CloudSkipper

I was wondering if the sharper and sparser threads on wood screws could possibly fracture (or micro-fracture) the metal on the engine. I made a notch in a thick wood plank for mounting my 46AX for breaking in. The wood is too thick for any bolts that I have handy. So that's why I used wood screws.

I haven't started up the engine yet. Would you ever use wood screws?

Thanks

ThumbSkull

My Feedback: (57)

Ive used 2 1/2" drywall screws in pine before. Held well on a Saito 1.80.
On the small 2-strokes I use 4-40 or 6-32 with nylock nuts through 3/4" ply.

buzzard bait

Hadn't thought about it that way, but back when maple beam mounts were standard design we used wood screws all the time. I wouldn't be concerned as long as they fit the holes easily and are long enough to get a good grip on the wood.

Jim

CloudSkipper

Thanks for reply. So I guess if wood screws caused no damage with a 1.8 four stroke, then a 0.46 two stroke should be fine.

I've got the engine installed with the wood screws and would like to just move ahead with the break in. But if it's definitely wiser, then I could delay by a couple of days until I can swing by the hardware store for longer bolts.

CloudSkipper

The screws slide through easily. They are not tight, but they are Not clearly narrower than the mounting holes either.

The screws by the way do not have the smooth part near the screw head either. They are threads all the way... hence my concern.

iron eagel

I have used them with no problems on the old woden beam type of models with no problems. Some of the plastic/composite type of mounts use screws as well...
As far as the threads extending all the way to the head yet another non issue.
If do not over tighten them and you should be fine.

CloudSkipper

Cool thanks. I've had too many delays with this plane. So I can just proceed with the break in procedure without going back and changing something.

nonstoprc

My Feedback: (90)

Check the tightness of wood screws during the break.

CloudSkipper

Good tip. I wouldn't have thought of doing that with wood screws. Thanks.

carrellh

The sheet metal screws commonly used to screw engines to plastic mounts are threaded all the way to the head so I think you should be very safe using the wood screws. I doubt that they will loosen from running your engine but it only takes a few seconds to check them.

Patxipt

If your screws are the countersunk variety, with a conical head, use a washer between the screw head and the engine mounting flange

w8ye

My Feedback: (16)

In my experience,

Wood screws and sheet metal screws tend to back out of wood because of vibration. The wood does not tear - the screw just back out.

A deck screw or drywall/Sheetrock screw is hardened and tends to hold up better

All these screws work very well sunken in the the black plastic motor mounts

In fact a machine screw threed can be tapped directly into a plastic motor mount and the threads hold and the screws never back out. No lock washers needed.

With 1/4-20 nylon bolts, threads can be tapped directly into maple plywood for landing gear and wing hold downs

CloudSkipper

Hmmm. One other time I test mounted an engine on plywood (with bolts) and noticed after several runs that the plywood was getting soft from fuel and/or oil permeating it. Could that contribute to screws backing out?

Anyway, with that experience in mind I did coat the immediate engine area on the wood plank with a thin layer of epoxy.

I wonder if these screws will resist backing out during a run of one tank full... otherwise not sure if I want to try it.

w8ye

My Feedback: (16)

I have a friend that uses wood and sheet metal screws all the time on his make shift trial run boards. Sometimes, they last long enough for his test of the engine the wood does not come apart. The screws screw out if he re-uses the board.

Put epoxy or CA glue in the screw holes will make the plywood hold up better

All Day Dan

My Feedback: (5)

Mr. Cloudskipper, I would advise you to read page 19 of the instruction manual where OS encourages you not to break in the engine in a static test stand. That is sound advice for any of the new modern day engines and OS knows what they are talking about. Mount the engine in you plane and fly it gently for the first few tank fulls. Instead of flying around in circles, do a lot of loops for the best results. Dan.

w8ye

My Feedback: (16)

I like to put an engine on a stand enough to get familiar with it and get the needle valves set.

I also like to see if it is going to run without problems.

I do the rest of the break in in the air on the plane.

Cherokee Flyer

Amen to the short run on the test stand to do the inital setup and insure the needles are close!

L.

Kostas1

Although

i don't reply to your question/-s,

i must comment this from my experience so far!

I always use Socket Head Cap Screws for mounting my engine on a glass-reinforced plastic mount.

But what i do is this.

Mark the engine's bolt pattern on the engine mount
using the Hobbico (i think..) Dead Center Hole Locator.
This has proven to be the best solution for marking the exact hole center of the engine bolt pattern.

The i drill these x4 spots using a small drill bit like 2mm with my dremel tool.

And then i just Tap the hole with the appropriate size, depending on the screws i will use later.

So i tap the x4 holes
and then i simply mount the engine with the x4 appropriate screws ( SHCS's )

I also use x2 washers on each SHCS ,
one that prevents the screw's head to come in contact with the crankcase,
one that provides a bigger surface for my locking nut , to provide it's captive force.

I wish you understood because my english is not so good.

This installation never let me down YET

So,
i trust it on any engine
and i've used this procedure from my OS 40 LA to a 160FX and Saito 120S , currently, on my BH P-36A Hawk!

Konstantinos
Athens/Greece

Lnewqban

Most of wood screws have the smooth part near the screw head.
It is possible that the screws you have are for sheet metal, made of a harder material and sharp threads for self-tapping.

As they fit tight in the holes, and you cannot drill four perfectly parallel holes into the wood block, some tensions may be created for the crankcase, plus some scratching of the holes.

Why not to use the screws for two clamping pieces that would hold each lip of the crankcase against the piece of wood?
See attachment.

w8ye

My Feedback: (16)

I bought a new one of these test stands at a swap meet for $20 so I just use it.

[img]{akamaiimageforum}/upfiles/337908/Om32069.jpg[/img]

nonstoprc

My Feedback: (90)

My experience with using pine board as the base for test stand is that the wood will eventually give in and the screws can back out. That does not happen within one break-in session though. If a denser board (such as the oak board) is used, the screws can hold on really good. The biggest engine I tried is YS110.

Rudolph Hart

I used soft pine and self tapped a dave brown mount on with a saito 115 for break in.Motor was very rich and vibrated it's way airborne after severing the fuel line etc.Very exciting in the confines of a small shed with only a lawnmower to hide behind.

w8ye

My Feedback: (16)

Been there and done that a couple times over the years

NM2K

My Feedback: (14)

Don't use true wood screws. Wood screws utilize a tapered shank and will eventually chip away the wood's threads and loosen. Quite often this happens suddenly and without warning.

Instead, use sheet metal screws, or as the other fellow suggested, deck screws. You want something with a constant body diameter and something made to take some flexing, like deck screws. I usually use sheet metal screws with perfect success.


Ed Cregger

CloudSkipper

After reading more of the advise in this thread, I ordered a clamp down style test stand. It's more basic than the one pictured above, but will be better than the current arrangement.

Thanks for all the input.

Gave me a laugh. Yikes I don't want that to happen