Need a tip on how to mark and drill my engine mounts ,I am always a little off. Gets a little fustrating

http://www2.towerhobbies.com/cgi-bin...?&I=LXK378&P=0

great planes dead center hole locator, it works great

Whenever possible.. (some engines it don't work) I put the engine n the mount upside down so i don't have to reach arountd the exhaust port to mark the hole locations.

I generally mark one, drill it and bolt the engine on with that bolt... then mark one on the other side of the engne, remove the engine to drill... bolt it on with 2 bolts now....then do the last 2. With the engine bolted in place... less likely to slip while marking the next hole. (hate it when the engine slips and the holes end up 1/2 dia off from were they belong...)

FHHuber has a good method for mounting, and I'll probably try it next time.

I usually clamp the engine to the mount, then use a piece of music wire with a 90 degree angle bent into one end. I heat the wire with a small torch, then press it down into the engine mounting lug's holes. Leaves a nice divot in the "plastic" mount for the drill bit. Doesn't work very well on aluminum mounts though.
Dennis-

512 CES,

I too use the dead-center hole locater like darryl123 mentioned. If the type mount you're using has the two holes for the nose gear to slip through, you're in luck. Just drill a 5/32 hole in a hard piece of wood (using a drill press to insure 90 deg), then slip a 5/32 wire through the two holes and into the hole just drill in the wood. This allows you to mount the engine mount straight upright so that you can now drill the beams (again with a drill press) where the hole locater drill started the holes.

Hope this helps you in some way, cause these mounts can be aggravating. [sm=angry.gif]

Call me 'too complicated', but being a mechanical designer, and a drafter, I play with numbers, and like dimensions..

Here's what I do (and I havent had a problem yet!) jsut use simple math.. total distance from the firewall to prop, minus prop to front moutning hole, minus distance to rear moutning hole.. Will give you where the holes should be..

You know how far it is from the fire wall to the back of the spinner (or the backside of the prop) DIM 'A' [ 4.25" let's say..]

From the engine's data sheet, you know how far it is from teh backside of the prop. to the front moutning hole DIM 'B' [1.375"]

From the engine's data sheet, you know how far it is from teh front moutning hole to the rear (second) mounting hole DIM 'C' [1"]

You know the engine moutn will mate with the fire wall.

so, the front moutning hole on the engine mount should be drilled at A-B=
[4.25" - 1.375" = 2.875", and the second hole is 1" back from that: 1.875"]

Measured from the back of teh engine mount, measure off 1.875" and 2.875". then divide the beam into equal parts. at teh intersections, is where the hole should be drilled.

add a bit to ensure the prop will clear the cowl / has clearance.


(I've always found that clamping an enguine in place and trying to mark the holes will always lead to problems..)

Or, using the info from the data sheet simply make a template and stick it to the mount with glue stick.

jess