some it would still quit. No air bubbles seen in the fuel line any time it quit. SO the $1,000,000 question is this: If the fuel is fresh (5% nitro/20% castor), the glow plug (MC59) is fresh, The fuel mixture was set 3 clicks rich of peak/idle mixture set for flawless transition, and the fuel tank and lines was isolated from the hull as much as can be done, Is the quitting simply a matter of a lack of fuel draw, or is the fuel putting the element out? It seemed that it was flooding out in the low to part throttle settings, so I set the idle mixture as lean as I could maintaining that perfect transition. At the end of the run, It was not staying running with the glow left on - after running on high throttle trim for 3-6 seconds, it sounded as if it was loading up and shortly after would quit. I am just gonna go on a limb and guess fuel draw as the culprit. The engine is currently 1-1.5" further away from the tank than it was on the test stand where I had it running perfectly. The fuel tank is 3" back from the carb(front of tank to center of carb), and 6.5" below it. (center of carb to center of tank) This is story overload, sorry. I didnt have a camera set up to take a video so I had to explain it. What am I doing wrong? It worked fine on the stand, but not in the boat.....

The engine-related variables:
Main prop used is APC 9x7, also tried APC 10x5 and 10x6
Fuel is home-made 5% nitro / 20% castor / 75% methanol. Nothing else added.
Brand new McCoy MC59 glow plug, Brand new FOX Idle bar plug, and a K&B plug (unsure of heat range - it came out of my early '90's K&B Sportster drone engine) the MC59 proved to be the best plug of the plugs I tried.
All new Dubro medium fuel tubing with clamps
6oz Hayes fuel tank
Jettstream muffler

I'm not as hard core as many regarding tank position but 6 inches below the carb seems like too far.
Is the tank that low on the test stand?
Was it that low, in the boat, when you ran it with no issues?

The tank was an inch farther forward on the test stand than it is now. The engine was 2" farther forward when it was running better. It doesn't make sense because when the engine up and quits, a few drops of fuel drips from the carb. It was always seemed to draw fuel fine on the stand and in the boat. Turning the engine for 2 seconds gets fuel to the carb using an electric starter. It flooded a few times yesterday which I never had a problem with. I didn't plug the exhaust or carb to prime I either because I've never needed to.

I am going to move the engine back 2-3" more to see if it cures the problem.

Since the boat does not run inverted, then as long as he can get enough muffler pressure it should work. The distance is not anymore than when a model aircraft is pulling fuel from the back of a nearly empty tank when pointed straight up.

So should I just run onboard glow and a hotter plug? Maybe fuel draw isn't the problem, but I don't know why it won't stay running with glow disconnected. It ran with glow disconnected just fine on the stand and never flooded.

Sounds like either you need a new plug.  Glow plugs often give out during break in and bench running.  Or a hotter plug.   It could also be a rich mixture, but I am guessing you know to peak it out and give it about 3 clicks rich, or better 300 RPM rich using a tach.   With the long run I would expect small bubbles before the fuel gets to the engine.  Its from a small amount of fuel flashing from a drop of pressure and nucleation.   As long as they are small enough that they don't cause the engine to surge or quit, then don't worry about the bubbles.</p>

Quote:

ORIGINAL: 1QwkSport2.5r

...It ran with glow-driver disconnected just fine on the stand and never flooded.

The 'automatic' answer here is that the low-end mixture setting you are running now, is too rich...

The setting on the test stand should have been richer than you now have, with the tank 6" lower...
So, the engine should now be running leaner than it did on the stand.

Putting the glow-driver to work could keep the engine running in a rich setting, but it would conk out just the same, if it set too lean.

So, I can only conclude that you richened the low-end mixture, or that you are running a muffler that gives you a higher fuel-pressure, than you did during the break-in.


The other possibility is that your glow-plug 'went south'...

I tried 4 glow plugs 3 of them being new ones of different brands. No dice. Bought a VP-30 fuel pump today, and I'll grab some more glow plugs tomorrow. The bubbles I was getting would join into bigger bubbles causing the engine to hiccup a little bit. The fuel line going to the carburetor was touching the outside of the cylinder so I moved it away. Problem solved.

The tank setup was nearly the same on the test stand as it is now. 6" below and 2" back from the carb on the stand and 6" below and 3" back from the carb now. The engine ran better when it was 6" below and 5" back.

The Jettstream muffler's pressure fitting has a much smaller hole than most of my other engines, but it does provide plenty of pressure to the tank. I've concluded the problem is an overly rich idle mixture to promote fuel draw is drowning the glow plug. I talked to my local engine guy and he confirmed my suspicions. I bought a Perry VP-30 regulated fuel pump to overcome the issue. I didnt want to buy a pump because so many people said it should draw fuel fine and I was being a cheapass. I rescinded my cheapness and bought the pump. I'll test the pumped engine in the yard before going to the lake to verify its operation. I will vent my fuel tank to atmosphere running a tube up onto the engine stand so any splashing of fuel wont soak my fuel tank compartment.

This should fix the problem. I'll post my results after a Test run.