Go Back  RCU Forums > Glow Engines, Gas Engines, Fuel & Mfg Support Forums > Everything Diesel
Reload this Page >

PAW .35 TBR - new bearings and twin needle carb installation

Notices
Everything Diesel Discuss R/C Diesel engines here.

PAW .35 TBR - new bearings and twin needle carb installation

Old 07-02-2011, 08:13 PM
  #1  
fiery
Thread Starter
My Feedback: (2)
 
Join Date: Feb 2002
Location: Hervey Bay Queensland, AUSTRALIA
Posts: 2,995
Likes: 0
Received 0 Likes on 0 Posts
Default PAW .35 TBR - new bearings and twin needle carb installation

3rd July 2011

After much delay my PAW .35 TBR with its new ball races received it's new carb.

It is a generic Chinese twin needle carb, about 6.5 mm rotor bore. Actual choke area is much less due to spraybar. I believe they are supplied with the ASP/SC/Magnum .15 or .21 engines. I bought it from JustEngines in the UK after an enquiry. I wanted a twin needle carb with a shank near the intake size of the PAW, and rotor bore close to the bore on the PAW carb. Great service from Jenny Landells.

The carb spigot was turned down on a lathe about .3 to .4 mm (US: 1/64th?) to fit the PAW's intake boss. A little skim each time, trial fit, return to lathe for a little more off a couple of times, and then the carb fits better than the original. An "O" ring seal as supplied with the replacement carb is installed, but in reality is not needed.

First start did not go smoothly. I had opened the carb HS needle two and half tuns, as it turned out, far too much. Burpp and flood ...

It took me about half an hour with some considerable compression adjustments to get it running more than few seconds. Carb HS needle setting for top RPM running is just under one turn open. Testament to the fact these diesels sip fuel like I sip malt scotch.

Complete success. After setting the LS needle, it throttles better than it ever did on the OEM supplied unit. In fact, the linearity and speed of pick up it would put many glow engines to shame. Someone once told me PAW's could not be throttled to pick up anything near as smooth as a glow engine. That myth is busted.

The photo's below tell the story. The .35 TBR is driving an 11 x 7.75 Dynathrust prop. A pretty big fan with a thick profile for an engine with .5 bhp. However, the PAW swung it with relish. The steady rythmic idle note was a joy to experience. My long term flying friend and retired mechanic (who tuned down the carb shank on his lathe for me) stood there as it idled for fifteen minutes at a steady 2,100 rpm with a huge grin on his face. He set the throttle opening down from the one I took the reading on. And it just kept running, somewhat to our surprise.

My inspiration for this experiment were Martin (AMB) and Dave (Hobbsy). They have both put modern twin needle carbs on large PAW's with success. Martin with Irvine carbs, and I think MVVS for Hobbsy. Their good experiences motivated me to try this experiment. Thanks to you booth.
Attached Thumbnails Click image for larger version

Name:	Tr49947.jpg
Views:	68
Size:	92.7 KB
ID:	1630737   Click image for larger version

Name:	Je10748.jpg
Views:	51
Size:	113.5 KB
ID:	1630738   Click image for larger version

Name:	Ec87647.jpg
Views:	65
Size:	163.8 KB
ID:	1630739   Click image for larger version

Name:	Rm38436.jpg
Views:	82
Size:	101.6 KB
ID:	1630740   Click image for larger version

Name:	Wu61728.jpg
Views:	69
Size:	92.4 KB
ID:	1630741  
Old 07-02-2011, 09:16 PM
  #2  
AMB
 
Join Date: Jun 2003
Location: winter park, FL
Posts: 6,748
Likes: 0
Received 2 Likes on 2 Posts
Default RE: PAW .35 TBR - new bearings and twin needle carb installation

FIERY love the carby cover (for unprotected sex??) then a bunch of little ones running around 06s not a bad idea glad all worked out cheers martin

OH by the way looks like I get a chance to fly really giant scale in a week or so full size Harvard ( AT-6) one of the chaps that come into the pharmacy a commercial pilot
and bats around in this in his spare time said will me let be take a stab at it once up to altitude, well sort of a live buddy box in the back seat would like to see if I can just keep it level
no its not diesel ears muffs a must its noisy with that big radial. it does the warbird shows around here
Old 07-03-2011, 12:09 AM
  #3  
mike109
Senior Member
 
mike109's Avatar
 
Join Date: Jul 2004
Location: Dubbo, New South Wales, AUSTRALIA
Posts: 1,484
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PAW .35 TBR - new bearings and twin needle carb installation

G'day Fiery. Excellent stuff. I used to use a GMS 25 size carby on a Magnum 46 with a diesel head on it. It also throttled well.

