loopdeeloop

My Feedback: (4)

Yup -- got about 4 inches of fluffy stuff. The snow will be easily blown off the runway for airplanes with wheels. Those with skis will not have an issue. I have an electric powered 74 inch glider that I can toss into the air so no issue for me.

ocrcdude

My Feedback: (179)

Well guys didn't get any snow, but it got down to the low 40's last night. Winter has arrived in SoCal. Now at this time it's of the evening it's 59. Hey, that's jacket weather for us. But glad we don't have the real cold you fellows have, wouldn't know how to act. Or dress either, so stay warm.

1QwkSport2.5r

Was only about 9F today. About the only thing that will start in the cold is my ice auger. LoL.

loopdeeloop

My Feedback: (4)

Pack up an airplane (skis or not), electric, nitro, or gas and come on down to the Owatonna RC Modelers field on January 1 about 10:00 am. We will be there with eats, heat, drink and enough equipment to get even the most stubborn engine started. AMA card required.

1QwkSport2.5r

I'll have my 21mo. old son as my wife is working that day, and don't have an AMA membership yet anyway... Otherwise I'd at least come watch for a bit.

GREG DOE

Re-read my post, and you will see that I suggested using a lapping tool on the PISTON, and specifically suggested not lapping the piston to the liner, even though the result of breaking an engine in is more like lapping to the liner. The idea is to retain the taper in the liner, and keep the piston straight, so that the compression seal is at the top of the piston only. This reduces the drag, or friction that results from the seal between the piston, and the sleeve. Lapping tools are a special order tool. I have two which will work for most .40 displacement engines. Occasionally the nickle or chrome will peel on ABC or ABN liners, but that generally results from honing the too much. or a bad plating job to begin with. I've probably had a 100 ABC, or ABN engines, and have never seen one peel, but it does happen.
On another note, some of the silicone aluminum used in ABC and ABN engines (especially Thunder Tiger) has not been heat stabilized, so it is not uncommon for these pistons to grow, or swell when the engines experience over heating, or over cooling. Finally a clarification on a post about how to set the low speed needle on the GP-42. If memory serves me correct low speed on that carburetor is accomplished with an air bleed screw.

flycatch

My Feedback: (26)

I second that.

aspeed

Greg. I just wonder what your lap looks like. I have heard of a few methods, mostly home made. They need to be adjustable, right? http://modelenginenews.org/techniques/cylhone.html This shows a couple ways. I still just lap them with the piston, but was thinking of trying plating at some point in my life, and then it would need to be lapped.

GREG DOE

The "lap" is a simple straight sleeve, not unlike an engine sleeve (liner). There is no flanges on either end, but it has a spiral grove cut in it. This slot allows it to be compressed ever so slightly. There is a holder tool, with a handle on it that the lap goes in to. This holder is very robust, and also has a slot on it, with a compression screw that spans the slot. Tightening the screw squeezes the holder, and in turn squeezes the lap. The holder resembles a pipe threading die holder. Everything is made of steel. In practice the piston is rotated in the lap with compound on it. Turning the compression screw squeezes the lap smaller,and makes the piston smaller. Some sort of holder has to be used on the piston. I usually replace the wrist pin with wood dowel, and a worn out connecting rod is used. Keep in mind that the silicone aluminum used in the pistons is very porous. That helps to trap lubrication oil, but those pores can also trap lapping compound, so everything needs to be cleaned thoroughly. Here is where an ultrasonic cleaner is almost mandatory.
I've not done any plating, but I know what is involved, and I have seen a set up. Plating is done with "hard" chrome, and not "bright" chrome. You don't just throw the parts in a tank, and turn on the electricity.There has to be an electrode that passes through the center of the sleeve. The chrome then has to be honed, like in the article you referenced. Even with a diamond hone, it's slow work. The honing process keeps the sides of the cylinder straight, and round, but does not alter the taper. The chemicals involved in chrome plating are very corrosive, and industrial plating businesses in the USA are heavily regulated, to protect against pollution. Being able to plate liners is a neat capability for gear heads, but probably not worth the trouble. Speaking of favorite "rides". My 283 powered "57 Chevy has given us 17 years of nostalgic fun. It's all good, just some is better!

f16man

Well back to the original subject,,,, I see there is not much support for thunder tiger engines or parts online anyway, now that I think back a friend had a rc boat powered with a thunder tiger engine, we got it to run as good as it could but was a joke compared to the os and rossi powered versions of the same hull so I say round file it and get ya a real engine..............

GREG DOE

f16man, While there has been a lot said about problems with the GP-42, that does not mean it is bad engine, or that all Thunder Tiger's are sub-par. Take for example the TT Pro 40, and 46. They have evolved as the best sport 40's for racing. The engine is used almost exclusively in AMA 424 Quickie 500 racing here in the US, and in other countries. It's not the most powerful sport 40 available, but it's the best bang for the buck. Not everyone can just "round file" their engine, and then replace it with something at twice the price. When I finally got my GP-42's running their best, I was able to race it, in Club 40 against Pro-40's and not get lapped. I thought that was respectable. Obviously I got some Pro 40's, and gave my GP-42's away. I think if you asked the twin 14 year old's that I gave them to, they would tell you that they are REAL engines. I gave around $52.00 to $54.00 for the GP-42's, about 7 years ago. It was a "speck" engine for a local rules racing event. I would not normally buy a cheap, plain bearing engine like the GP series, so for most of my needs, Thunder Tiger engines are not at the top of my list. (Not all TT's are plain bearing) Not everyone in this hobby can afford the best, so when someone gets a lower quality product I'm happy to help them if I can.
It's true that we have gotten off subject, but I think a lot of useful information has been exchanged, as well as several opinions, and the knowledge that lots of folks have experienced problems with GP-42 being VERY tight.

