Cox Olympic .15

Godsey3.0 Wed Aug 08, 2012 10:02 pm

Hey guys,

I have the opportunity to buy a Cox Olympic .15 in good shape. I only want to get it though if it is a good engine and if I can get it on a plane easily. What problems can I expect with it? Will I have to find a reset tool for it or does it have a wrist pin? I remember that being discussed some time ago. I think someone on here was making them. Can I tune it easily on pressure? If I use a standard plug conversion will I lose much power? What power should I expect with this engine naturally? Also, what plane would be ideal for it? I was thinking maybe the Jr. Satan but did not know how this plane would handle. If it flies as well as the Lil Satan then I am all for it. I think a smaller Combat Wing like the Jr. Satan would be better before I try and maiden this Voodoo I got cut out.

Rolla

Jason_WI Wed Aug 08, 2012 11:11 pm

Here is a video of mine running. Check the amount of piston ball socket slop and make sure the reed is OK. If the slop is excessive and it is reset then you will most likely lose the SPI once it is reset. I made reset tools for the .15 but haven't been down in the basement much to finish the few that I have started.......

Never ran one on a head adapter but being a .15 you may not loose that performance by using one.

**RknRusty** Thu Aug 09, 2012 8:52 am

That's smooth as silk, Jason, Nice engine.
Godsey, the rear venturi might offer some mounting challenges for kits designed for traditional beam mounted engines. I doubt if replacement glow plugs/heads would be a problem.

JPvelo Thu Aug 09, 2012 9:31 am

@Jason: what size prop are you running in the video?

Godsey3.0 Thu Aug 09, 2012 9:38 am

Wow. That was a very nice run. Quite similar to a Space Hopper. I am hoping this engine is not much longer than a Tee Dee. I know a Space Hopper is only a bit longer. I could run it on a balloon with the Jr. Satan. It shows a Veco Tank. If I can tune it easily with a pressure system then I will most likely squeeze in a bladder.

Jason: Sending you a PM

Rolla

JPvelo Thu Aug 09, 2012 11:22 am

The Venturi puts the engine out the same distance as if it had a propprtionatly sized babe bee tank, if that makes sense. Will post a picture of a sportsman .15 laid over a junior Satan plan later if that helps.

Godsey3.0 Thu Aug 09, 2012 12:28 pm

Are the Olympic and Sportsman essentially the same? Besides bearings and anodizing. I am also capable of getting a Tee Dee .020 for $10 more. My mother told me to decide on a Birthday Present and that may be it. He only wants $55 for the Olympic.

Rolla

**RknRusty** Thu Aug 09, 2012 1:59 pm

Godsey3.0 wrote:Are the Olympic and Sportsman essentially the same? Besides bearings and anodizing.
Rolla

The Olympic is referred to by mh-aerotools.de as "the Sportsman's stronger brother."

Godsey3.0 Thu Aug 09, 2012 4:02 pm

So I guess the Olympic is to Tee Dee as Sportsman is to Medallion? If that statement made much sense. That is how one would look at it in Geometry.

Rolla

JPvelo Thu Aug 09, 2012 6:16 pm

Sportsman laid out on Jr. Satan plan.
https://i.imgur.com/twWPn.jpg
https://i.imgur.com/zQr7J.jpg
This is the next build in my que.
I don't know if you can use the commercially available conversion heads on the Olympic.
They are made for a medallion/td cylinder which is slightly larger than the sportsman/Olympic cylinder. The cylinders are not interchangeable between engines so I'm not sure if they are the same size glo plug.

Jim

**RknRusty** Thu Aug 09, 2012 6:19 pm

Godsey3.0 wrote:So I guess the Olympic is to Tee Dee as Sportsman is to Medallion? If that statement made much sense. That is how one would look at it in Geometry.

Rolla

I don't know about that, but I can say what a Medallion is to a Tee Dee. A Medallion is a rotary version meant for fun fliers that don't want to fuss with pressure and an easy to clog shower head and the complex porting of a Tee Dee.

A simple carb and single port, non-SPI cylinder makes it an engine you can take it to the field, fuel up, flip the prop and reliably be flying at peak performance. Not nearly as finicky, but at the trade-off of lower power and speed. Still faster than the reedies, maybe, and much less troublesome. I put a new SPI set on mine and it's still a very friendly engine, and faster than with the old #2 single port setup. Runs great on suction.

Godsey3.0 Thu Aug 09, 2012 6:30 pm

Sorry. I worded that wrong. I meant the Olympic is to Sportsman as the Tee Dee is to Medallion. The Olympic being the more powerful, costly version.

Godsey3.0 Thu Aug 09, 2012 6:31 pm

I guess one could recess the venturi into the Leading Edge. Probably also have to extend the engine bearers. Has anyone flown this plane?

Rolla

Edit: How far could one safely cut into the leading edge? I would have a balsa block in between the two center ribs for the engine bearers to attach to. Would this supply enough support to drill all the way through the Leading Edge?

**RknRusty** Thu Aug 09, 2012 8:06 pm

Keep in mind, the farther forward the prop is from the CG, the less aerobatic the plane will be. Extending the nose might turn it into a nice stable trainer instead.

JPvelo Thu Aug 09, 2012 8:23 pm

I would think with the engine moved forward it would have the proportions of a scaled up little Satan, taking the .049's tank into consideration? Where does your little Satan balance Rusty?

**RknRusty** Thu Aug 09, 2012 8:31 pm

JPvelo wrote:I would think with the engine moved forward it would have the proportions of a scaled up little Satan, taking the .049's tank into consideration? Where does your little Satan balance Rusty?

If I recall correctly, 7/8" behind the LE.

**Cribbs74** Thu Aug 09, 2012 9:30 pm

Godsey3.0 wrote:I guess one could recess the venturi into the Leading Edge. Probably also have to extend the engine bearers. Has anyone flown this plane?

Rolla

Edit: How far could one safely cut into the leading edge? I would have a balsa block in between the two center ribs for the engine bearers to attach to. Would this supply enough support to drill all the way through the Leading Edge?

I bet Ken Cook has flown one.

The good thing is the plywood skid already cuts the leading edge in two so if you take into account the engine bearers and nacelle it provides plenty of beef around the leading edge. Personally I would just move the engine forward and negate the issue.

Ron

JPvelo Tue Aug 14, 2012 2:44 pm

http://www.ebay.com/itm/170892962216?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649#ht_500wt_922

zeissman Tue Jun 04, 2013 2:11 pm

JPvelo wrote:Sportsman laid out on Jr. Satan plan.

This is the next build in my que.
I don't know if you can use the commercially available conversion heads on the Olympic.
They are made for a medallion/td cylinder which is slightly larger than the sportsman/Olympic cylinder. The cylinders are not interchangeable between engines so I'm not sure if they are the same size glo plug.

Jim

In response to your supposition Jim, the first version of the TD.15 uses the EXACT SAME CYLINDER as the Olympic. This is the thin walled cylinder with 2 exhaust ports, 2 bypass flutes and dual boost passages cut into each flute. Moreover, the thin walled cylinder for the Medallion is the EXACT SAME CYLINDER as the one on the Sportsman.

While it is true that the .15 TDs & Medallions were changed due to the problems caused by the thin walled cylinder, the later cylinders still use the same size glow heads. Thus, any replacement glow head designed to fit a .15 TD or Medallion will also fit an Olympic and a Sportsman. IOW, while the thicker cylinders are not interchangeable with the thin walled cylinders, the glow heads are interchangeable.

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