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

Cox fuel tank extender

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

Cox fuel tank extender

Old 03-16-2010, 08:53 PM
  #1  
jsesere
Senior Member
Thread Starter
My Feedback: (38)
 
Join Date: Apr 2003
Location: Salem Oregon WA
Posts: 259
Likes: 0
Received 0 Likes on 0 Posts
Default Cox fuel tank extender

I have a fuel tank extender for a Black Widow that is missing one of the four screws. I believe it was made by Kavan, but I'm not sure. The screw is the standard 2-56 Fillister head but is only threaded at one end. The screw measures 1 1/2" long. Does anyone know where I can get replacement screw?
It doesn't need to be completely threaded if that's all that's available. I have searched the internet without much luck so far.
Thanks
Old 03-16-2010, 10:12 PM
  #2  
Andrew
 
Join Date: Feb 2003
Location: Murray, KY
Posts: 3,201
Received 0 Likes on 0 Posts
Default RE: Cox fuel tank extender

Here is a possible option if you can't locate a 1 1/2" screw.

Get a pack of 2-56 blind nuts and a piece of 2-56 threaded rod (or cut the threaded portion off a 2-56 screw). Since many of the threaded rods are rolled threads, a section of machine screw would probably be better. Run a screw into the blind nut to hold it and using a file or bench grinder, remove the flange leaving a short threaded barrel. You can get fillister head screws, just not in the length you need. Put a shorter screw thru the back plate, use the threaded barrel as a coupling nut and add enough theaded rod to make up the needed length.

You may or may not want to add a little thread locker to the coupling - it may dissolve in the high nitro. If you will give the coupling a light rap to get it slightly out of round, it will hold tighter. Not ideal, but I think workable.

andrew
Attached Thumbnails Click image for larger version

Name:	Fd92102.jpg
Views:	15
Size:	14.7 KB
ID:	1399812  
Old 03-16-2010, 10:50 PM
  #3  
Tee Bee
 
Join Date: Feb 2007
Location: Angleton, TX
Posts: 1,984
Received 0 Likes on 0 Posts
Default RE: Cox fuel tank extender

You might try RTL Fasteners. They've got all kinds of model hardware.
Old 03-16-2010, 11:10 PM
  #4  
ChopperMike
Senior Member
 
Join Date: Oct 2003
Location: Mosinee, WI
Posts: 1,185
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Cox fuel tank extender

I just checked on RTL and they don't have anything over 1" long. I too had a need a while back for some longer 2-56 and had to give up and use something else.




Mike
Old 03-16-2010, 11:14 PM
  #5  
jsesere
Senior Member
Thread Starter
My Feedback: (38)
 
Join Date: Apr 2003
Location: Salem Oregon WA
Posts: 259
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Cox fuel tank extender

I have been all over the internet and also had no luck. Somebody must have made these for Kavan at some point. Does anyone know if they are still in business?
Old 03-17-2010, 12:32 AM
  #6  
build light
Senior Member
 
build light's Avatar
 
Join Date: Nov 2005
Location: Crete, NE
Posts: 2,246
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Cox fuel tank extender

How about using a one inch threaded 2-56 threaded rod from a nyrod or one like it and about quarter to three eighths inch of inner nyrod tube to join to to a shorter length of fillister head bolt that wojuld be easier to find?

Robert
Old 03-17-2010, 12:57 AM
  #7  
ffkiwi
 
Join Date: Jul 2005
Location: Upper HuttWellington, NEW ZEALAND
Posts: 1,577
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Cox fuel tank extender

You obviously didn't look very hard-Microfasteners has 1-1/2" 2-56 machine screws-though not in filister head. They have them in pan head and socket head though-I'd suggest socket head as it will probably fit without having to grind the head diameter down-and you can buy them in lots of 10. The pan heads are in 50's or 100s. See www.microfasteners.com

ChrisM

'ffkiwi'
Old 03-17-2010, 01:14 AM
  #8  
Silvaire
My Feedback: (50)
 
Silvaire's Avatar
 
Join Date: Sep 2003
Location: Napa, CA
Posts: 521
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Cox fuel tank extender

McMaster Carr also carries 2-56 X 1 1/2 machine screws:

http://www.mcmaster.com/#machine-screws/=6934ik

These are slotted round head stainess. You'd probably have to turn the heads down, but then they'd be pretty close in appearance to the original filister head screws. (You can chuck 'em in a Dremel and use a file if nothing more sophisticated is available.)