f16man

Exactly and being very tight is a sign of poor machining......... But you are right any engine can be made to run as good as possible, I don't think that con rod is going to enjoy that tight cylinder for very long,, one thing I have done to some of the rossi 81 df engines was pull the head off clean the cylinder and piston with alky and rub some tooth paste on the walls of the cylinder, stick the head back on with glow plug out and buzz the engine over with the starter for maybe 20 to 30 seconds, take it back apart clean every thing up and re assemble, I don't think it really took more than a .0001 but it really polished the tight area and did loosen things up a bit, we also had to start with glow plug loose for say the first 10 tanks of fuel at 16 oz per tank after that we could lean them out and get some rpms out of them, all engines were broke in on the plane pushing a Byron fan with not much forced air flow,,,,,, did loose a few con rods back then until we started using full roller bearing rods I custom made on my milling machine.

1QwkSport2.5r

If you think a tight P/L fit is a bad thing, you got it ALL wrong. Like WAY wrong. But whatever. Believe what you want.

AllModesR/C

Tower Hobbies used to sell and support TT until very recently. I was able to get exhaust manifold gaskets from them. I bought this plane complete and this is the engine that come in it.

aspeed

I think the OP is only having problems with the very cold weather. California normally would not have this problem. The brass sleeve is just shrinking a bit more than the aluminum, making it too tight to run in 40 degree weather. It is likely fine in warmer weather. I don't think it is a TTiger problem, other than being a bit on the tight side. I will admit that TT is not my favorite brand, but they are fine for a trainer, and give good service. Running the motor will hardly make it much looser if the brass is a faster expanding metal than usual. As soon as it runs off the prime, it is hot and loose, so there is very little friction. I think just warming the cylinder will solve the temporary cold start problem as has been mentioned. My little Norvel has the same problem with the sticking. I will just wait until spring.

GREG DOE

aspeed, Helical Lap Co. helicallap.com Look at "External Laps & Lap Holders". I got my laps before the internet. Probably 30 years ago,
so I had to do some research to find them. This will at least give you a picture to look at. Good luck if try give it a try. Greg

f16man

No I don't think I have it wrong I am a 61 year old precision machinist and have to deal with fit and finish all day at work, if the piston is truly that tight it is very possible that one or more engines slipped thru qc at $60.00 bucks they wont spend too much time with the finish ,,,savy????

1QwkSport2.5r

I'm not savvy to your thinking. Get your hands on one of a Dub Jett's fine engines. He sets his engines up pretty tight, and for good reason. I trust his premise and reasoning on fit and finish over all else. Tight engines seal better and therefore run better, run stronger, and last longer. Granted, his engines all have chrome plated bores as it is more durable than nickel. A really tight nickel plated liner should hold up well provided it gets plenty of lubrication during its life. Tight engines take longer to break-in, so those that want instant gratification will find themselves more frustrated as their engine will take longer to reach full power potential.

Just my opinion. No gospel spoken from me.

aspeed

Interesting website. I was really wondering more about an internal lap, and there was a sketch of those too. They use cast iron, I guess it holds the compound best. My lathe can almost hold .0002" on a good day, so an external lap would not be needed.

f16man

I am not here to argue over who's the best or worst all I am saying is I have run across some engines set up too tight as in sticking a piston even at rich setting and 20% oil , it is good to be a tight fit but too tight is too tight, in this case it is likely a cold engine that has not been run in all the way.....O ya I have run Jett engines and are tight but are the right amount of tight other wise he would have troubles ,ask him how many pistons he stuck before he found the perfect fit!!! and comparing a custom hand built engine at $400.00 to a thunder tiger is not even worth the effort.

1QwkSport2.5r

All I'm saying is a tight engine isn't a bad thing. A thunder tiger is nowhere near as tight as a Jett, so if you get a tight thunder tiger, I'd consider myself lucky. Thats just me though. We are free to believe what we want.

f16man

Yes sir we are free dispite what the government thinks

1QwkSport2.5r

+1 to that.

braddock VC

I've had several TT42 GP engines and yes they are tight, the answer is to use only synthetic oil with no castor at all. Over here in the UK they'll start no problem at around freezing, some guys have a special priming bottle with 20% nitro in plus a few per cent ordinary lead free gas, this gets them going ( not just for the TT though).
My starter has a 2800 mAh lipo 4s gaffer taped to it, it's a 25 C rated battery and that whips over my abc 61 and 91 no bother at all, the TT 42 don't stand a chance, mind the starter coughs a bit at my saito 125 when it's cold.....
I really reckon the TT 42, because it's plain bearing it can be neglected without any bad effects and is MUCH more powerful than the OS 46 LA. I run mine on 10% nitro with pure synthetic oil and it really doesn't pose any problems in the winter. Trick is to get it up to temperature pronto once it's started and don't richen it up too much at the peak.
Just my 2c.

1QwkSport2.5r

One thing to keep in mind; here in the US we don't have the same synthetic oils folks have in Europe and the UK. Synthetic oils like Motul and Aerosave are significantly better than the PAG type synthetics often found in commercially made fuels in the US. Those PAG synthetics do not perform as well as the Ester type oils found elsewhere in the world. With that said, using solely PAG oil containing fuel in a bushing engine is certain death to the crankshaft and bushing IMO. Personally I'd never be convinced otherwise unless we could get the European synthetics at a more reasonable cost. Last time I checked, a U.S. importer I found online sells Motul Micro for $80 USD per gallon where Klotz is $40/gal (PAG).