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Dave Brown mounts and mounting screws

Old 09-27-2002, 09:47 AM
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Default Dave Brown mounts and mounting screws

I've settled for a round DB mount on my Calypso 60, but I found the beams are tapered, so I can't use machine screws and bolts to mount the engine!?

The screws that come with the mount are more like wood screws, I'm curious if they'll work or not with an OS 61.

Not particularly happy forcing that kind of screws into a brittle nylon/glass mount!

Am I right in being careful here, or does the supplied screws do the job nicely? I can't belive they'd sell all these mounts if it'll break or loose the engine but I think the idea of wood screws in a nylon/glass mount is a shaky deal at best.

Any advice greatly appreciated!

Jon
Old 09-27-2002, 09:59 AM
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Default Dave Brown mounts and mounting screws

With the right sized drill bit the supplied screws will hold just fine in these glass filled mounts. There iss no need to use backup or lock nuts.

Vince
Old 09-27-2002, 12:13 PM
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Default Dave Brown mount

I use these mounts all of the time. I take the sheet metal screws and add them to the collection that I already have. I then drill and tape the mount for a 6-32 allen cap screw. That is a internal hex screw. Be sure and use the black hardened ones.
good luck
Lee
Old 09-27-2002, 12:19 PM
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Default Dave Brown mounts and mounting screws

Great advice, thanks guys. What's an allen head screw btw? I mean the head is not important, but are the threads any different from the supplied screws?

If I were to use the supplied screws, do I drill and tap, or do I drill a slightly undersized hole and use the srews directly?

Jon
Old 09-27-2002, 12:54 PM
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Default Dave Brown mounts and mounting screws

The first time I saw this method used was back in the early 70's. The Lanier line of ARF's recommended using sheet metal screws and supplied them in their kits. The procedure was to mount the engine and tighten down the screws. After the first flight, they said to re-tighten the screws. They never got loose and seemed to do the job just fine, and this was on .60 powered models. As long as you drill a pilot hole of the correct size, sheet metal screws should work fine.

I've used the Dave Brown mounts for years (they are my favorite mount) and have never had a problem, but I also prefer to drill and tap mine for socket head screws. I use a flat washer on the engine lug and a split-lock washer on top of that (under the head of the bolt).
Old 09-27-2002, 01:49 PM
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Default Dave Brown mounts and mounting screws

Jon,

I have found sheet metal screws to work just fine in the nylon mounts. I personally would not recommend tapping and using machine screws, any more than I would do that with wood. For a secure grip, the hole needs to be a bit smaller than the screw. I usually try to drill a hole which is about the same diameter as the shank of the screw, so the threads have to cut into the plastic ( or wood ). If you want to use machine screws, I would use your Dremel, or a file, to make a flat on the bottom of the mount arm. Then you can place a blind nut, or use a washer and a lock nut, or lock it with a second nut. The idea of trusting a tapped hole in nylon makes me uneasy, but maybe I am the one who is too cautious.

banktoturn
Old 09-27-2002, 02:40 PM
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Default Dave Brown mounts and mounting screws

I'm a recent convert to the sheet metal screws. Just did an ASP 1.08. I've used them on .40 and .60 sized with no troubles. Allan heads are hex heads.
Edwin
Old 09-27-2002, 03:28 PM
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Default Dave Brown mounts and mounting screws

I forgot to mention: definitely go with the Allen head screws, and buy allen drivers for them. Don't get the little "L" shaped allen drivers, get the kind that are just like screwdrivers with hex ends. Even better, get the ones with 'ball' ends. This makes it much easier to keep the driver engaged as you drive the screw, especially in tight quarters, which is what you usually have in the neighborhood of your engine

banktoturn
Old 09-27-2002, 04:31 PM
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Default Dave Brown mounts and mounting screws

The last Dave Brown mount I bought gave very specific info on the size drill bit to use with the supplied screws. Dzl
Old 09-27-2002, 07:03 PM
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Default Dave Brown mounts and mounting screws

Been flying for over twenty years now, never have had any problems with sheet metal scews in the composite mounts.
Old 09-27-2002, 07:33 PM
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Default Dave Brown mounts and mounting screws

Just use the recommended drill size that came with the screws. Use a little oil in each hole to aid in driving the screws. DON"T drive the screws to fast, they will heat up and break ! What a mess trying to get the broken screw out from the mount ! Don't ask !!

Ugo
Old 09-27-2002, 09:56 PM
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Default Dave Brown mounts and mounting screws

bankoturn

I've been drilling an tapping glass filled mounts for use with socket head machine screws for many years. Works fine and never had a problem. But I do use a split lock washer on top of a flat washer as I described earlier.

I think I would be reluctant to remove material from the bottom of a tapered glass filled mount to make it parallel with the top. What I used to do (before changing to tapping the holes) was to make a tapered piece to add to the bottom of the mount for tightening the nuts against, but tapping is a whole lot easier.
Old 09-27-2002, 10:58 PM
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Default Dave Brown mounts and mounting screws

Originally posted by banktoturn
Jon,

I have found sheet metal screws to work just fine in the nylon mounts. I personally would not recommend tapping and using machine screws, any more than I would do that with wood. For a secure grip, the hole needs to be a bit smaller than the screw. I usually try to drill a hole which is about the same diameter as the shank of the screw, so the threads have to cut into the plastic ( or wood ). If you want to use machine screws, I would use your Dremel, or a file, to make a flat on the bottom of the mount arm. Then you can place a blind nut, or use a washer and a lock nut, or lock it with a second nut. The idea of trusting a tapped hole in nylon makes me uneasy, but maybe I am the one who is too cautious.

