BECKERFLY

getting ready to build motor box for aw 29% edge, mounting a brison 3.2 from firewall to end of cowl is 7.25 in. from engine backplate to spinner backplate is 5.375 in. i am building eng box out of 1/4" aircraft ply. my question is according to my math the eng box should be 2" long, to compensate for 2 deg right thrust i am guessing the left side of mount should be 1/8" longer. if this is correct how far should the offset be on mount to line up properly on centerline?? p.s. you can tell i'm no math wiz.

BigBirdFlyer

My Feedback: (13)

:idea: I think you have the right idea. If your measurements are taken from the firewall to the front of the cowl, with the cowl installed. Allow about 1/16" clearance at the front of the cowl for the spinner backplate. 1/8" longer on the left side = about 2 to 3 deg. for right thrust.
Use a square to make sure that the firewall is flat and doesn't have any built in thrust.
Yoy will enjoy that engine combo.

BECKERFLY

Bigbird Flyer,
thanks for the reply, i waited all day for this one now i can go home tonight and plan the mount.


Thanks!!!

BigBirdFlyer

My Feedback: (13)

Glad to help.

Wings-RCU

My Feedback: (2)

Beckerfly, thought you would like this (a brisson 3.2 on a 29% AW Edge

BigBirdFlyer

My Feedback: (13)

:spinnyeye The Brisson 3.2 is a great engine for the 29% edge. A friend of mine is building one now.

krayzc-RCU

My Feedback: (31)

Wings:
I love your choke set-up!

I have my 2 brisons on a DP Extra and a 29% AW Edge. I need to pick up that 90 degress servo arm deal you have so i can run me chokes on both of the above planes. R U using the gear channel for these set-ups?

PS my firwall is built the crude way i have a 2 x 4 cut out the correct size, then i took a door hold saw & mowed out the center and added a piece of plywood to give the the final correct thickness very quick for me to do. i think the ply is around 1/4 and i think a 2 x 4 is short the 2 part by about 1/4- 3/8 of a inch can't rember the exact figures.....

rhakkenberg

What you need to do now is get rid of the mechanical advance and go with a C&H ignition. It is truly a good upgrade for this motor. Many reasons for that comment; one of which is the Teflon ring is seldom perfectly round. If you fly in cold temps the ring and engine casing will expand and contract from the basement to outside. Outside in cold temps the ring tends to bind. Also use lock tight everywhere, on the plane, servos, and the bell crank for the throttle. If using a Bison muffler, check the flange area every 15 flights for stress cracking. I have lost three mufflers. At one time the manufacturer suggested a support strap around the can mounted to the fire wall. this engine is a shaker don't kid yourself. You need to really batten down the hatches because the performance of this moor is fantastic. When broken in, starts on the first flip after a flight.
Rich

krayzc-RCU

My Feedback: (31)

rhakkenberg
how can one tell which system you have?
what is the average cost of the upgrade?

i have over 255 on one of my brison and i have not had to tighten or replace any lost bolts maybe humm. talk at you sooonnnn

Wings-RCU

My Feedback: (2)

rhakenberg,
It is a C&H ignition with mechanical advance. I assume you are talking about going to the electronic advance to get rid of some of the linkages. C&H claims there is no performance advantage by going to electronic advance and it also eliminates your ability to customize your advance. So, unless you’re having problems with the linkages I can't see a reason to change. Like krayzc I have never had any problems in over two year of flying.

Krayzc
I used one of those fat futuba servo arms that you never use for anything and cut off two of the four arms. I stuck a brass servo eyelet in the center and screwed it to the firewall box. I use a mini servo and run it from a rotary knob on my transmitter. That way I can give it as much or as little choke as I want and it works great as a remote kill.

WarpedWing

My Feedback: (3)

The Brison 3.2 is absolutely perfect for the 29% Edge. I'm really impressed with the Brison 3.2, wonderful engine, terrific power and reliability. I will echo the previous post about this engine being a shaker. Make sure you secure/double-secure your connecting rod to the throttle bellcrank. Mine failed at low altitude and caused the loss of a 28% scale CAP. I love the choke/servo setup shown here. Gotta try that on the next plane I put my engine on.

flyindoc

My Feedback: (8)

Beckerfly,

There is actually a formula to calculate how much offset from the centerline you need for a give amount of right thrust. There are variables you must know. They are backplate to prop washer distance and thrust desired. Here is the formula. I use it all the time and it has never failed me yet. Thank god for the scientific calculator on the computer.


D X tan(A) = O

D = firewall to propwasher distance
A = degrees in thrust you want
O = the amount of offset you will need on the firewall from the centerline to keep the prop shaft centered.

Hope this helps.

Andy

BECKERFLY

Flyindoc,

thanks you bet it helps i will try it this evening.

krayzc-RCU

My Feedback: (31)

i am gettting 7000 on a 22 x 8 mezn what kinds of # are you all getting....?

rhakkenberg

I think with the 22x10 it spins 6800 to 69 if I remember correctly. I originally had on a 20x10 and running 7400 but 7000 seems more appealing. I do use a scimitar design menz which may account for the higher rpm I describe. I have a few inches of snow on the ground. I want to get out and fly or fish.
I'm getting tired of looking at my planes and not flying.
Rich :boxing: