Hi guys,

Working on a CMP Zero 82" build , and my first time adjusting offset. Initially I cut the supplied motor box which had the thrust angle built in, but I wasnt happy with my cuts so I am building a new Spacer/motor box mount. But I have 3 questions before I start drilling wholes in my firewall.

1) Where is the usual place to place the washers to add thrust angle? Between standoffs and spacer/motor box/firewall, or between Engine and Standoffs?

2)looking at the DLE 55RA.
PDF of dimensions: http://milehighrc.com/Manuals/dle55ra-dimensions.pdf

For figuring engine offset... the tool / equation I am using asks for Engine Length. Should I use the length given with the included stock standoffs (171mm which I am using) or without them (103mm) ? I want to say I need to use the 171mm if I plan on placing the washers between the standoffs and motor mount/spacer/firewall???

3) For determining the amount of space to add for a given thrust angle, I use the distance between mounting wholes. The DLE 55RA has two top mounting wholes 90mm apart and the bottom two mounting wholes are 70mm apart. This means I will have / need 2 different measurements for top and bottom washers/shims s to add correct? This is IF all I need is 2-degrees right thrust.???

Thanks!

first, don't over complicate it. all you need is a sheet of paper, a pencil, and a 50 cent protractor. the shims can go behind the standoffs so they shim the standoffs from the firewall. you can use washers, ply, or any combination thereof. thrust offset should be between 2 and 3 degrees..no sense obsessing trying to make it perfect, it's a warbird.

Using a sheet of paper draw a line parallel with the width that will represent the firewall. measure the distance from the firewall to where the prop hub needs to be. We'll call that A. Draw a centerline perpendicular to the firewall and place a mark at A.

Using your protractor draw a 3 degree line towards the firewall using A as the vertex and the centerline as 0. Where that line intersects the firewall will establish the offset from the centerline. probably about 1/4" or so. The 3 degree becomes the actual thrust line and is used to establish the mounting location for the engine.

don't sweat the difference between the distance of mounting lugs, I am sure that it is inconsequential when making shims.

if you can post a picture of your drawing I can answer any questions, but once you see it in front of you you'll probably agree that it's pretty straightforward.

good luck,

Paul

you know what though.... you probably explained the easiest most clearest method for doing this without equations.

OK so, how about shimming , am I right that since the mounting wholes top is wider than the bottom, I'm going to have two different measurements for them to both give me my 2 degrees

With standoffs as they are considered part of the engine lenght. Glad to help. FWIW, I plugged in some numbers on the site and I am not trusting their numbers, as they appear to be about twice what I have seen in practice. I would draw the picture to be sure.