Author Topic: DO-335 (Read 10106 times)

John Rist · « **Reply #50 on:** March 13, 2014, 04:42:34 PM »

I now have two working 1/2A engines for this project. I picked up a TD .051 for $10 bucks. Rolin picked it up at a swap meet for me. Bench test produced 20K rpm on 25% fuel, 5x3 3 blade Cox prop. Today I built a test stand so I could test run my Norvel .061 driving the U-joint/prop shaft assembly. Bench test also produced 20K rpm on 25% fuel, 5x3 3 blade Cox prop.

Fred Cronenwett · « **Reply #51 on:** March 13, 2014, 08:45:44 PM »

John - Your 1/2a will be in the April 2014 issue of Model Aviation. 1/2a will be covered in the next issue

Like the test stand with the shaft drive

Fred

wwwarbird · « **Reply #52 on:** March 13, 2014, 10:21:15 PM »

John,

Can we see a good close up photo (or photos) of how the shaft is designed at the prop mount?

John Rist · « **Reply #53 on:** March 13, 2014, 10:58:28 PM »

Quote from: wwwarbird on March 13, 2014, 10:21:15 PM

John,

Can we see a good close up photo (or photos) of how the shaft is designed at the prop mount?

Attached is the drawing I sent to Lee Machine Shop that was used to create the current shaft. However Lee made the actual shaft from an aluminum tube to save weight.

The prop shown in the test stand picture is a normal prop to provide cooling for the test run. The prop for the airplane is a pusher. On the airplane the rear motor is cooled by prop wash from the front motor.

Avaiojet · « **Reply #54 on:** March 14, 2014, 11:05:12 AM »

John,

Nice design, wish I had thought of something like that.

Will Hinton · « **Reply #55 on:** March 14, 2014, 02:57:09 PM »

Gotta tell ya, John, your engineering skills are fantastic on this. Can't wait to see it fly!

wwwarbird · « **Reply #56 on:** March 15, 2014, 08:19:30 PM »

Quote from: John Rist on March 13, 2014, 10:58:28 PM

Attached is the drawing I sent to Lee Machine Shop that was used to create the current shaft. However Lee made the actual shaft from an aluminum tube to save weight.

The prop shown in the test stand picture is a normal prop to provide cooling for the test run. The prop for the airplane is a pusher. On the airplane the rear motor is cooled by prop wash from the front motor.

Thanks John. Does it use a stock Cox prop thrust washer or...?

John Rist · « **Reply #57 on:** March 15, 2014, 10:47:27 PM »

Quote from: wwwarbird on March 15, 2014, 08:19:30 PM

Thanks John. Does it use a stock Cox prop thrust washer or...?

Yes it is a Cox prop thrust washer. The bearing is from McMaster-Carr. The PN on the package is SRW4ZZ A5. McMaster PN 57155K388. It is a .250 ID, .6250 OD. The outer race is .1960 wide. However the inner race is raised. It is .2272 wide. This allows the bearing's inner race to be hard clamped to the shaft. It is wedged between the prop washer and the shoulder on the shaft. It is double shielded and pre-lubed. However I have had bearing failures until I started adding a drop of oil before each flight. Also they are cheep so I tend to install a new one right before a contest.

wwwarbird · « **Reply #58 on:** March 16, 2014, 07:28:28 PM »

Thanks for the info John, I've been kicking around an idea for a few years for which I would need a reliable shaft setup. I would be needing it for a .15 or a .25 size engine.

John Rist · « **Reply #59 on:** March 17, 2014, 12:25:18 PM »

Quote from: wwwarbird on March 16, 2014, 07:28:28 PM

Thanks for the info John, I've been kicking around an idea for a few years for which I would need a reliable shaft setup. I would be needing it for a .15 or a .25 size engine.

The hard part is the U-joint. I bought mine 2 years ago on Ebay. I have been looking and can not find anything listed anywhere comparable in size. Every thing listed today is for small eclectic boats or for flex shafts. The motor side of my joint has a 1/4 x 20 thread. Lee plugged it and re-threaded for the Norval .061 shaft. If anyone knows of a source please list it.

MarcusCordeiro · « **Reply #60 on:** March 18, 2014, 01:10:40 PM »

Nice!!

Marcus

John Rist · « **Reply #61 on:** March 28, 2014, 01:01:04 PM »

Quote from: wwwarbird on March 16, 2014, 07:28:28 PM

Thanks for the info John, I've been kicking around an idea for a few years for which I would need a reliable shaft setup. I would be needing it for a .15 or a .25 size engine.

Just for fun I ordered the U-joint I found on eBay.

http://www.ebay.com/itm/380691644809?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

It looks like that it could work with a 15 to 25 size engine. It measures about 1.3" long. The motor side has what appears to be a 5mm x .8 bolt hole. Adapting this to your motor could be interesting. Of course if you have a 5 mm motor shaft all is good. If the motor shaft is smaller you could use an insert. If it is larger it could be a problem. I think the part is hardened steel and would be hard to machine.

The shaft end has a 4 mm hole and a set screw. One would have to machine a shaft end to fit.

If you are serious about getting this to work buy one of the U-joints. Send your motor, U-joint, drive washer, etc to Lee machine shop. I would bet Lee can make it all work.

