Backplate for a Cox RR-1

defhill3 on Thu May 12, 2016 7:35 pm

I need a backplate for a RR-1. I suspect that it is very rare.

Can you modify a normal Cox Backplate to fit an RR-1?

Thanks in advance!

pkrankow on Thu May 12, 2016 8:50 pm

https://www.youtube.com/watch?v=u9lzUjfWIj8

looks like a stunt tank back to me... I wish I had one to know for sure
Phil

defhill3 on Thu May 12, 2016 9:39 pm

Back in the middle 1950's A couple of us were flying down at the McKinley grade schoolyard in Ponca City Oklahoma. I was flying a Sterling F-51 profile with a K&B .32 for power on 60 foot lines.

A kid walked up with a built Goldberg Swordsman 18 with a RR-1 for power. He didn't have a handle or lines and he wanted us to fly it for him. We told him we only had 60 foot lines, but we would try to fly it on them. I think he had a can of Cox fuel. We hooked the airplane up, started the engine, and my buddy launched it for me. The Swordsman 18 flew, but just barely. If I tried to get over 4 feet high, the lines would sag down and the Swordsman 18 would start coming in the circle. If I flew lower, the plane would stay out on the lines. The engine finally ran out of fuel, and I landed it.

If you don't believe this, I don't blame you.

About a year ago, in a box full of stuff, I found the complete front end of an RR-1 that looked brand new. I have been looking for a tank and backplate for a year, and just won a tank and rotor off of ebay. Now, all I need are 4 through bolts and an RR-1 backplate.

If can get this engine completed, I may buy a Swordsman 18 and try to fly it with the RR-1!

**WingingIt74** on Thu May 12, 2016 9:47 pm

You'll have to modify the backplate quite a bit to work. The one I have, they modified the tank and backplate, which makes the tank not worth much.

**RknRusty** on Thu May 12, 2016 9:52 pm

I hope you get it running. You may be surprised at the power of the RR1. With the right prop, pretty close to a Tee Dee. A 5.5 or 5.25x3 Master Airscrew will work well on it. I don't know what size APC, but they give you a lot of choices. I'd be curious to see how one of their 5.25x4s works.
Rusty

**WingingIt74** on Thu May 12, 2016 9:55 pm

I still have that RR-051, I have yet to run it. That's the one with the modified tank/backplate.

https://www.coxengineforum.com/t7677p20-my-second-rr-1-aka-rr-051

kevbo on Mon May 16, 2016 11:34 am

RknRusty wrote:I hope you get it running. You may be surprised at the power of the RR1. With the right prop, pretty close to a Tee Dee. A 5.5 or 5.25x3 Master Airscrew will work well on it. I don't know what size APC, but they give you a lot of choices. I'd be curious to see how one of their 5.25x4s works.
Rusty

Be sure to also try some props that will let the engine rev-up as well. Like a 5x3 or even a little less.

This is a point I never got in my younger days. I'd stick a 6x3 or even a 6x4 on a Tee-Dee, figuring a hot engine like that should handle more prop than my lame old reedies. Wrong!

The freer breathing engines don't make much if any more torque at modest rpm. (13-14K) In fact they can be worse...the small venturi gives reliable mixture, and the single bypass can have scavenging advantages.

The mild reed engines start losing torque due to breathing restrictions somewhere around 12-14K rpm, putting peak power around 14K rpm usually. The hotter engines will keep breathing, (and making good torque) on up to 18 or even over 20K, which lets them make proportionally more power. But to get there, they need a prop that lets them wind up.

defhill3 on Mon May 16, 2016 7:10 pm

I found out that the 1956-57 RR-1's did not have vent tubes in the backplate. there wasn't a screen in the intake, either. Some later models of the RR-1 used backplates with vent tubes that were blocked.

I am going to modify a normal Cox backplate with vents and assemble my RR-1.

If I ever find a correct RR-1 backplate, I'll install it.

The only thing harder to find than an RR-1 is an Ignition Orwick .29. I could use one of those.

defhill3 on Mon May 16, 2016 7:26 pm

I just noticed that some Golden Bees have backplates that don't have vent tubes. I have several of those, so I'll modify one of them, and install it on my RR-1.

defhill3 on Tue May 17, 2016 4:24 pm

I got my RR-1 together; it looks stock. The RR-1 venturi tube is longer than a gold bee venturi tube. That's why I had to use a 3/16" drill and drill all the way thru the gold bee backplate. The RR-1 venturi tube extends all the way to the back of the backplate when the engine is assembled. It takes 3 hands and an extensive vocabulary to assemble an RR-1, but I finally got it done.

I had several sizes of fuel tubing, and it took many tries and several tubing size changes to get the small packing made to fit the slot at the rear of the RR-1 venturi tube.

**Cribbs74** on Tue May 17, 2016 9:13 pm

Good job De!

I have a NIB Goldberg Swordsman 18 if you are interested.

Ron

defhill3 on Tue May 17, 2016 9:53 pm

Thanks Ron,

I'll get back in touch with you this weekend.

De

Sounds good!

Mark Boesen on Tue May 17, 2016 11:33 pm

The first couple years the RR-1 backplate had tubes not drilled out, with the intro of the Golden Bee, Cox discontinued the vented backplate. As a rule the first backplates were a clear plating, followed by a yellowish color, then finally a brass color, however that wasn't always the case, i've seen early backplates with only one hole drllled, and clear plated non vented backplates and yellow plated non drilled vent tube backplates...

defhill3 on Fri May 20, 2016 4:48 pm

Thanks for the correction Mark,

It seems that I had everything backwards.

Mark Boesen on Sat May 21, 2016 12:06 am

Here's a photo of 'Mudhens' RR-1, the very first version had no grooves on tank.

KariFS on Sat May 21, 2016 12:56 am

Mark Boesen wrote:Here's a photo of 'Mudhens' RR-1, the very first version had no grooves on tank.

Nor on the crankcase neck?

Mark Boesen on Sat May 21, 2016 10:50 pm

Yes, the initial issue (appx. 6 months or less) had a smooth blue tank with smooth aluminum crankcase. 2nd version had ribbed blue tank with aluminum ribbed crankcase and 3rd, ribbed blue tank with gold anodize ribbed crankcase. The variations to the types included clear or gold anodize tank backs, with or without capped fuel filler tubes. Spinner changed to Tee Dee type, with introduction of Tee Dee.

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