Dragonfly or RC Bee control snap ring

Hi David, I have an assortment of "K-D"-brand snap-rings.. but I don't have snap-ring pliers to remove the installed ring on my .049 cylinder. If you can source the "K-D" brand.. it looks like you'd want the #3100-68




The thickness is the same (.040") as the ring on my sleeve and the inner-diameter is 5/8" nom. (.630"). The smaller 3100-62 has a thickness of .035" and its inner-diameter looks too small.

I would try to find one with a 5/8" ID. A good hardware store will stock snap-rings. While you're there; borrow a tape-measure to check them. That should measure close-enough.

Auto Zone sells an 18-piece assortment ("HELP-brand") of sizes between 1/4" and 1" for $3.79

http://www.autozone.com/gaskets-and-miscellaneous-fasteners/snap-ring/help-18-pcs-1-4-to-1-in-external-universal-snap-ring-assortment/720938_0_0

They had them at Lowe's.  It was called a 5/8" external retainer ring.  Thanks.

I think what I have is a Dragonfly with an RC Bee rubber muffler ring.

Added later: No, I think the throttle ring is also RC Bee.

David Ingham wrote:They had them at Lowe's.  It was called a 5/8" external retainer ring.  Thanks.

I think what I have is a Dragonfly with an RC Bee rubber muffler ring.

Added later:  No, I think the throttle ring is also RC Bee.

Did the "Lowes-sourced" 5/8" external snap-ring fit snugly into the groove in your Cox .049 cylinder-sleeve David? This would be useful info for others having a sleeve with a missing snap-ring. Sleeve meaning; an "exhaust-throttle" sleeve.. not a muffler. Engine-cylinders were usually centerless-ground to fit an exhaust-throttle sleeve. Some Cox engines came with them.. but I believe that the cylinder/piston/sleeve was also available "separately".. as a replacement/hop-up part.

It fit quite snugly, so I was a little afraid it was going to break. But my cheap snap ring pliers handled it.
I needed a washer-like spacer under the throttle/muffler ring to hold it up over the ports, I think it is an RC Bee ring on a Dragonfly. The ring turns very smoothly, but I am not sure it is tight enough. The cylinder is specially machined, but I don't know if it is the one that came with the ring. I am thinking of using it with both the throttle and the muffler in a model.

David, throttle ring doesn't have to be tight, if it turns and there is no slop. The oil droplets in the exhaust helps to keep it sealed around the cylinder. Is you cylinder the 2 slit exhaust port type like the Sure Starts? I know what you're asking for, I think some of the non-throttle mufflers came with an extension ring to sit the muffler a touch higher. My .020 Cox muffler has such. I don't know if such is available for .049s.

RC Bee parts diagram doesn't show any such ring.



I mounted my old Ace RC throttle ring on my Cox Centurion .049 given to me by a friend.



It has the Sure Start styled 2 slit exhaust. The throttle ring could use a slight boost to lift it up so the exhaust slits are exposed when throttle ring is in the open position. I believe the ring was designed to work with a cylinder with SPI. With the exhaust port cut lower, then it matches the throttle ring slot. Otherwise, this engine is dysfunctional as is.

I used this Ace RC throttle ring quite extensively back in the late 1970's on my Airtronics Q-Tee, worked well. The RC Bee throttle muffler worked really well, produced a touch more power with silicon muffler baffle removed. I flew my Sterling Minnie Mambo both ways.

Anyway, another possibility may be to use one of Cox International's or Ex-Engines' Tee Dee style SPI cylinder modified from Sure Start cylinders. I'd inquire with them whether your throttle ring would fit over these.

Also, another solution may be to use one of their non-muffled throttle rings instead. If you do, I'd inquire if the will work with a Sure Start 2 slit cylinder or SPI cylinder, depending on what you have.

Thanks Ghostler, I think it will work now. The main question now is whether to use it in a Keith Laumer Pushup or to make a throttle for a Pee Wee to keep the original scale. Pushup doesn't need the clink tank. If I fabricate a throttle ring, it will be valuable to know that it doesn't have to fit tight.
That diagram looks like what I have, except for the later type starter.