Author Topic: PIPE SETUP ?? (Read 1264 times)

Greg L Bahrman · « **on:** January 31, 2009, 12:15:56 PM »

I got this pipe in a trade. What pipe is it? and what are the the dimensions I should use to set it up for stunt. The engine will be a Ro-Jett 61 or a Ro-Jett 65. Small end is 7/8 in. O.D. large straight section is 1 1/2 O.D. and 7 1/2 long. Exit diameter is 3/8 I.D. From small end to start of the 1 1/2 dia. straight section it is 6 7/8. Pipe total length is 14 3/8 in. Any more measurements or pictures needed, just ask please. Thanks for your help. Greg

Balsa Butcher · « **Reply #1 on:** January 31, 2009, 05:02:58 PM »

Greg: My guess is that it is a Randy Smith or RO pipe - probably the best out there. The important measure is from the plug to the first baffle. Find that by gently inserting a dowel into the front of the pipe and measuring how far it goes in. That is your first baffle. Mark this location on the outside of your pipe for reference. A good measurement to start would be about 17 1/2 inches plug to baffle. Shorter = higher RPM, longer = lower RPM. Adjust to preference. Randy's tuned pipe chart can be found (among other places) on Heman Lee's "Aeromaniacs" web site.

peter jurczyk · « **Reply #2 on:** January 31, 2009, 08:24:34 PM »

Looks like the RO pipe.I run mine 18 1/8 glo plug to baffle.I run the cast case 61.18 1/2 is where i started.Ifly at whittier narrows sometimes

Greg L Bahrman · « **Reply #3 on:** January 31, 2009, 09:09:18 PM »

Hi Pete,
I have seen you fly several times at different contests. What are your launch RPM's at 18 1/8.
Thanks, Greg

Balsa Butcher · « **Reply #4 on:** February 01, 2009, 12:16:11 AM »

Greg: You've got me on that one. My tuna pipe ship is still in the paint shop and hasn't been flown. I've done a lot of bench testing but I'll defer this question to someone with more flight time on their set-up. Check out the previously mentioned tuned pipe chart though, lots of good info.

peter jurczyk · « **Reply #5 on:** February 01, 2009, 09:11:24 AM »

10.300 with 12 1/4 x3 5/8 blue eather 2 blade repitched tips.It works great for me

Eric Viglione · « **Reply #6 on:** February 01, 2009, 02:16:30 PM »

Greg - He is correct, that is an RO pipe I bought new with the motor directly from Richard. ( I think Richards early pipes were made by Eather) I think 18 1/8" to the baffle sounds right (it's been a few years). I think I ran it at 20.5" from the glow plug to the aluminum back plate on that pipe (like I said, it's been a while). Running the longer pipe length with that big pipe, I never had the dreaded flame outs that some people had with that motor in the early days. Don't remember the launch RPM for sure, but 9600-9800Rpm rings a bell on 4 pitch on Powermaster 10/18 Rojett Blend.

I ran a TopFlite Powerpoint wood 12x4 for laughs on that motor in a Staris, and it turned out to be a very good (and CHEAP) prop for that motor to start out with until I found a good carbon prop. Truth be told, the advantage of the carbon prop was marginal. Those low pitch TF prop's are surprisingly good, especially if you clean them up a little.

Enjoy the motor,
EricV

RandySmith · « **Reply #7 on:** February 02, 2009, 01:35:30 PM »

Quote from: Greg L Bahrman on January 31, 2009, 12:15:56 PM

I got this pipe in a trade. What pipe is it? and what are the the dimensions I should use to set it up for stunt. The engine will be a Ro-Jett 61 or a Ro-Jett 65. Small end is 7/8 in. O.D. large straight section is 1 1/2 O.D. and 7 1/2 long. Exit diameter is 3/8 I.D. From small end to start of the 1 1/2 dia. straight section it is 6 7/8. Pipe total length is 14 3/8 in. Any more measurements or pictures needed, just ask please. Thanks for your help. Greg

Hi Greg

That looks like the pipes Windy makes. To determine the lenght you will first need to find out the exhaust timing of that particular motor
. You can as stated earlier use a dowel slid into the pipe to tell where the first baffle or reflective surface is
Regards
Randy

