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Antiques or Out of Business > Dubro 505 pitch blades help

sherpa
New Heliman
Location: Madrid 28002-Spain

Hi friends .My name is Jesus from Spain ,and this is the fisrt time in your forum.I have an old time helicopter colletions on flight ,one Huey Cobra and Miniboy from Shulter,one Bell 212 from Graupner , one Jet Ranger and Alouette from Kavan and a 505 from Du-Bro. I have many kits reviews about the Du-Bro 505 Wirlybird model like RC Modeller,MAN,Modellistica,Popular Mechanic and others but none have been able to obtain the pitch blade degrees.I have tried to flight it sometimes but has been impossible to do it. (I have tried 4º on the main blades but I´m afraid this set is not ok) .The kit had a wood template (pitch gauge) to use on the pitch blade set, but probably mine was loosen a few years agó..If you know a person that have a Du-Bro 505 or have notice about that , I will be very gratefull if can help to me about the main blades pitch degreés.I have just seen the Youtube video about the 505 and I would like to put my Du-Bro on flight Thanks in advance Jesus

02-13-2008 10:03 PM

HFr
Senior Heliman
Location: Lagrange ,in USA

Welcome to the board ... I think the pitch degree for the 505 is 6 degrees and I think one of the guys on here said he has his at 7

02-14-2008 12:52 AM

sherpa
New Heliman
Location: Madrid 28002-Spain

HFr thanks for your help.Somebody told me 4º.With this set ,the speed rotor is low and dificult to flight. I don´t know if 6º will be better.The ideal thing would be to find someone who has one and measure template.

02-14-2008 09:17 AM

HFr
Senior Heliman
Location: Lagrange ,in USA

Sherpa
I do have one ,with a manual and I measured the 6 degrees off the guage .The book don't give the degrees in writing ...just says put together the gauge on a flat surface and use it

The main rotor really don't do the main lift on this bird ... it really slows it down so you can turn a higher rpm on the airplane prop which is really what you use to lift off with ... all the big rotor does is to control direction of flight ... got to remember this is the first helicopter and they didn't have it all figured out yet .
This other guy said don't even airfoil or round the front of the blades as you want that rotor to drag so you get a higher RPM on the airplane prop.

I saw the proto type of this helicopter at Greenville ,Ohio funfly back in 78 or so and all Dave Gray did was pull out an alum fuel tank with a K&B motor /prop attached to it and two red shop rags to the bottom of the fuel tank ... they started the motor and threw it into the air and it drifted for a few moments across the feild ,,,just free flight and then ran out of gas and crashed to the ground ..... don't need big blades to hover (look at the airplane guys now )
Hopefully heli//headcase will chime in here pretty soon as I think he was the one that told me this .

02-14-2008 11:22 AM

heli_headcase
Veteran
Location: Hovering around Atlanta

Why doesn't someone ask me? :D

Hi Sherpa,

That 505 on youtube.com is my heli. I made a custom pitch guage jig using a Miniature Aircraft pitch guage and dropped the pitch to +2 degrees per blade.

My reasoning is this: In the 1970's, when the Whirlybird was designed and sold, .40 c.i. (6.5cc) engines were not as powerful as the ones made in the last 20 years and I was going with an engine with more power. Since the newer engine will provide more lift from the prop, less lift would be needed from the main blades AND because a faster spinning rotor system should provide a better control feel, lowering the pitch from approximately 5 degrees to 2 degrees should do the trick. I installed a "Tower 40" engine, a sport model engine copied from the very popular OS 40FP, in place of the K&B 40 that I originally expected to use. The Schnurle ported Tower engine would produce plenty of reserve lift off the 10-6 propeller to allow for the drop in lift intended off the main rotor blades.

As anyone can see by viewing the video linked here:

http://runryder.com/helicopter/t390072p1/

...the heli flys perfectly OK. I'll post a few pictures of my modified pitch guage in a few minutes. Need to edit the pictures before adding them to this thread.

