Engine Seizes
 

This is the second time my new .40 Tower Hobbies ABC engine sized. I have been able to free it up both times but I have yet to fly my plane because of this. I am using Omega 15% W/Castor pink fuel. The first time I thought it was because I was running the engine too lean but this time I'm sure the fuel/air was set right. Now I suspect it is happening because of an improper spinner size. Could it be happening because the spinner is too big for the engine crankshaft prop. backing plate and it is going out of balance? I know....I'm probably way off base here but I can't understand why this is happening. Any advice would be greatley appreciated.

RE: Engine Seizes
 

Does it stick with the piston at the top of the compression stroke?

RE: Engine Seizes
 

I can't tell. It seems to happen gradually. I was using an electric prop. spinner starter and it just seems to get harder to spin then freezes up.

RE: Engine Seizes
 

G'day

I think you need to tell us a bit more about the setup. Is the engine inverted? In a plane? In a test stand? Type of spinner? Prop?

I think you are saying that your starter is having difficulty turning the engine over? If this is the case, the engine may simply be flooded with fuel. If you get lots of fuel in the crank case, as you turn it over, eventually too much will cause a hydraulic lock and the engine won't turn over. You could damage it doing this.

Is the fuel tank mounted too high? The centre line of the fuel tank should line up with the carby centre line. If the tank is higher than this, it can flood the engine easily and cause the hydraulic lock I mentioned.

A true seize occurs when the piston and liner become so hot that they start to melt together or the piston expands so much that it grabs the insides of the liner so much that it can no longer move. All ABC engine "nip" a small amount at the top of their stroke. This is normal and so long as there is oil present it is not a problem. Once the engine becomes hot, this is no longer a problem as the liner expands away from the piston.

Another possible problem with spinners - the prop blades must not touch the spinner at all. It is often necessary to reshape the holes in the spinner to get the blades clear of the spinner. If they are touching, they may distort the spinner and can cause binding or worse, they may eventually weaken the prop blade and one may fly off. If you do reshape a spinner, balance can be disturbed and the spinner should be balanced but that is another subject altogether.

Does any of this help?

RE: Engine Seizes
 

Here are a couple of pic.'s of the sprinner.

RE: Engine Seizes
 

Is the starter slipping on the spinner or does the starter just not turn the engine over

RE: Engine Seizes
 

Another thing to watch with engines that have a taper on the prop-driver is that the driver itself isn't split.

I've seen this happen and when it does, the simple act of tightening the prop-nut forces the back of the prop-driver to rub against the front of the crankcase.

RE: Engine Seizes
 

G'day Let's start with the simple things first.

Can you turn the engine over by hand. Does it feel smooth?

If it does not, pull the propellor off and see if the prop driver (the metal bit behind the propellor) is cracked. This is what XJET is talking about. These things sit on a tapered collet and sometimes they split and then when you tighten the prop, it forces the damaged prop driver back against the crank case and the engine won't turn over.

RE: Engine Seizes
 

The starter will start the motor then it stalls. After a few more starts and stalls the started begings to spin over the spinner as the engine binds until it will not turn the engine anymore.

RE: Engine Seizes
 

The prop. driver looks OK, that is it'a not split or cracked. I'm going to order another spinner. If I just ask for one for a .40 glow engine I should get the right size, shouldn't I?

RE: Engine Seizes
 

OK Try this. But before we start, are you sure your battery is fully charged?

1. Take the spinner off completely. Refit the prop without the spinner.

2. Turn the rubber thing in the electric starter around so the hole in the back is facing out. This way you can use the starter on the engine without the spinner.

3. Close the needle valve completely (go easy and don't jam it in tight).

4. Open it about 3 full turns (this is a gestimate as I don't know that particular engine).

5. Try to start again.

If this works, then the spinner may have been the problem or you may have had the needle screwed out miles too far.

If it does not work we continue the investigation.

You can also buy "spinner nuts" which are made of aluminium (or chromed brass if you need some extra weight) and screw onto the engine in place of the spinner and the normal nut. Very neat and work well.

Secondly, plastic backed spinners are best avoided. The ones with fibre reinforced black plastic are ok. The coloured plastic ones tend to compress when tightened and do come loose over time. They need to be checked regularly for tightness. Metal backed are better and all metal are the best but you do need to buy a special nut to fit on the engine for them.

RE: Engine Seizes
 

I really doubt that the spinner is causing the engine to stall. I would start over with the break in procedure in the manual. The ABC engines have to be properly broken in and It seems to me that I heard that running way to rich complicated things as it wouldn't let the engine get up to temp quick enough and would cause siezing. Read the manual closely and give it another chance. The starter slipping on the spinner could be that the engine is siezing up from the short run, IE the piston is warming up, but the sleive isn't yet and things get overly tight.

A question, if the engine is cold, IE hasn't rund for at least 15 minutes, does it spin over OK? If it does, that would be an indication that you may be running to rich and the liner isn't getting hot quick enough.


Don

RE: Engine Seizes
 

That sounds like a great idea. I'll try it. Thanks.

RE: Engine Seizes
 

The Tower .40 was basically an OS FP .40. First make sure you are using a 9x6 or 10x6 prop. It's possible that the spinner is rubbing against the plane's cowl. Make sure there is about 1/16" clearance between the spinner and the model. It is also possible that the spinner and prop are slipping against the drive washer. This can cause the spinner's backplate to get hot enough to melt.

I'd just remove the spinner until you get the engine running. Make sure the prop nut is tight.