Greg L Bahrman · « **Reply #8 on:** February 03, 2009, 01:36:31 PM »

Thanks everyone,
I contacted Dub Jett on the RO61 and RO65 per Randy Smiths suggestion and he said the exhaust timimg is 137 degrees on these motors. Following Randys suggested pipe chart that makes the suggested pipe length or starting dimension (plug to baffle) at 17.85 in. with a 10,000 RPM launch or 17.50 with a 10,000 to 10,500 RPM launch. Thanks Again............Greg

Eric Viglione · « **Reply #9 on:** February 03, 2009, 02:09:41 PM »

Greg - It might be now, beats me, but that is one of the "original" RoJett .65's I purchased early on in the first production runs. I'll quote from a 2006 SSW thread from the time period shortly after I bought that motor. If you are in doubt, stick a degree wheel on the motor and check for yourself. It's simple enough to do, and Randy can probably describe the procedure better than I (Randy, you watching?).
EricV

Richard Oliver posted on SSW:
"Lets put this to bed. Both engies have the same timing. The CNC machine does not know when it has the 61 or 65 in the jig for cutting ports. The 65 is a larger bore and the mandrel for screwing the liner to the jig is slightly larger to accomadate. The machine still does not know which sleeve is on the jig and the program is the same for both. Timming is 144/128. It was intended to be 136/126. When we made the first engine it turned out to be 140/130.
After flying this for a while I asked Dub to make one that was 4° lower to 136/126. When he programed the new liner he went the wrong way (remember we are making one at a time at this point) and made it 144. Not sure how he got the 130 down to 128 but there it was. Out to the flying field I went and it ran so well I never looked back or even checked it. Jett was told to run with the program in the production run and off I went to my first Nats...<Snip> "

Greg L Bahrman · « **Reply #10 on:** February 03, 2009, 06:11:39 PM »

Well I was wondering how Pete Jurczyk was getting 10,300 at 18 1/8 length. This must be why if the exhaust is 144 degrees ?

The timing is 137 degrees on the exhaust.

Jett Engineering, Inc.
6110 Milwee St. STE J
Houston, Tx 77092 USA
Visit www.jettengineering.com

From: BAHRMANS [mailto:BAHRMAN at SBCGLOBAL.NET]
Sent: Tuesday, February 03, 2009 12:07 AM
To: jettengr
Subject: exhaust timing

Dub,
I am trying to set up a pipes for the RO 61 and the RO 65. If I knew the exhaust timing as in 130 or 135 etc. then I could figure the setup length from the plug to the first baffle in the pipe using Randy Smiths pipe chart. Can you help. Thanks, Greg

peter jurczyk · « **Reply #11 on:** February 03, 2009, 08:41:44 PM »

I dont know what the timing is.but no way could i make the pipe work at 17 1/2 .tried many props fuel & every thing else.minimum pipe length starts at 18. 181/2 very good starting point.I.m just starting to use a PA pipe and it needs abot the same length.Any help i can be just call.dingers got my ph#

RandySmith · « **Reply #12 on:** February 03, 2009, 10:52:46 PM »

Greg

Why don't you just plan on using it at 18.5 to 19 inches and start trying it there first. You have to have exact numbers ,to get exact fiqures, its not hard to move it in and out so trial and error can be a good thing you will learn how it acts at differant lenght

Randy

Author Topic: PIPE SETUP ?? (Read 1264 times)

Greg L Bahrman

PIPE SETUP ??

Balsa Butcher

Re: PIPE SETUP ??

peter jurczyk

Re: PIPE SETUP ??

Greg L Bahrman

Re: PIPE SETUP ??

Balsa Butcher

Re: PIPE SETUP ??

peter jurczyk

Re: PIPE SETUP ??

Eric Viglione

Re: PIPE SETUP ??

RandySmith

Re: PIPE SETUP ??

Greg L Bahrman

Re: PIPE SETUP ??

Eric Viglione

Re: PIPE SETUP ??

Greg L Bahrman

Re: PIPE SETUP ??

peter jurczyk

Re: PIPE SETUP ??

RandySmith

Re: PIPE SETUP ??