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Pitts 40. - 6/5/2008 7:29:26 PM   
bertnhank


 

Posts: 30
Joined: 11/24/2006
From: Calver City, KY, USA
Status: offline 		Just started working on my Pitts 40. Only problem is mounting engine mount. No markings to indicate position. Will be using a Saito 56 . Any suggestions.


HM
       Post #: 1

RE: Pitts 40. - 6/5/2008 7:48:46 PM   
opjose



Posts: 5473
Joined: 11/26/2005
From: Poolesville, MD, USA
Status: offline 		Using a ruler mark the vertical and horizontal center points lines.

This will be where the engine camshaft at the tip ( by the prop washer ) should be aligned to.

Now mount the engine on the engine mount temporarily ( I use clamps ) at the correct distance. I put both of the mount "arms" pointing up on a table, and then clamp the engine to the arms at the correct height. BE SURE that the engine is perfectly "square" with the base ( table top ) and sides ( arms )... use a "T" square to get things right. Adjust the engine position until it is perfect.
( at this point you also want to make your engine bolt marks so you can drill these out later ).

Hold the fuselage with the nose pointed straight up. I clamp mine to a table to make it immobile.

Put the engine on the firewall, and center the shaft with your marks. Sight down from "above".

Because of built in right thrust you'll note that the base of the engine will be ofset about 1/4" or less from the marks you made while the camshaft is centered.

Use a Great Planes Center Hole finder to mark the positions for the blind nuts, using the engine mount holes as a guide.

Even if things are not PERFECT most engine mounts have ovoid holes permiting some final adjustments.

Drill out your holes using increasing sized bits, to avoid fracturing the wood. PRESS LIGHTLY as you drill, let the drill do the work.

Test fit the blind nuts to see if the hole is of the right side. If so remove the blind nuts and apply thin CA to harden the holes and surrounding area. Let dry.

Install the blind nuts and "pull" them into the wood using a washer ( sometimes I also add a few nuts ) and a cap screw of the appropriate size. Be sure that the blind nut is almost flush with the wood and it's teeth have dug in.

Affix your engine mount and engine then do the "cardboard" trick to determine where cowling holes and openings will be required.

Have fun.






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Build em'', fly em'', crash em'' and build more.

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RE: Pitts 40. - 6/5/2008 9:06:08 PM   
bertnhank


 

Posts: 30
Joined: 11/24/2006
From: Calver City, KY, USA
Status: offline 		I'll give it a shot, keep your fingers crossed.

I plan on inverting the engine.

(in reply to opjose)
       Post #: 3

RE: Pitts 40. - 6/5/2008 11:05:44 PM   
bertnhank


 

Posts: 30
Joined: 11/24/2006
From: Calver City, KY, USA
Status: offline 		Well, it is on, it looks lined up to , and the cowling looks good. Will cut out for the Saito tomorrow, thanks for the help.


Hank

(in reply to bertnhank)
       Post #: 4

RE: Pitts 40. - 6/6/2008 4:16:17 PM   
opjose



Posts: 5473
Joined: 11/26/2005
From: Poolesville, MD, USA
Status: offline 		Good going!

Now you'll have no problem with any ARF doing this again.



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Build em'', fly em'', crash em'' and build more.

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       Post #: 5

RE: Pitts 40. - 6/6/2008 8:47:50 PM   
bertnhank


 

Posts: 30
Joined: 11/24/2006
From: Calver City, KY, USA
Status: offline 		Now I am at the ailerons. Trying to connect the top and bottom wings, but having a problem. The bottom aileron will push the top one up, but will not travel far enough in a down motion to be effective.

There are two different pics in the book, one shows the clevis on the forward edge of the aileron, one shows it on the trailing edge. I have it on the forward edge. Should it be there or on the trailing edge?


Hank

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       Post #: 6

RE: Pitts 40. - 6/6/2008 9:00:11 PM   
opjose



Posts: 5473
Joined: 11/26/2005
From: Poolesville, MD, USA
Status: offline 		On biplanes the best arrangement is to have the control rod between the top and bottom aileron, be at the REAR of the aileron, and then have the horns on the same side of the aileron.

e.g. both of the horns on top or on the bottom.

So you wonder, how does this work as the aileron itself gets in the way of the rod?

Da Rock posted a great solution to this... check one of the Ultimate threads or the Skybolt threads where he has pictures of his solution.

Another is to insert a cut down horn at the extreme rear of the aileron.

This ( and Da Rock's solution ) makes both ailerons travel equally up and down...


When individual servos are used for each aileron or for the lower ones only, the control horn goes at the front of the aileron.

-

Do your ailerons otherwise move freely up and down on both wings?

You may want to try turning the horns around if you haven't already CA'd them in place.





< Message edited by opjose -- 6/6/2008 9:01:21 PM >

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Build em'', fly em'', crash em'' and build more.

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RE: Pitts 40. - 6/6/2008 9:30:14 PM   
bertnhank


 

Posts: 30
Joined: 11/24/2006
From: Calver City, KY, USA
Status: offline 		Tne ailerons move fine by themselves. I just moved the control horns to the rear of the servos. I will be using one servo on the bottom wing.

This seems to work better. The book calls for 10mm of throw on the ailerons, I have that, but will not know how that setting is on my plane. Or do you have one, and where do you have it set??

Hank

(in reply to opjose)
       Post #: 8

RE: Pitts 40. - 6/6/2008 9:44:39 PM   
opjose



Posts: 5473
Joined: 11/26/2005
From: Poolesville, MD, USA
Status: offline 		For stuff like this I use the "if it looks alright" rule.

For control surface travel, I try to get as much as I can mechanically without compromising mechanical advantage.

Then I'll set my TX to give me the recommended throws for my LOW rates, and everything I can get for my high rates.

If I find the high rates to be TOO high in flight, I can always set this down later.

I know I can land the plane with the low rates set if the high rates are too problematic.

If I recall correctly I was able to get about 18mm of aileron travel or more.



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Build em'', fly em'', crash em'' and build more.

(in reply to bertnhank)
       Post #: 9

RE: Pitts 40. - 6/6/2008 10:17:49 PM   
bertnhank


 

Posts: 30
Joined: 11/24/2006
From: Calver City, KY, USA
Status: offline 		Just moved the control horns to the rear of the ailerons. Found if I faced the bottom one forward and the top one aft, I probably can get 15-20 mm of throw. That is almost double recommended. Will start at recommended for my low, and add a little on the high.

Never ran into this before, but I guess if you put enough of them together, and fool with it long enough, it all works out in the end.
Thanks for the help, if I can help you with anythingm, let me know.


Hank

(in reply to opjose)
       Post #: 10

RE: Pitts 40. - 6/8/2008 2:44:39 PM   
bertnhank


 

Posts: 30
Joined: 11/24/2006
From: Calver City, KY, USA
Status: offline 		On mounting the engine.
Not sure how this will work on other planes, but the Pitt 40 cowling has it's own individual shape, as usual. I followed your directions, and found that I was to low by about 3/8 of an inch.

Finally got it right and found that on THIS particular model, the center left to right was as you said, but the up and down was different than what you said. I fiddled and faddled, and finally came up with the measurement, again on this particular model that the center is found as you said, but the center line of the engine, inverted needs to be 73 mm or 2 7/8" from the bottom of the firewall. This bird has only one flat surface, and the bottom of the firewall is it.

But thanks again for your help, am finding the R C Universe is a pretty good source of help when you have a problem.

I will start checking it out more frequently and see if I can help someone else.


Hank

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       Post #: 11

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