HHC

So many heli's - too little time...

02-14-2008 05:26 PM

heli_headcase
Veteran
Location: Hovering around Atlanta

Pitch guage Pix

HHC

So many heli's - too little time...

02-14-2008 05:37 PM

HFr
Senior Heliman
Location: Lagrange ,in USA

Boy ,,was I way off ...that'll teach me to rely on my old memory ...instead of waiting till I go home to read the paper that I printed out from Heli headcase

02-14-2008 07:47 PM

heli_headcase
Veteran
Location: Hovering around Atlanta

Original post edited...

I reread my posting and made a few minor corrections. Some were spelling, some were to improve clarity of the subject. Just so you know...

How many 505s will be operational at IRCHA 2008? Let's "git em done!"

HHC

So many heli's - too little time...

02-14-2008 08:06 PM

Four Stroker
Veteran
Location: Atlanta

Ah ha, so that's why yours actually flys ! Let it spin up so that you can control it. Did you try a 11x5 or 11x6 prop ? 30% fuel ?

02-14-2008 08:18 PM

heli_headcase
Veteran
Location: Hovering around Atlanta

Mine flys because....I donno!

Definitly using 30% because that's what I have. Bad fuel choice because flight times are artificially shortened (higher fuel consumption) and the nitro is hard on the plastic canopy. I guess that besides the boost in power, low throttle reliability is improved, which is a good thing since this engine was NEVER designed to operate without either a muffler or exhaust baffle. Harder to keep the plug hot with an open exhaust port.

I think a larger prop wouldn't suit the RPM range of the engine. More torque should be available to spin the main rotor in theory but only if the engine's torque/HP curve is flat enough to hold the torque high at the lower developed RPM. Remember, this is a two-stroke, not a four-stroke

HHC

So many heli's - too little time...

02-14-2008 08:30 PM

HFr
Senior Heliman
Location: Lagrange ,in USA

Heli headcase ---to hear you talk about fuel and canopy fatigue , flight times etc. and I remember the yuk of old K&B 500 caster too ...hummmmmm...
wonder if I could electrify one and not get run out of the community ?????
Now putting on my flame proof suit and helmet

02-14-2008 09:22 PM

Four Stroker
Veteran
Location: Atlanta

Hey, put an exhaust baffle on it. You even have muffler holes to mount it. People won't be able to hear their turbines running when you fly that thing!

02-14-2008 09:43 PM

heli_headcase
Veteran
Location: Hovering around Atlanta

E-505...wonder if I could electrify one and not get run out of the community ?????

Go ahead, I DARE YOU! I DOUBLE DARE YOU!!!!

A friend suggested going electric on this machine and I gave him the job of engineering the system. No solution was finalized. That's OK with me because I love the noise!

I want people to hear this thing. It's something that will play repeatedly in their heads after the day's events are over.

Hey, I'll still be able to hear my turbine fly because I can't fly my 505 at the same time as the turbine! Hahahahaha!!!!!

About adding the baffle to the Tower 40: There's no practical way to incorporate it. Muffler mounting holes aren't a direct path to add the typical butterfly used with engines of the '60's and early '70's. It works as-is and there's nothing to be gained by adding it. Fly a 505 of your own and do as you want with it. I'm leaving mine alone (except the one in the video is now retired and will be replaced by one is less 'pretty' condition. A true "Beater" )

HHC

So many heli's - too little time...

02-14-2008 10:06 PM

sherpa
New Heliman
Location: Madrid 28002-Spain

Du-Bro 505

Heli_Headcase.Thanks so much for answering my question.I´ll try again with a new .40 FSR type engine and 2º on teh main blades.Now I have another question about the weight.Your 505 copter weighs 3lb 8oz as the manual says ,or is diferent ? I think is very important for control or stability .It is not true?Thanks again Jesus

02-15-2008 05:21 PM

heli_headcase
Veteran
Location: Hovering around Atlanta

Wait! Here's my Weight!