To AMB, you lucky basket. I had a go on a "buddy box" full size flight once in a Cessna 150. I was very happy to get back on the ground. The poor old thing could barely climb on a hot day and the young instructor told me he preferred to fly the company's other 150 because it had a better engine. He might at least waited to tell me that when we were back on the ground and not trying to fly over a range of hills with the plane refusing to climb.

Went flying today. Wind was coming from the North over our favourite trees making things quite nasty for light planes. I had one flight, a very lumpy one, and packed up and went home.

Cheers

Mike in Oz

Old 07-03-2011, 03:38 PM
  #4  
Warren B
 
Join Date: Feb 2010
Location: Melbourne, AUSTRALIA
Posts: 68
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PAW .35 TBR - new bearings and twin needle carb installation

I've been flying a plain bearing PAW 35 in my Super Scorpion for a couple of years - a great combination.
I run a 14x6 wood (because I have a lot of them) and it turns this at 6,400 rpm.
Idle is great, never bothered measuring it, but it's very slow -just the original PAW carb, no problems.

Only issue is stopping the beasty. It keep running with the carb closed, just on teh air bleed - and it will do this much longer than my patience lasts.
Standard method is remove the fuel feed - a good party trick as it idles on for anothetr 30 seconds with no connection.

Not a lot of power - but got to love it anyway.
Old 07-03-2011, 05:05 PM
  #5  
fiery
Thread Starter
My Feedback: (2)
 
Join Date: Feb 2002
Location: Hervey Bay Queensland, AUSTRALIA
Posts: 2,995
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PAW .35 TBR - new bearings and twin needle carb installation

Hi Warren

Glad to see your are enjoying your PAW.

I never really had a major issue with the supplied carb. It is the modern PAW "varijet" type. It worked, for all intents, satisfactorily.

Two things annoyed me though:

1./ Fuel inlet fitting moves with the rotor.

2./ No provision for user to adjust low speed mixture for optimum response.

Hence my experiment.

Plenty of users report nothing but good experiences with the factory supplied carb. It is just that I happen to like modern twin needle carbs. My experience is that the throttling performance of the substitute carb definitely exceeds that of the OEM unit.
Old 07-03-2011, 06:12 PM
  #6  
AMB
 
Join Date: Jun 2003
Location: winter park, FL
Posts: 6,748
Likes: 0
Received 2 Likes on 2 Posts
Default RE: PAW .35 TBR - new bearings and twin needle carb installation

Fiery have to agree on that one, maybe back when the PAW was c/l only, they had to come up with a quick fix for R/C but never hit step 2,( welll sort of vari jet) My Indian Sharma PAW knock of although
single needle responds better and the fuel inlet is afixed in its proper location does not rotate martin
I could never get the idle and response right on my PAW 40 before the carb switch
Old 07-03-2011, 08:18 PM
  #7  
Warren B
 
Join Date: Feb 2010
Location: Melbourne, AUSTRALIA
Posts: 68
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PAW .35 TBR - new bearings and twin needle carb installation

Actually my 35 is running the old steel carb, not the Varijet.
As long as the spraybar is correctly aligned I've had zero problems with this carb on the 35, a couple of 55's, an 06 and a 09TBR.
However I agree they are ratrher crude carbs so it's not surprising that better/easier results can be had from more sophisticated carbs.
Old 07-04-2011, 11:57 AM
  #8  
buzzard bait
 
Join Date: Jan 2003
Location: Ithaca, NY
Posts: 3,286
Likes: 0
Received 5 Likes on 5 Posts
Default RE: PAW .35 TBR - new bearings and twin needle carb installation

I've had the same experience as Warren with the old PAW carbs and also with the Varijet...on all of these, the spraybar has to be properly aligned. If it's not, the result is a lousy carb response. Once corrected, they seem to be fine. The problem is I found it very tricky to get it all aligned, screwed back together and tightened up again without throwing off the alignment. Seemed I needed three hands, but have only two.

Regardless, it's great to hear someone enjoying his PAW. I have the 55, 100, 150 and .40.

Jim
Old 07-04-2011, 02:24 PM
  #9  
fiery
Thread Starter
My Feedback: (2)
 
Join Date: Feb 2002
Location: Hervey Bay Queensland, AUSTRALIA
Posts: 2,995
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PAW .35 TBR - new bearings and twin needle carb installation

Gents

Aligning the twin jets in the PAW's carb was the first thing I looked at when seeking to optimise it's performance.

