I bought this model from Nitro planes, but the instruction manual is trash....It doesnt specify where exactly to mount the engine and it didnt come with a mounting template.

The plane is the Pitts M12-120.

I will be mounting an RCGF 26cc gasser on it. This is my first gasser and I'm hoping to get some good advise from some members here at RCU.

I hope I attached the picture to this post correctly.

You don't need the manufacturer to provide a template. They don't know what engine you're going to use. Instructions themselves are pretty easy. Center the engine on the firewall where it will be when properly aligned with the cowl and drill 4 holes. First determine how long the engine mounts need to be. Be prepared to make your own.

Now, you can run over to the Wild Hare Forum and open the thread titled "new 35% Edge" and find the post about engine mounting or I can move the entire post over here. Faster if you go over there, but let us know which way to go. The pics are just teasers. The Wild Hare post has a lot of text that I'm not even thinkin' about writing twice.

Text copied from "New 35% Edge" thread in the Wild Hare Forum

I'm going to illustrate my method of centering and mounting engines. It's a bit different because it does not require a kit supplier to have first purchased every imaginable type of engine that could fly the plane, and expended the time and labor to mount them in order to make a template. Easy for the buyers but a royal and expensive PITA for the distributors. Everybody that owns an engine has the ability to make a simple and easy to use template for each of their engine types. More on that in a moment.

Somewhere and sometime in this post somebody is going to ask "What length standoffs do I need?". The answer is the depth of the cowl from the firewall to the face of the cowl ring, minus the depth of the engine from the mounting lugs or plate to the face of the prop hub, plus 1/8". The next question will be something along the lines of "What length standoffs should I buy?" The answer will be: Why do you ask when you can make your own faster, cheaper, lighter, and stronger than any commercially made standoff available?" This post will not make PSP Mfg, SWB, or DA happy at all. 3w won't care because they tell you not to use standoffs anyway. I'll show you a method very similar to what Tom uses for his planes. It's easier and faster than what I normally do for my smaller planes, while being much more supportive than some spindly legged aluminum standoffs. You'll have yours made and mounted before a supplier could get them in the mail to you. Another side to this standoff thing is that you have to bet that someone that's doing their first gasser will browse through this thread thinking they might see something that would help them mount their engine. Hopefully they will find an answer.

No matter what engine you elect to use on any plane, a basic mounting template can be home made out of a length of 3/8" or whatever wood dowel long enough to reach from the firewall through the cowl ring, a piece of 1/8" plywood, and some 1/8" balsa sheet triangle gussets. That's it, that's all, and you have an engine template that can be used on any plane you choose to use that engine on. You only need to determine the engine mounting hole pattern, and determine the relationship of the crankshaft to the mounting holes. Most engines have the crankshaft centered between the mounting holes but a few, such as 3w and 3mm, do not. Those just take a few minutes longer to lay out. See the pics to better visualize how to make a template. A little extra time making a "transferable" engine template saves a lot of time and work later when you assemble other planes that will use the same engines.

Once you have made the template apply some double sided tape to the back of the template. Use that to stick the template on the firewall. It lets you move the template around to find that magic center spot. You may have to stick the template on the firewall before you install the cowl. No biggie since you can still move the template around. If you already have a spinner that fits the cowl ring install the backplate on the template to make centering a little faster. Hopefully you used a wood dowel that is close to the size of the prop mounting hole. When the backplate, sitting on the wood dowel, fits nicely on the cowl ring you've found center. No backplate? Just use a tape measure and shoot for +/- 1/32". Now mark the mounting screw holes and check them for correct positioning, again using the template, one more time before drilling.

Below are engine templates for a Taurus 3.2, Brison 6.4, and a rear induction RCGF 100. For those that don't have table saws there's a picture of a tool you can pick up at any hardware store pretty cheap for making accurate cuts on the engine mount stock.

The wood engine mount standoffs here are 3/4" hardwood square stock available at lumber yards or hardware stores. Costs a couple of bucks. After cutting them to length, center drill them on a drill press. If you don't have a drill press find someone who does. Go slow and don't pressure the bit to prevent bending the drill. That's what makes for center holes that angle away from true center. After the standoffs are installed you can cut some 1/8" ply to connect (glue) the standoffs and make them as solid as the firewall. No need to glue them to the aircraft firewall unless you want to but that makes it a bit tough to change to another engine type at some later date. I prefer the structural rigidity that a "boxed" engine mount provides. No engine twist as you would have with individual standoffs. Nada, nyet, none! You can box the entire mount or simply add a sheet of ply to any pair of legs. No movement at all and much more secure than individual aluminum standoff legs.

The following in italics has been added for those reading this in the Gas Engine Forum

For those new to gas giants there's a tremendous amount of information on how to do most anything in the Wild Hare Forum. Wild Hare has made it their business to introduce new people to gas giants and in so doing set up their forum for their customers to participate in. Just about every new W/H plane coming to market gets it's own "build thread" where various methods of doing most anything are described and depicted. It's to the newbies benefit to spend some time over there reading about what they need to learn to become more knowledgable about the differences between small glow and large gas aircraft and what to do to make it all happen safely and effectively. There's a lot to learn and it's all free. All ya gotta do is peruse the various threads and catch up on some reading.

Cool....The picture came out!!!

Thanks Tired Old Man...Good advise and good pictures to get me started. If you don't mind bringing it here, I would appreciate it!!!

Those templates you made are really AWESOME!!! Did you trace the template using the engine backplate?

I got to make me some of those.

Pretty much, yes. However, when you go back to my first post and read the added text you'll note that some engines will not let you "trace the backplate". RCGF is one of them, as is 3w, DA, and some others. For those you just need to be either be a little creative with some poster board or be real good at geometry. Hopefully you're real good at geometry

The nice thing about the templates using the long dowels is that no matter what the stand off distance is between the engine and firewall, the prop shaft will be properly centered in the cowl ring if the dowel was centered when you marked the mounting holes on the template. So a little extra time spent making sure the template was accurately made will provide for excellent engine mounting every time.

T.O.M.

Geometry.....What the hell is that???I barely made it through Fundamentals in High school.

But on a good note, with all the info you have given me, I'm sure I can come up with something. Without getting math involved!!!

Thanks for all your help!!!

It is hard to tell from the picture but it looks like they have the center thrust line of engine marked on the fire wall.

Milton

roccoym,

You're welcome. You're what it's all about.

Milton,

Never hurts to check. How many times have we seen marks in the wrong places? Discovered to be incorrect after the fact? Kinda fun to also teach them how