engine mounting

Why is it that every used stunt engine that I see has had the mounting holes opened up? Does no one trust M3 ( or 4-40) bolts, or am I missing something?

I haven't seen that many with the enlarged or elongated mounting holes. If I want to mount a different engine on a model which has been drilled for a different size mounting pattern, I typically fill the old holes in the maple with JB Weld and drill the new ones.

Also, I've never used a larger engine than a .40 so the 4-40 bolts are just fine. Even with 1/8" holes in the maple mounts, the 4-40 bolts are a loose fit. I find a 7/64" bit makes for a much more snug mount but requires a great deal of precision.

LAST EDITED ON Aug-19-03 AT 07:39 AM (CDT)
 
I think a lot of folks have trouble drilling the holes in the bearers in the right places. I bought the little tool shown from Tower...it's in the Great Planes or Hobbico lines, I think. It works slick to put a pilot hole exactly where you want it. About $9. The only gripe I have with it is that it comes in a sturdy plastic tube with rubbery plugs...and you need to keep it in the tube, but the plugs have shrunk and fall out. Storage is an issue, but you'll look all over the shop, once you try it. Steve

Edit: Great Planes "Dead Center" TM engine mount hole locator. PN TE2638, $7.99 in an old Tower sales catalog from "the Library".

Yup, got one of dem. Paid $4.99 for it (really got to watch for those Tower specials). Using one is really a two handed operation so read on!

I like to have the engine a snug fit between the bearers. Sometimes I have beveled the inside faces (the ones which face inward to each other) so that the bolt holes go through the middle of the 3/8" maple.

You also have to be careful if there already is a slight gap between the motor and the bearers - it's very easy to get inadvertant up or downthrust built in (don't ask me how I know).

I've devised a system where I take thick paper stock (the paper which is used to hang the little hardware packages on the pegs in the stores is ideal) and cut them into strips 1/2" wide. You'll need about six or eight. Fold them in half along the long dimension. Use these to shim the motor exactly centered between the bearers. If you have three top and three bottom you know you've split the gap perfectly.

I like to use a spring clamp to hold one lug of the motor to the fuselage while adjusting to get 0-0 up/down thrust. Once you get it aligned, use the dead center tool to pilot a single bolt hole and drill it on a drill press. Use the one bolt to mount the motor to the fuselage then locate and drill each hole individually. How many of us have drilled all four holes only to find at least one doesn't line up?

Take your time and get it right the first time!

You can make it a one-handed tool very easy by replacing the spring with a slightly longer/stronger spring.

Too nice..

If you don't have one and need something sooner, go to your local hardware store and buy a long "finish" style nail (not a little one, at least 4" long, with no conventional head). You can chuck this into your drill and use the engine itself as a guide to mark the holes perfectly. It makes a tolerable dent for a pilot hole.

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"If the Lord can see His way clear to bless the Republican Party the way it's been carrying on, then the rest of us ought to get it without even asking." -Will Rogers

Yes, Larry. Like the Democrats should be proud of their last representatives. Steve

OOps. Forgot. The Noble Republicans don't seem to have a sense of humor, can't even smile at a comment made by Will Rogers from many decades ago.

Sorry to trip your trigger.

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"A clear conscience is a continual Christmas" - Benjamin Franklin

Enlarged holes? I see them all the time on Swap motors.

Reason? Pure laziness? People use the lug holes as a drill guide.

All they need to do is mark, remove engine, punch the marks to give the drill a good start, and drill. Good to use a drill press here, to get vertical holes.

I use the folowing trick:

Spread a thin film of oil over the mounts, put the engine in place, and sprinkle some talc on the holes.

Remove the engine and the exact location will be a white circle, made of talc...

In Christ,

Hi Steve. I got won o' dem too. I also lost one of the plugs, but the other is super glued in place. That tool takes three hands to use at times

LAST EDITED ON Aug-19-03 AT 04:01 PM (CDT) by ()
 
There sometimes is another reason--- two different engines mayhave slightly different spacing. You really can't make a separate set of mounting holes, so out comes the file.

Although I would never admit to having done this myself , I feel that I buy the engine for myself, not some future collector. Besides, with a large enough washer, no one else will notice.