banktoturn
banktoturn,

I have been using machine screw in all of my Dave Brown mounts and have yet to strip one. I run an S.T. 2300 in one and an O.S. 1.4 and and O.S. .60 in another. You must have the holes drilled stright (use a drill press) and when you tap you need to run the tap out after about going a 1/4 of the way in. Takes a little time but works just fine. If you still dont feel right about it drip some thin C/A in the holes, let it cure and retap.
I find using the supplied screws difficult to use since they are a straight slot screw. A socket screw is much easier to torque. If you still dont feel right about then use a socket head screw. Its up to you.
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Old 09-27-2002, 11:24 PM
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Default Dave Brown mounts and mounting screws

I have used socket head machine screws.
When you tap the hole do not run the tap all the
way thru, leave the bottom 1/8 or 1/4" untapped,
this will make it tight for the screw to go thru and act like
a nylon locknut. I dound out about this from a newsgroup.
Old 09-28-2002, 09:18 AM
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Default Dave Brown mounts and mounting screws

This is some great advice, thanks guys!

I'll try the supplied screws and feel pretty comfortable now

BTW, TOYMAKER, that's a sweet mount! Is it a hyde-mount? Which size? bought or self-made?

Jon
Old 09-28-2002, 11:38 AM
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Default Dave Brown mounts and mounting screws

I too have puzzled over the slot head sheet metal screws supplied for engine mounting. Nothing is more frustrating, (and dangerous) than trying to torque these screws in with such an unreliable interface as a slotted screw driver!
I have a low opinion of kit manufacturers who supply slot head screws for anything. Philips head should be the minimum standard, and allen heads should be supplied anywhere high torque will be needed to ensure safe and secure connection.

By the way, I'm pretty sure you can get allen head sheet metal screws in these smaller sizes. (Best of both worlds)

There's my 2 cents. At least I feel a little better.

Fever
Old 09-28-2002, 12:41 PM
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Default Dave Brown mount

flyingfever
I completely agree with you. I got over my frustrations with the mfg a long time ago by always converting these mount to machine screws. I can not even imagine going back to unhardened sheet metal screws. The mfg supplies #4 screws the 40 size mounts and #6 with the 60 and larger mounts.
And worst of all they are flat heads and soft material as an extra plus. I think they supply these screws to save cost and advertised the only tools necessary is a screw driver and drill.
The first of this type of mount that I can remember was called Kraft Hayes. Maybe 20 yrs ago or more. I broke two screws of in the first few mounts that I used. These were the 40 size mount with the #4 screws. No way to get the screw out. Had to throw the mount away and buy another one. After breaking the second screw I went to hardened allen cap screws and never had another problem. When these mounts are threaded they thread just a very small amount undersize. This is good now the entire threaded hole works like a nylock screw. I have never had a thread to fail or a screw to come loose. In the instruction the mfg tells you to retighten the sheet metal screws after a short period of use. This should make a light bulb go off in our brains. If the proper hole was drilled the sheet metal screws will never come loose on their own. So what is happening. The soft material of the sheet metal screw is streatching. I have never had this to happen with a hardened (black) allan cap screw. Another problem already discussed is the problem of orientating that flat blade screw driver to get the thread started at the beginning. Allan cap sheet metal screws are available from the company that sells bulk screws. The problem here is they don't make hardened ones and subject to the stretch problem and other failures.
Lee
Old 09-28-2002, 03:06 PM
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Default Dave Brown mounts and mounting screws

Originally posted by Jon Wold
This is some great advice, thanks guys!

I'll try the supplied screws and feel pretty comfortable now

BTW, TOYMAKER, that's a sweet mount! Is it a hyde-mount? Which size? bought or self-made?

Jon
Homemade yes!! I use it on all my bigger engines, it does require the use of a nose ring. Those are Dave Brown .60 size mounts split to accomadate my bigger engines.
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Old 09-30-2002, 06:55 AM
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Default Dave Brown mounts and mounting screws

Originally posted by TOYMAKER


Homemade yes!! I use it on all my bigger engines, it does require the use of a nose ring. Those are Dave Brown .60 size mounts split to accomadate my bigger engines.
I'm sorry for straying off topic here, while the sheet metal screw debate is ongoing (I'm a little more scepctical again now LOL)

I've seen a hyde-mount tutorial, and it looks pretty simple and effective, but I get lost when it comes to the nose-ring! What purpose does it serve? What is the effect of not having the nose-ring? is it fastened both to the front of the engine and the firewall?

Regards,

Jon
Old 09-30-2002, 01:05 PM
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Default nose rings and soft mounts

When you go to the larger engines and a soft mount the engine will osilate if it is not held in place at the prop shaft. The nose ring stabalizes this condition and only allows the engine to move in a rotational plane. Thus you have no problems then with thrust changes. Also, engines like the hard banging 4-strokers would probably pulverize the nose area with out a nose ring.

This mainly applies to the rotational dampning mounts like the Hyde mount. The nose ring is mounted to the fuse at the nose and usually has a silicon like tube lining in the nosering that has a tight slip fit over the front of the crankcase of your engine.

This picture is my home made nose ring but you'll get the idea.

Have fun....
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Old 10-01-2002, 07:18 AM
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Default Dave Brown mounts and mounting screws

Very good info, thanks much!

If no nosering is used on a smaller engine (46-61-size) what sort of diameter of the mount would you say was sufficient? Or do you not recommend it's use without the nose-ring, even on smaller engines?

Jon
Old 10-01-2002, 12:16 PM
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Default SMALLER ENGINES

I wouldnt even mess with trying softs mounts on anything smaller then a .60. But if you go that route then the Lord type mounts work good with the smaller engines. Go to this website for the basic idea on making a mount like this.

http://www.piedmontmodels.com/

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