Go Back  RCU Forums > RC Airplanes > "1/2 A" & "1/8 A" airplanes
Reload this Page >

Pee wee tank overheating.

Notices
"1/2 A" & "1/8 A" airplanes These are the small ones...more popular now than ever.

Pee wee tank overheating.

Old 11-16-2011, 11:31 PM
  #1  
Rendegade
Senior Member
Thread Starter
 
Join Date: Mar 2003
Location: Perth, AUSTRALIA
Posts: 1,881
Likes: 0
Received 0 Likes on 0 Posts
Default Pee wee tank overheating.

I've heard this quite a bit, and I'm curious if there's any truth to the matter, and if so, are there any fixes?

I wouldn't mind running a tank out on my pee wee's once in a while!
Old 11-16-2011, 11:47 PM
  #2  
combatpigg
Senior Member
My Feedback: (3)
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 20,388
Received 26 Likes on 24 Posts
Default RE: Pee wee tank overheating.

If you do a thorough tear down of any 1/2A engine and do a step by step reassembly starting with a sonic cleaning of all parts then detailing the crankshaft's fit in the case, you will solve a good percentage of run away heat buildup issues. Chuck the very tip of the crank into a drill press, lathe, etc., and polish the main journal with 800 grit or finer paper. Do not go a billionth of an inch overboard doing this, do lots of trial fits to see how well the crank spins with just the flick of the prop.
Check the fore and aft clearances of the prop drive assembly.
As you reassemble the engine the fits of all inter-connected parts need to be checked and looked at under magnification, especially the piston / liner.
Look for gouges, ridges, bumps, shiny wear marks on the piston, etc.
Just a cheap jeweler's lens will reveal lots of nasty stuff sometimes.
Old 11-17-2011, 12:02 AM
  #3  
Mr Cox
 
Mr Cox's Avatar
 
Join Date: Jul 2007
Location: Karlstad, SWEDEN
Posts: 3,791
Likes: 0
Received 2 Likes on 2 Posts
Default RE: Pee wee tank overheating.

I was struggling to get consistent runs from my peewee, it would only empty the tank if I compensated a little on the needle throughout the run. I tried different props and head shims etc. but didn't manage to solve it. To me that was related to the heating of the tank simply because it is attached to the crankcase. Mine didn't have a particularly tight crank (quite the opposite) or any other problems that I could see.

I was going to try an external tank (which works well on the Babebees) but I never got around to do that. Instead I converted it to diesel and now it empties the tank everytime. Disels are less sensitive on the needle, they can miss but don't stop, but the engine also runs a lot colder.

One thing one could to try, without drilling a hole in the the stock tank, is to put one of the yellow helicopter backplates on it and see if the needling problems go away with an external tank.
Old 11-17-2011, 11:44 AM
  #4  
BMatthews
 
BMatthews's Avatar
 
Join Date: Oct 2002
Location: Chilliwack, BC, CANADA
Posts: 12,425
Likes: 0
Received 22 Likes on 19 Posts
Default RE: Pee wee tank overheating.

The first thing, of course, is to make sure the fuel pickup goes all the way to the bottom of the tank bell.

The other is that these engines need a blast of air over them to keep the tank cool. I've seen two cases of close cowlings with Baby Bee's that led to the fuel in the tank boiling.

If it's an exposed engine then it would imply that the crankshaft is too tight in the case and the fitting described by Combat Pigg should solve the issue.
Old 11-17-2011, 02:45 PM
  #5  
Mr Cox
 
Mr Cox's Avatar
 
Join Date: Jul 2007
Location: Karlstad, SWEDEN
Posts: 3,791
Likes: 0
Received 2 Likes on 2 Posts
Default RE: Pee wee tank overheating.

I had planned to have a cowl around the tank area but I never got that far, given the running problems I had. Might still try the external tank though, I should have one of the helicopter backplates somewhere.

Has anyone ever tried to put an intake throttle/choke on the PeeWee, a small conical rod in the intake connected to a servo might do it?
Old 11-17-2011, 06:20 PM
  #6  
skaliwag
My Feedback: (1)
 
skaliwag's Avatar
 
Join Date: Jan 2003
Location: Corralitos CA
Posts: 2,469
Received 2 Likes on 2 Posts
Default RE: Pee wee tank overheating.

Havn't tried to choke a Pee Wee, the ring work fine. Did make a new back plate using the TD 010 venturi drilled out a little. Sent it to a former subscriber for evaluation and never saw it again.
Old 11-17-2011, 07:23 PM
  #7  
Rendegade
Senior Member
Thread Starter
 
Join Date: Mar 2003
Location: Perth, AUSTRALIA
Posts: 1,881
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pee wee tank overheating.

Before I fly again, I'll be sure to wear some xray specs and check the crank fit before flicking myself to death again.

Incidentally, the engine is all out in the breeze as I managed to snap the cheek cowls almost every time I started it!
Old 11-17-2011, 09:01 PM
  #8  
DeviousDave
Senior Member
 
Join Date: Feb 2007
Location: , MI
Posts: 1,781
Likes: 0
Received 1 Like on 1 Post
Default RE: Pee wee tank overheating.

Don't forget to deburr the threaded tank mounting holes on the crank case and deburr the mating holes on the tank. RTV will confirm if it's an air leak, temp related or otherwise by applying to the tank/case junction and the backplate/tank interface.
Old 11-18-2011, 07:41 PM
  #9  
aspeed
 
aspeed's Avatar
 
Join Date: Jul 2011
Location: Ruthven, ON, CANADA
Posts: 3,460
Likes: 0
Received 7 Likes on 7 Posts
Default RE: Pee wee tank overheating.