1660g or 5lb 10.55oz

If your engine can lift the higher weight this will force the head speed to be higher. Controllability will be better. At this weight there's no problem with lift. Altitude control is crisp, almost as good as having collective pitch.

Your engine choice is fine but be absolutely certain the throttle arm moves with NO resistance. Remember, there's only a small spring used to pull the throttle rod down through the center of the main shaft. If the rod sticks there's a very high chance the bottom end of the rod can pull out of the throttle bellcrank's push bearing. If that happens, well, you be the judge.

My K&B 40 wasn't suitable for flying on my 505 because the Perry carburettor couldn't be made to move without drag. The Tower 40 carb was as simple and easy to operate as physically possible. The choice was easy.

Good luck!

HHC

So many heli's - too little time...

02-15-2008 08:16 PM

sherpa
New Heliman
Location: Madrid 28002-Spain

Du-Bro 505

Thanks a lot! I see behind the Du-Bro pix that you are restoring a Schluter Huey Cobra.If you need something about the Huey ,I have the original plan and instructions book.I send you a picture of the curious difference between the Schulter and Hirobo mechanic box.Jesus

02-15-2008 09:08 PM

heli_headcase
Veteran
Location: Hovering around Atlanta

He's got a sharp eye...

Quote
Thanks a lot! I see behind the Du-Bro pix that you are restoring a Schluter Huey Cobra.

You're very good and slightly off the mark. That's a Hegi Cobra (I make a big distinction between it and a true Schluter) and I'll try to put it into flying condition for the IRCHA 2008 event this August. The fuse is a total mess, the friend that owned it prior to me attempted to strip the thick layer of paint using chemical stripper and the fiberglass skin suffered greatly. But it has no other real value and for a heli I'm expecting to "waste" trying to fly it, it's the best choice of the Hegis I own.

Thanks for the offer of help though.

HHC

So many heli's - too little time...

02-16-2008 08:03 AM

sherpa
New Heliman
Location: Madrid 28002-Spain

du-bro

Heli_Headcase, the Schnurle ported Tower engine .40 that you use on your Du-Bro is an ABC type with plain bearing or ball bearing?.I have an OS-.40 FP but I think this model is Schnurle but not ABC.Do you think will be OK for my Du-Bro.Thanks

02-16-2008 12:36 PM

heli_headcase
Veteran
Location: Hovering around Atlanta

Perfectly OK.

Quote
the Schnurle ported Tower engine .40 that you use on your Du-Bro is an ABC type with plain bearing or ball bearing?

Plain bearing.

Quote
I have an OS-.40 FP but I think this model is Schnurle but not ABC.Do you think will be OK for my Du-Bro.

It's perfect as long as there's nothing damaged or worn out. The Tower 40 is a copy of the 40FP and neither one is true 'ABC' construction. They're 'ABN', Aluminum, Brass, Nickel. There is one modification you'll have to make to the heli for the FP to fit correctly - enlarge or shift outward the four holes in the engine mounting plate.

With 30% fuel my flight time to 'tank empty' was 6m, 45s. The timer on my transmitter is set at 6 min. Flying until you hit fuel starvation isn't a very good idea with this heli! It falls like a rock!

HHC

So many heli's - too little time...

02-16-2008 04:00 PM

sherpa
New Heliman
Location: Madrid 28002-Spain

Dubro 505 weight

Heli-headcase,following your advice, I have just finished my Dubro with a new OS 40- FP and 2º on the main blades.The last question I have is the final weight.You say to me ,your copter weight is 5 pounds and 10.55 oz (1660 grm) . I have converted 5 lbs 10.55 onz and I have obtained 2560 grm ?. I think this is right ¡My copter weigh 3 lb 15 onz (1763 grm) so I need to add a lot of weight ¡¡¡¡¡
Please tell me if all is OK.Thanks again for your help
Sherpa

03-12-2008 11:45 PM

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