Took me quite a few attempts the first time. The spraybar has to be in just the right position as you tighten up the securing nut.

Old 06-15-2013, 08:34 PM
  #10  
fiery
Thread Starter
My Feedback: (2)
 
Join Date: Feb 2002
Location: Hervey Bay Queensland, AUSTRALIA
Posts: 2,995
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PAW .35 TBR - new bearings and twin needle carb installation

Decided to give it a run. I am considering putting it into service.

http://www.youtube.com/watch?v=yNLCQsQgi94

http://www.youtube.com/watch?v=JGC2RMgQDWA

Cold hand starts are a chore. It wants quite a few choked primes, 3/4's of a turn 'in' on compression; and the main needle opened a turn. Even then it is usually 15 to 30 flicks.

Hot re-starts are easily accomplished. One choked prime, a couple of flicks and it is away.

I recall reading many years ago that Tony Eifflaender, who flew C/L stunt using this engine in early 90's, kept his warm between flights when in competitions by covering the cylinder jacket with a polystyrene foam insulating hood. I can see why.
Attached Thumbnails Click image for larger version

Name:	Ur52329.jpg
Views:	54
Size:	131.5 KB
ID:	1892167   Click image for larger version

Name:	Kf14072.jpg
Views:	57
Size:	126.2 KB
ID:	1892168   Click image for larger version

Name:	Lj22983.jpg
Views:	44
Size:	90.7 KB
ID:	1892169   Click image for larger version

Name:	Yu63773.jpg
Views:	57
Size:	104.3 KB
ID:	1892170  
Old 06-15-2013, 08:47 PM
  #11  
steve111
 
Join Date: Apr 2007
Location: Wollongong, AUSTRALIA
Posts: 393
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PAW .35 TBR - new bearings and twin needle carb installation

Hi Derek, I always found that mine needed quite a few flicks when mounted upright on the bench - seemed like it took a while for the mixture to find its way up into the cylinder. With a sidewinder mounting in a model it was quite different, and would start in one or two flicks using a similar routine to what you describe. I haven't run it for quite a while, though, as it was threatening to shake the model apart.
Old 06-15-2013, 08:54 PM
  #12  
fiery
Thread Starter
My Feedback: (2)
 
Join Date: Feb 2002
Location: Hervey Bay Queensland, AUSTRALIA
Posts: 2,995
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PAW .35 TBR - new bearings and twin needle carb installation

" ... it was threatening to shake the model apart"

The Spiteful?


***

Steve

The engine shown powered my "Detroit Custom Cruiser" old timer type ship. It was side mounted 90 degrees from vertical. In that installation it did hand start acceptably from cold. With this size PAW crankcase charging may not as good as it could be?
Old 06-16-2013, 04:11 AM
  #13  
buzzard bait
 
Join Date: Jan 2003
Location: Ithaca, NY
Posts: 3,286
Likes: 0
Received 5 Likes on 5 Posts
Default RE: PAW .35 TBR - new bearings and twin needle carb installation

I have the .40 but not the .35. The .40 starts pretty quickly from a cold start after a couple of choked turns with the compression increased about like yours. I had mine mounted upright on the bench but now it is sidewinder on a Nieuport 17. Either way it took maybe 10 flicks.

Jim
Old 06-16-2013, 02:22 PM
  #14  
Recycled Flyer
Senior Member
 
Join Date: Oct 2009
Location: SydneyNew South wales, AUSTRALIA
Posts: 1,346
Likes: 0
Received 4 Likes on 4 Posts
Default RE: PAW .35 TBR - new bearings and twin needle carb installation

ORIGINAL: fieryAfter much delay my PAW .35 TBR with its new ball races..........
Hi Derek,
does this engine fit the front race with a screw in ring?

(Perhaps I am entirely mistaken but I seem to remember that the PAW 40 has such a setup.)

And what choice of bearings did you settle on?

Thanks.
Old 06-16-2013, 02:41 PM
  #15  
fiery
Thread Starter
My Feedback: (2)
 
Join Date: Feb 2002
Location: Hervey Bay Queensland, AUSTRALIA
Posts: 2,995
Likes: 0
Received 0 Likes on 0 Posts
Default RE: PAW .35 TBR - new bearings and twin needle carb installation

That is my recollection.

I scourced the replacement races from a local bearing supplier. Unfortunately I did not keep a note of the sizes.

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.