I found on the Baby Bee's at least that the crankcases were too sloppy after a while and they wouldn't hold a setting.  This would give an inconsistant run, rich,lean,rich lean.  This could cause it to run hot.  As the fuel runs low, it will not cool the tank as much too.  I found if you pull the crank forward and try to rock it up and down with the prop, and there is slop with the piston moving up and down, that is the culprit of an uneven run.  Assuming a good o ring and reed etc. If you have the crank out there is a half moon wear spot at the bottom of the crank bore near the back that is the giveaway. I really don't like to run the reedy ones anymore.  Too much maintenance for air time.  I made a couple of cases with bushings to solve this and it helped.  So would a new case.  I wouldn't lap any cranks myself. It just speeds up the wear cycle.
Old 11-18-2011, 11:08 PM
  #10  
combatpigg
Senior Member
My Feedback: (3)
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 20,388
Received 26 Likes on 24 Posts
Default RE: Pee wee tank overheating.

That's a good point.
If the crank fit is already worn out, you don't want to lap the crank.......
The only .020s I've had my hands on were too tight.
Regardless, the heat from a good running engine, [even a screamer] should never be enough to make the tank hot enough to fry an egg.
The smaller these engines are, the more perfect everything needs to be.
Old 11-19-2011, 02:00 AM
  #11  
Big Al-RCU
Senior Member
 
Big Al-RCU's Avatar
 
Join Date: Feb 2003
Location: Slidell, LA
Posts: 501
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pee wee tank overheating.


ORIGINAL: combatpigg
a good running engine, [even a screamer]
What’s the secret to get a good consistent strong running Pee Wee? I’ve never been able to get a good run on a Pee Wee. My first (and admittedly pretty much last) one was on a R/O (over weight) School Boy back in about ‘69. The original .010 was just barely able to keep it airborne. Bought a new Pee Wee and there was no noticeable change except that it wouldn’t hold a consistent needle setting for the full run. (Never considered tank heating, but that may have been a contributor?) Installed a Tee Dee .020 and problem solved. Night and day.
Al
P.S. As an aside my School Boy was overweight due to the available radio gear of the time. When Ken Willard designed his School Boy, Page Boy, etc. he was able to use super-regen receivers on the citizens band such as the postage stamp sized Otarion. (Believe it or not, they were comparable weight wise to our modern micro receivers). The upsurge of the CB users soon rendered super-regen receivers useless for R/C. Thus my selection of the new (at the time), but heavier, Ace super-het double-ended reciever and Adams actuator which comes in at 2.96 oz (I still have it and just weighed it). As a comparison; with modern micro R/C gear an all up weight of 4 to 4.5 oz for an entire .010 model with two or even three full proportional channels is the norm.
Al
Old 11-19-2011, 05:13 AM
  #12  
Mr Cox
 
Mr Cox's Avatar
 
Join Date: Jul 2007
Location: Karlstad, SWEDEN
Posts: 3,791
Likes: 0
Received 2 Likes on 2 Posts
Default RE: Pee wee tank overheating.

Mine didn't get particularly hot, in the sense that it would boil the fuel. But on a cold day there is a substantial change in the temperature of the crankcase (and the tank) from the start till the end of the run. On the ground I could run the tank out if I fiddled a little with the needle after about half the run, it was very small changes but it was enough to not be able to have a sweet run from the start till the end. Any other problems, like a leaking o-ring on the venture etc will of coarse add to the problem and make it even worse.

It just feels like it is very sensitive on the needle, and the temperature change of the tank just makes it even worse. I have had similar problems on a Babe bee and it ran much better on an external tank, i.e. giving very consistent and long runs.
Old 11-19-2011, 11:51 AM
  #13  
combatpigg
Senior Member
My Feedback: (3)
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 20,388
Received 26 Likes on 24 Posts
Default RE: Pee wee tank overheating.

Any engine that cant handle subtle changes in fuel head pressure is deficient in the basic things that promote spontaneous combustion from start to finish.
Compression......good compression also promotes good fuel draw
Crankcase seal.......directly effects fuel draw and pumping action
Friction free and smooth operation of the moving parts
Condition of the fuel and the glow plug
Plumbing problems, including the critical seal between the built in tank and the air intake passage.
A tired engine can have extra time squeezed out of it by running less prop, no head shims and up to 30% oil and bladder pressure. De-pitch the .020 prop by twisting it with your fingers.

I don't use the built in tank for RC applications as a general practice. All it is to me is a motor mount.
I'm happier with the results of using a remote fuel tank for RC projects.
Old 11-19-2011, 01:04 PM
  #14  
combatpigg
Senior Member
My Feedback: (3)
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 20,388
Received 26 Likes on 24 Posts
Default RE: Pee wee tank overheating.

Al, if the engine was in good shape you could always try more oil and less prop. Just scrape some mass off the fat part of the plastic blades with your exacto knife, trim a tiny amount of diameter off, de-pitch the blades a little.
I expect all engines to pass some sort of a leakdown test. If you duct tape the exhaust ports and rig up a hose to force air into the intake, you shouldn't see leakage around the head or the snout of the crankcase. Turn the engine over slowly and observe. It helps to have the engine in water to see where the air bubbles are coming out. I know a guy who owns a small engine shop who can quickly plow through a barrel full of weed eater engines with this test and evaluate the ones that are worth spending time on and the ones that are useless junk.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.