SRQFlyer

My Feedback: (17)

I have an older, used TT 07 that I am going to use on a Ace simple Corsair. I notice the engine leaks at the roll pin in the back of the case. What is that for - should I plug it (and how), does it matter? Also, the engine doesn't seem to like an APC 7x3. I think I test ran it several years ago on a 6x3 - would that be a better prop?

Thanks in advance,
Jim

controlliner

Clean the area well and press in some JB weld from the outside. This pin is to locate the cylinder liner in the crank case. It allows the ports in the liner to maintain the allignment with the ports, machined in the case. A 6X3 or 6X4 will allow the engine to run in the sweet spot in the power curve.

SRQFlyer

My Feedback: (17)

Thank you! I thought I had used a smaller prop for testing earlier. It sure doesn't like the 7x3.
Thanks again,
Jim

Mr Cox

The hollow pin is 1mm in diameter, you can easily replace it with a bit of music wire instead. MkII has a solid pin there from the factory, plus it has better matched ports in the case etc.

The engines are prone to overheating, so run plenty of castor (20-25% oil, all castor) in the fuel and no larger than a 6x3 prop.

I have made plenty of mods to one of mine before I got it to run reliably. One mod includes a baffle in the exhaust for better fuel delivery. More power can also be had by making a head for turbo plugs (and matching the transfer channels in the case to the ports in the liner etc.);

http://www.youtube.com/watch?v=F5sXWplWBrY

SRQFlyer

My Feedback: (17)

Thank you Mr. Cox (Mr. TT?)!
I remember at the WRAM show in the mid-90s they (ACE or maybe TT) showed the Corsair with this engine, so I'm hoping it will do a decent job. I do have a good-running G-mark .061 and also a Norvel .061 that runs well. I was just trying to make a home for this engine.
Thanks again,
Jim

MJD

My Feedback: (1)

That's a pretty decent idle for a small engine.

aspeed

They are a fairly good motor. Docile, anyway. 2 of my three go good. One was a dud. I got them all used and that is the gamble. They were $80 plus 13% tax when I looked at the hobby shop. Usually I can get them to go well, but not the one. Likely just worn out. All of mine have very sloppy crank to case joints. The two good ones rev up nice just like the Norvel .074 when I put on the Turbo head that I made as Mr. Cox directed. I just copied the stock one pretty much.

ffkiwi

The APC 7x3 is quite a heavy load with a lot of blade area (I used to run this prop on a Cox Conquest .15 in F1C)-the Master airscrew 7x3 is a nice prop-lighter, and with much narrower blades. Try this on the TT07 and you'll find it much happier. Two other props to try are the Master 6.5x3.5 and the very thin bladed 6.5x3. Remember that revs don't fly aeroplanes-THRUST does-and thrust is determined from a fairly complex dynamic interaction between diameter, pitch, blade area and rpm. A particular prop will suit your plane better than others-but only test flying will give you the answer as to which-you might find the aforementioned 6x3 or 6x4 prop works better than the larger sizes I mention-alternatively you might find the opposite. Somewhere in that 6-7" diameter and 3-4" pitch range will be a prop that suits the engine and flies the model well-but you might need half a dozen different ones before you find the best-and even in the 6x3 and 6x4 sizes you have a choice of at least 3 or 4 manufacturers-in the US-all with different blade shape, thickness, weight, airfoil and pitch distribution. Unfortunately, manufacturers have never come up with a common standard for prop pitch-some use 'average pitch, some use max pitch, some use pitch at 70% blade radius-this is why props vary so much even in the same nominal size-and why it is impossible to be specific in recommending a particular size and brand of prop as 'best'

ChrisM
'ffkiwi'

SRQFlyer

My Feedback: (17)

Chris,
Thanks for all the good info! As a follow-up, I test ran the engine again this past Tuesday with a MA 6x3 that either of my Norvel 061s will spin quite happily. Not the TT, though. It just never got up to that happy place. I'll tear it down to see if something is wrong. I think, in the meantime, I'll put one of the Norvel 061s on the Corsair.
Thanks again,
Jim (57 years in the hobby and still learning!)

aspeed

All of mine can rock the piston up and down at say bottom dead centre because there is so much play in the crank to case so it loses the seal. I tried matching the ports and the turbo head, and the head helped all of them but the one dud. I even tried soldering the case bushing to get a better seal, and the dud motor didn't respond. The other one seemed to idle nicer with that. I think I had a 6 1/2 - 3 1/2", but a 6-4 would likely be ok too. I think it has to rev a bit. I have a few 5-5" props to try when the snow goes away if there is time.