Help Needed with a Tower 46
06-07-2003, 11:33 PM
#1
Help Needed with a Tower 46
I've got a tower 46 on a spad the will not run right. It ran great during the first 4 tanks at break in but has gotten worse. It is hard to start and has poor low to high throttle transition. When it stops running I see bubbles flowing backwards from the carb back to the tank. I will run the engine with a different tank tomorrow and see what happens. I searched some old threads and read about people having bad air leaks at the carb. Also saw a new Tower Trainer RTF with the same engine at the field running almost as poorly as mine. It also had bubbles flowing backwards at shutdown and bad low to high trans.
06-08-2003, 04:03 AM
#4
Senior Member
Tower .46
RVator,
If you broke your engine in correctly, 2 10 ounce tanks should be enough. Read this and compare:
http://www.rcuniverse.com/showthread...59&forumid=145
Also, if your tank centerline is lower then the middle of the spray-bar, in your carburettor, or whenever the fuel level is lower than the spray-bar, you will have fuel flowing back with bubbles.
When flowing back to the tank, the carburettor can only flow air.
If you have bubbles in your fuel line when the engine is running, you should find the source of the problem.
In any case, since your plane is a tail-wheel design, your tank centerline should be a little higher (1/4-3/8")than the middle of the spray-bar, to compensate for the nose-high attitude.
THIS IS IMPORTANT AND IN MANY KITS AND ARFS, OVERLOOKED.
Did you bother to adjust the setting of the idle needle???
Many modelers, not only beginners, expect to overcome all their maladies, by adjusting only the high-speed needle.
The idle needle is there for a reason. No engine can be expected to idle and transition, without touching this idle mixture adjustment. It is usually set too rich, so try readjusting it.
You can read elsewhere how to do it, or ask..
If you broke your engine in correctly, 2 10 ounce tanks should be enough. Read this and compare:
http://www.rcuniverse.com/showthread...59&forumid=145
Also, if your tank centerline is lower then the middle of the spray-bar, in your carburettor, or whenever the fuel level is lower than the spray-bar, you will have fuel flowing back with bubbles.
When flowing back to the tank, the carburettor can only flow air.
If you have bubbles in your fuel line when the engine is running, you should find the source of the problem.
In any case, since your plane is a tail-wheel design, your tank centerline should be a little higher (1/4-3/8")than the middle of the spray-bar, to compensate for the nose-high attitude.
THIS IS IMPORTANT AND IN MANY KITS AND ARFS, OVERLOOKED.
Did you bother to adjust the setting of the idle needle???
Many modelers, not only beginners, expect to overcome all their maladies, by adjusting only the high-speed needle.
The idle needle is there for a reason. No engine can be expected to idle and transition, without touching this idle mixture adjustment. It is usually set too rich, so try readjusting it.
You can read elsewhere how to do it, or ask..
06-08-2003, 04:38 AM
#5
RVator....
....try removing the front fuel nipple....and sealing it
with blue Lock-Tite (thread locker) or JB Weld....
....the threads on the nipple are course....and can be
sloppy....giving way to an air leak....and the bubbles.
Loosen, twist....and push the carb down tight against
the o-ring....and cinch it down again....
Dave.
with blue Lock-Tite (thread locker) or JB Weld....
....the threads on the nipple are course....and can be
sloppy....giving way to an air leak....and the bubbles.
Loosen, twist....and push the carb down tight against
the o-ring....and cinch it down again....
Dave.
06-08-2003, 09:05 PM
#7
Help Needed with a Tower 46
Thanks everone for the help. My spad does sit very noes high on its homemade gear "like a Harmon Rocket" . I do plan to change the gear. I put RTV on the fuel nipples and changed the O-ring on the carb base. Then I ran it with another tank tie rapped to the fuselage. I then adjusted the low and high needle and finally got it running good. After that I hooked the fuel lines back to the original tank and started it up. Now I see bubbles in the lines as it is running. I guess with the other air leaks up front it never pulled hard enough to show up before. Now I will replace the tank and go fly next week. If it ever stops raining.
06-09-2003, 02:56 AM
#8
Senior Member
Air bubbles
RVator,
Air bubbles can also be a result of vibration. The tank clunk jumps up and exposes itself to air, which ends up in the fuel line.
Is your fuel tank completely wrapped in latex foam and not in direct contact with any part of the airframe?
It takes no more than a 1/4" of latex foam to insulate.
Also, fabricate a latex foam nose ring to insulate the tank nose from the firewall.
Remove the installed tank, install it outside and see the source of the bubbles. Maybe it is a pinhole after all.
Sincerely,
Air bubbles can also be a result of vibration. The tank clunk jumps up and exposes itself to air, which ends up in the fuel line.
Is your fuel tank completely wrapped in latex foam and not in direct contact with any part of the airframe?
It takes no more than a 1/4" of latex foam to insulate.
Also, fabricate a latex foam nose ring to insulate the tank nose from the firewall.
Remove the installed tank, install it outside and see the source of the bubbles. Maybe it is a pinhole after all.
Sincerely,