John Rist · « **Reply #62 on:** June 26, 2014, 07:14:53 AM »

Well the bad news is that I trashed the LA-5 again and I will not be attending the NATS. The good news is that the DO-335 is ready for paint. Right now my plans are to attend the the FCM. Hope to bring my Extra 300S (Fun Scale) and the DO-335 for 1/2 A scale. Possibility I may try my hand at beginners stunt.

John Rist · « **Reply #63 on:** August 04, 2014, 12:00:27 PM »

I finally have finished the 3rd generation DO-335. In the photo is the family tree of the 3 generations. The small one was first. It was too small. Second one was bigger but too heavy. It didn't want to fly. It had 3 problems: Too heavy, bad airfoil, and elevator on one side only. This leads us to the 3rd generation. 1: is lighter. 2: It has a real airfoil (S7055) extracted from the book Summary of Low-Speed Airfoil Data by the University of Illinois. 3: It has the elevator on both sides.

The test flight one day this week will tell the tail!

John Rist · « **Reply #64 on:** August 04, 2014, 12:02:14 PM »

More 3rd gen DO-335 photos

Tim Wescott · « **Reply #65 on:** August 04, 2014, 12:44:49 PM »

It looks like there's a lot of hard work and craftsmanship in all three planes. Hopefully the 3^rd time will be a charm!

Allen Goff · « **Reply #66 on:** August 04, 2014, 04:36:00 PM »

John, can't wait to see it fly.......3 weeks away.
Blessings
Allen

RknRusty · « **Reply #67 on:** August 04, 2014, 08:14:09 PM »

John that is some piece of work! I mean that in a great way. I bet the Tee Dee uses more gas. My Norvel .061s sip fuel compared to my Tee Dee .049s. So, which engine do you want to shut down first?
Rusty

John Rist · « **Reply #68 on:** August 04, 2014, 08:42:10 PM »

Quote from: RknRusty on August 04, 2014, 08:14:09 PM

John that is some piece of work! I mean that in a great way. I bet the Tee Dee uses more gas. My Norvel .061s sip fuel compared to my Tee Dee .049s. So, which engine do you want to shut down first?
Rusty

That's the beauty of inline twins. It doesn't matter which one quits first.

John Rist · « **Reply #69 on:** August 28, 2014, 09:11:51 PM »

Well after almost destroying it I finally have it working. The problem was that I couldn't keep the back engine running. To make the long story short I had put a NORVEL AMD 061 on the back. I started out with a balloon tank and then I tried a bladder tank. No matter what I tried it was not a happy camper. I am not sure what the problem is but it appears that the NORVLE AMD does not like reverse air flow over the venture. So as the air blast from the front engine would change the NROVEL would go nuts and quit. You could gets things running OK but on launch the airflow would change and the NORVEL would die. The cure was to put a stock TD with a product engine 049 jug on the back. First test run on the bench and every thing was happy. Fist test flight today both engines ran the full flight (17 laps). By the way the front engine is a TD 051. So Broken Arrow here we come.

PS I may even have my LA-5 back in the air by then.

John Rist · « **Reply #70 on:** September 05, 2014, 04:38:16 PM »

The DO-335 was dissembled, cleaned, paint touch up, new decals and reassembled. After her many crashes (back engine kept quitting) she is ready for her first static judging!

More good news the LA-5 is back together, wings are covered, and tomorrow I start the painting process. It too will be ready for Broken Arrow!

Praying for good weather. Hope to see all of you!

Fred Cronenwett · « **Reply #71 on:** September 05, 2014, 08:09:53 PM »

John,

we are getting ready here for the Broken arrow and will be excited to see the DO-335 in person!

Looking forward to seeing you again

Fred

http://lafayetteesquadrillecl.wordpress.com/lafayette-esquadrille-cl/control-line-contest-st-louis/control-line-stunt-pampa-scale-broken-arrow-st-louis/

RknRusty · « **Reply #72 on:** September 05, 2014, 10:11:11 PM »

Good luck, John!

Rusty

John Rist · « **Reply #73 on:** September 15, 2014, 08:35:23 AM »

Sunday, after Church I test flew the LA-5. It has survived all of my abuse! It still flies great. So it's off to Broken Arrow with 3 airplanes: Extra 300S, LA-5, And the DO-335.

Hope we have good weather!

Will Hinton · « **Reply #74 on:** September 15, 2014, 12:08:31 PM »

Knock'em dead, John!!

Allen Goff · « **Reply #75 on:** September 15, 2014, 02:56:11 PM »

John you realize what you have done here? You have upped the anty on 1/2A scale competition. If someone wants to do well in this event you better do your homework, because John has! Great looking airplane. May we see you at the NASA scale classic in a couple weeks?
Hope all goes well this weekend in St.Louis.
Blessings
Allen

Fred Cronenwett · « **Reply #76 on:** September 24, 2014, 06:03:00 PM »

John flew his DO-335 at the Broken arrow, the video not quite in focus but still shows the model flew very well

Enjoy....great Job John, 2nd place out of 5 entries

Fred Cronenwett

John Rist · « **Reply #77 on:** September 24, 2014, 09:22:47 PM »

Fred,

Thanks!!!!

A great video of the best flight ever on the DO-335. I actually worked at having the front engine quit first. When it dose I can land and taxi on the back engine. When the front engine stops the back engine has little or no cooling so it heats up goes over lean and slows down. Once on the ground it contentious to slow down until it quits. I will claim that I designed it that way - that it wasn't an accident. Anyway however it came about it is now called a feature.

Thanks to all who put on the Broken arrow Scale contest. I had a blast.