Disconnect the fuel tube from the carb and remove the glow plug. Use your starter to spin the prop. If it is flooded fuel will spray out of the head (so lean back when you do this to protect your eyes).

Then, do as mike109 said: turn the needle valve in all the way and open it three full turns. Reconnect the fuel tube and install the glow plug. Open the throttle all the way and hold your finger over the carb's opening. Flip the prop until you see fuel travel up the tubing and into the carb. Remove your finger and flip a few more times.

Now, attach your battery to the glow plug and use the starter. It should run assuming the glow plug is good and your glow battery is charged.

David

RE: Engine Seizes
 

Great advise! I'll do as you suggest as well.

RE: Engine Seizes
 

As an aside - you know me - The Tower .40 ABC was better than the OS .40FP, when you got one made within spec. Quite a bit stronger and a nice little revver. I agree with staying toward the low side in prop diameter and pitch. A 9x6 to a 10x5 to an 11x4 are good prop sizes for this engine. You will not be able to over rev it with these prop sizes, even though it might make a pretty good howl while running the 9x6. There is nothing to hurt. This is a plain bearing engine with an ABC piston/liner. The latter is superior to the OS .40FP's later nickel plated liner. I'm also convinced that the timing of the Tower engine is a bit hotter than that of the OS .40FP.

I like the Tower .40 ABC engines so much that I have began to seek them out and collect them. No, they are not worth much on the market, but that is another reason that I look for them. The bargain factor.


Ed Cregger

RE: Engine Seizes
 

Another tip, if you are not doing it. Back the prop up so that the start can get ahead start at turning over the engine. If it is a new engine and you are in a cold climate (I consider NJ a cold climate), things are pretty tight in there. Even the best of starters have a hard time starting to spin if the engine is up against its compression.

Some folks go so far as to heat up the engine (use a gas torch to get it warm not hot) on the first couple of runs to expand things and loosen it up a bit. After she has run a bit, things will loosen up, wear in, break in so to speak.

Do all those other things recommended, especially the removal of the glow plug and turning the engine over quickly to make sure excess fuel is expelled. You don't want hydraulic lock and a broken connecting rod or worse a bent one.

Cheers,

Chip

RE: Engine Seizes
 

You guys are great! I really appreciate all your knowledgeable advise and help. Thank you!

RE: Engine Seizes
 

If this is a brand new engine, running it too rich will cause it to "seize" quickly. The piston expands before the cylinder does. You must get the engine up to operating temp as quickly as possible by leaning it out. Continued attempts to run it rich will ruin the connecting rod.
Screw the high speed needle all the way in then back it out 3 turns.
Start the engine and run it up to wide open throttle. Turn the high speed needle in until the RPM's peak then back it out 3 clicks. Let it run!

I have to admit that I have never messed with a TH.40, but I do know the TH .46 and the GMS .47 quite well.

RE: Engine Seizes
 

The Tower 46 is a Thunder Tiger GP 40 and is a copy of the OS 40 FP

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If it is tight at TDC and it is cold out, i'd preheat the engine with a heatgun first, it will make starting much easier in the cold, but even when it's warm out i like to preheat it a bit to make starting easier on a brand new engine.

RE: Engine Seizes
 

First things first. Before you get the engine running take the price tag off the prop and balance it. When the engine stops turning over pick the airplane up turn it upside down and point the muffler opening down. If a bunch of fuel runs out it is completely flooded.

RE: Engine Seizes
 

G'day

Are you getting anywhere? By the way - when an engine is running, the only safe place to be is behind the prop. Never tune the engine by leaning over the prop from the front. Not unless you like getting stitches that is. And keep any observers behind the prop too. And make absolutely sure the plane cannot move when the engine is running. If it suddenly moves, the instinctive reaction is to reach for it to stop it and more than one person has been hurt reaching through a spinning prop.

A couple more questions if I may -

1. Is that a sticker on the prop? If it is, get it off as it will unbalance the prop. This can wreck the plane and engine from vibration.

2. Have you balanced the prop? You need a small tool to do this. To make the prop balanced, use fine wet and dry sand paper to sand the front of the prop on the heavy blade. You should also use the paper to remove the flashing and molding excess around the edges of the prop. This will also save your fingers if you run them along the edge of the prop and make the prop work better.

3. Have you flown an RC model before? If not, you need to find someone to teach you or you will be spending a lot of money on crashed planes. Using two similar radios and a "buddy cord" is the way to go.

4. Is there an RC club near you? If so, go there and ask for help. They will be more than pleased to help you. If not, then a small single engine electric foam plane like an Electrofun is a good place to start. Your glow powered trainer is not really suitable for self teaching. It is simply not stable enough to give you time to learn while you are making mistakes. Some people do manage to learn all by them selves, but they usually go through lots of models and their models end up made of more epoxy than balsa. Balsa flies quite well, epoxy does not.

And finally - hang in there. It is worth it in the end.

Michael from Oz

RE: Engine Seizes
 

Yea, I thought I had broken it in but maybe I didn't run it long enought. I got a new aluminum spinner with an adapter kit last night. It was about an hours ride to the hobby store. Brought the engine with me for a proper fit this time. Cost close to $50.00 ....... Yeiks! I'm sure now that the plastic spinner did not fit right. When I get it all set up again and running, I post a update.

Thanks again to everyone.

RE: Engine Seizes
 

What kind of heat gun works at the field without AC mains? Seriously. I'm out of the loop.


Ed Cregger