Before moutning my firewall, I wanted to drill all the holes for the Mount.

I have been able to find the center position on the firewall, but need to know how to center the Mount. I have the OS .61 Engine and matching mount.

The instructions say there are 3 markings, but I can only find one.

Also, Should I or do I have to cut out hte center hole in the Firewall? I assume I should so I can run the fule lines and or poke the thank out of it if need be.

Thank you for you help.

Gary...

What brand motor mount do you have?

Eyballing it is close enough. You want to get it centered left and right the best you can but up and down depends on the engine, if there is a cowl, etc. on most mounts the top of the mount arms(where the engine sits on) should be the center of the firewall. As for the center of the firewall, you only need to cut as much as needed. I just drill whatever holes I need for the fuel lines, throttle. I'm sure some people do it different. Keep in mind you not going to the moon with these things. Just make sure its safe.

Eyballing it is close enough. You want to get it centered left and right the best you can but up and down depends on the engine, if there is a cowl, etc. on most mounts the top of the mount arms(where the engine sits on) should be the center of the firewall. As for the center of the firewall, you only need to cut as much as needed. I just drill whatever holes I need for the fuel lines, throttle. I'm sure some people do it different. Keep in mind you not going to the moon with these things. Just make sure its safe.

Gary it is important to properly put the engine on the thrust line of the model. As far as centered left to right that is dependant on whether the firewall has right thrust or not and whether it has a cowl that you need to keep the crankshaft centered in.
Which model are you building and what brand motor mount do you have.

sp. edit

I am building the Skyshark SBD Dauntless and using the OS .61 Max along with the matching OS .61 Mount.
I building directions call for drawing a horizontal Line .10 of an inch to the right of center to offset the thrust. AND Yes it does have a cowl that Iwill need to gut for Glow Plus Access and cooling.

Thank you again everyone.

Gary...

The instruction to draw a vertical line .10 of an inch to right of center is because the firewall will have right thrust built in and moving it over should insure that the crankshaft is centered in the cowl. There should be a datum line drawn on the plans for the center line of the crankshaft. If you are mounting the engine inverted the beam where the engine will bolt should line up on that datum line. Or in other words, the bottom of the engine mounting lugs should line up with that line.
If this is not clear or if you have any other questions ask away.

"Eyeballing it" is not, NOT, NOT "close enough". It's either right or wrong. The thrust line needs to be where the plans call for it to be.

Gary, do it the right way. Since you can't find datum points on the mount, you can locate the mount in one of two ways:

1. Measure each side of the mount (assuming it isn't round) and mark your own datum points.

2. Measure from the outside edges of the mount to the corresponding edges of the firewall. Adjust the position of the mount until it's located where it should be according to the plans.

Dr.1

Sure it is. I mean if you can do it properly. I don't know it I've ever sat there and took hours drawing lines. I did say it did depend on a couple of things such as if he had a cowl, etc. But I've built all my models this way and never had a problem. Like I said, some people probably don't do it this way. But it will fly just as well as long as its close.

The top of the rail on the engine mount should be on the thrust line

"eyeballing" an engine location is NOT doing it "properly". The manufacturer put those lines on the plans for a reason, you know. You build it your way, ryan, I'll build it right. And it doesn't take "hours". 15-20 minutes should be plenty of time to measure and mark.

Dr.1

I don't think I ever cut your way of doing it down, so I don't see the need for you to cut mine down. Just a thought, there is more than one way to do things. Both ways are proper. Like I said, some do it my way, some do it yours. NOT A BIG DEAL.

Thank You EVERYEONE....

Being New to this is sometimes a drawback but I know it is part of the learing curve.
There were no Datum Lines Draw on the part of the plans that were face on to the firewall. BUt I could see where the Engine attached to the Mount and Draw My own.

I am happy to say I was right on with my measurements and the .10 of an inch is where the Center of the prop Should Be.

I will attach a link to my build in a few days.
Thanks Again
GAry...