Edit: I just tried the link I posted and it just gets you to their machine screws in general. You'll have to drill down through the menu to find the 2-56 X 1 1/2 slotted round head stainess machine screws.
Old 03-17-2010, 04:56 PM
  #9  
dckrsn
 
dckrsn's Avatar
 
Join Date: Jul 2008
Location: Centerport, NY
Posts: 132
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Cox fuel tank extender


ORIGINAL: ffkiwi

You obviously didn't look very hard-Microfasteners has 1-1/2'' 2-56 machine screws-though not in filister head. They have them in pan head and socket head though-I'd suggest socket head as it will probably fit without having to grind the head diameter down-and you can buy them in lots of 10. The pan heads are in 50's or 100s. See www.microfasteners.com

ChrisM

'ffkiwi'
I've used 2-56 socket head machine screws from MacMaster-Carr(both stainless and black oxide) on several Pee-Wee and Bee style backplates,
and they fit beautifly with no modifications.
I have a couple of the Kavan extenders, and the included screws are pretty soft. Maybe aluminum?
Regards,
Bob
Old 03-18-2010, 01:18 AM
  #10  
ptulmer
Senior Member
My Feedback: (5)
 
ptulmer's Avatar
 
Join Date: Apr 2003
Location: Brunswick, GA
Posts: 4,867
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Cox fuel tank extender

Maybe I got different screws than Bob did, but I had to chuck them up in the drill and grind a tidbit off the head to get them to seat properly. Got mine from McMaster-Carr. If you are gonna fly 1/2a much, go ahead and order some prop screws in various lengths, too.
Old 03-18-2010, 10:13 AM
  #11  
fritzke
My Feedback: (1)
 
Join Date: Jan 2002
Location: Crystal, MN
Posts: 1,294
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Cox fuel tank extender

I have a Kavan tank extender as well, but the screws I got with it were not correct threads
to fit the Cox crankcase, so I never used it. Other than it ruining the tank, drilling a hole
in the stock tank shell and using an external one seems to be the way to go.
Dave
Old 03-18-2010, 01:51 PM
  #12  
flyinrog
Senior Member
My Feedback: (1)
 
Join Date: Sep 2002
Location: Burlington, NC
Posts: 7,183
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Cox fuel tank extender

I have one, and if yours is like everyother one I've seen it wont matter, it'll leak anyway....Rog
Old 03-18-2010, 04:05 PM
  #13  
fritzke
My Feedback: (1)
 
Join Date: Jan 2002
Location: Crystal, MN
Posts: 1,294
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Cox fuel tank extender

Plus the extra place the extension tube creates for the intake to leak air, another reason to just use an external tank.
Dave
http://www.rcuniverse.com/forum/m_44.../tm.htm#446499
Old 03-18-2010, 05:45 PM
  #14  
jsesere
Senior Member
Thread Starter
My Feedback: (38)
 
Join Date: Apr 2003
Location: Salem Oregon WA
Posts: 259
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Cox fuel tank extender

Thank you to everyone especially to Bob who is going to send me some screws to use.
You gentleman have been a great help.
Joe
Old 03-18-2010, 07:54 PM
  #15  
lildiesel
Senior Member
 
lildiesel's Avatar
 
Join Date: Nov 2005
Location: Cincinnati, OH
Posts: 754
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Cox fuel tank extender


ORIGINAL: Silvaire
These are slotted round head stainess. You'd probably have to turn the heads down, but then they'd be pretty close in appearance to the original filister head screws. (You can chuck 'em in a Dremel and use a file if nothing more sophisticated is available.)
That move counts as state-of-art high tech on my work bench. [8D]

Old 03-21-2010, 10:26 PM
  #16  
Frank Schwartz
Senior Member
My Feedback: (1)
 
Join Date: May 2002
Location: Hendersonville, TN
Posts: 306
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Cox fuel tank extender

The Kavan extensions used to be carried by Hobby Lobby many. many years ago. They worked great! The first ones were aluminum and did not leak. The later ones were/are plastic and do leak.... You might check with H/L and see if they still stock them...or you might check with Sig. Jim Martin, past owner of H/L son married Kavan's daughter (from Germany) and they live now in Montezuma Iowa and work with Sig....
Old 03-22-2010, 12:34 AM
  #17  
build light
Senior Member
 
build light's Avatar
 
Join Date: Nov 2005
Location: Crete, NE
Posts: 2,246
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Cox fuel tank extender

If anyone still has a copy of the 1974 Sig catalog they were in there as well! I remember those Sig Catalogs well. Oly cost three dollars then and came with a three dollar gift certificate good on any order!

Robert
Old 03-22-2010, 02:10 PM
  #18  
Tee Bee
 
Join Date: Feb 2007
Location: Angleton, TX
Posts: 1,984
Received 0 Likes on 0 Posts
Default RE: Cox fuel tank extender

I also experimented with one of these tank extenders a couple of years ago on a Black Widow with frustrating results. Couldn't ever get the engine to run well for long. Seemed to have an air leak in the induction regardless of how careful I was to assemble it with good o-rings. Made some from fuel tubing but they didn't work well either. Ended up setting it back up with the stock tank and the good performance returned.

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 - Do Not Sell My Personal Information -

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.