WTT TD .049 parts for Medallion .049 parts

No worries Rusty, my intent is to have TD performance while still retaining the hard tank.

It may work it may not and I am sure performance will be hindered somewhat. I still find bladders somewhat fiddley and I hate when they burst. The one way valve you use sure makes it a whole lot easier though.

It's just something I want to try, doesn't look like anyone wants to give the Medallion assemblies up.

Cribbs74 wrote:No worries Rusty, my intent is to have TD performance while still retaining the hard tank.

It may work it may not and I am sure performance will be hindered somewhat. I still find bladders somewhat fiddley and I hate when they burst. The one way valve you use sure makes it a whole lot easier though.

It's just something I want to try, doesn't look like anyone wants to give the Medallion assemblies up.

it swap my 15 madillion venturi bits for 15 td venturi bits

Sorry, looking for .049 bits. I probably should have mentioned that.

oh sorry
please could we do it any way? it will turn out the same wouldn't it?

Sorry, I am only wanting to convert a couple of .049 Medallions.

Ron, the Medallion carb bodies are still available. You could easily press out any horseshoe backplate spraybar and retrofit it to the Medallion body. This can be done with the standard 80 TPI needle or the 128 TPI. Tank design is mostly responsible for the fuel draw issues of a TD. One would think that trying to get a speed plane to go in circles should be very simple vs a stunter. Well I found this to be totally opposite. I could never get my TD's to function on a hard tank on a speed model. This was mainly due to the wedge tanks which place the pickup too far outboard. Moving the tank closer to the engine's centerline is a must. I've seen a few TD's perform well using the Medallion body. However, it's still going to run like a TD. If your looking for a more timid run, changing the crank and also the cylinder is needed. If fuel draw is your only issue with the TD, I would take a few venturi's and choke them down. I've seen this done very successfully using JB weld and then the center was drilled to the desired hole. Ken

so Ken , pretty much the crank with the larger / longated hole for more fuel on the TD causes the fuel draw problems? Stuff , I need to reread the post as to what Ron is wanting to accomplish // better fuel draw with the same power?

Eric, the TD has a large venturi. It really is borderline to run on suction. Yes, it will work, but you have to meet certain requirements to do so. Now you can run it on a bench all day long with any tank, the problem begins when you install it on the plane. A tank that's centralized directly behind the engine as in a full bodied plane runs the best compared to a profile with it's tank mounted outboard. Certain factors can improve the reliability of a TD such as a Uniflow tank. Most here run standard vent and this can also be improved upon by capping one of the vents during your run.

As far as power is concerened, the TD should run with a little less power due to the choke area being smaller hence the fact that it allows it to draw fuel better. The Medallion has it's spraybar running through the carb body. The TD is a sprinkler with no spraybar running through the venturi.

The solution to running a properly designed tank on a TD is having a tank long and thin. This is almost impossible to do with most of the models we see available without making modifications to the fuselage. The pickup of the tank shouldn't be any further outboard of the fuel barb of the TD spraybar. Most people choose the Perfect wedge tank. This has the fuel far too outboard which automatically places the engine in a lean running condition when the head pressure of the tank drops off. This means starting off very very rich and then when the fuel load disperses the engine will come on. Making a uniflow setup can assist in the engine run.

If your flying a wing for instance, you will find that quick maneuvers pin the fuel in areas inside the tank which makes the engine either quit or nearly quit. Putting the Medallion body on the TD in this regard will help solve a lot of those headaches due to an increase of fuel draw. The crank is pretty much irrelevant here I was just stating the differences.

Cribbs74 wrote:Sorry, I am only wanting to convert a couple  of .049 Medallions.

Ron: I thought I had mentioned to you before that I had purchased 10 of the Medallion .049 red plastic venturis on ebay last year. Cheaper by the dozen. I am ordering a couple of the spray bars from ESP and will pay in a couple of days, so that only leaves the needle assembly. Looks like someone needs to look into the suggestion of using a needle/spraybar assy. from the postage stamp mount or the horseshoe mount and see how they fit. Since I have a couple of cracked venturis it looks like it's me for now. Shoot me a PM with your input.

Happydad   I'm retired          

Ken Cook wrote:              Ron, the Medallion carb bodies are still available. You could easily press out any horseshoe backplate spraybar and retrofit it to the Medallion body. This can be done with the standard 80 TPI needle or the 128 TPI. Tank design is mostly responsible for the fuel draw issues of a TD. One would think that trying to get a speed plane to go in circles should be very simple vs a stunter. Well I found this to be totally opposite. I could never get my TD's to function on a hard tank on a speed model. This was mainly due to the wedge tanks which place the pickup too far outboard. Moving the tank closer to the engine's centerline is a must.  I've seen a few TD's perform well using the Medallion body. However, it's still going to run like a TD. If your looking for a more timid run, changing the crank and also the cylinder is needed. If fuel draw is your only issue with the TD, I would take a few venturi's and choke them down. I've seen this done very successfully using JB weld and then the center was drilled to the desired hole. Ken

Ken: The Medallion spray bar hole is very large. about 1/8inch as a guess, and the horseshoe and postage stamp spray bar assemblies are only about 3/32inch as a guess. I haven't  had a chance to press out the spraybar from either one of those yet due to my limited ability at the present, but eyeballing it tells me the Medallion spray bar is a little larger. I was able to take a picture of the two side by side and I will enclose here. I haven't measured the two yet because I haven't disassembled my Medallion or pressed out either one of the other 2 mentioned. I have contacted ESP at his ebay site and reserved a couple of the spray bar assemblies, but that still leaves us without a needle assembly. I will also enclose a picture of several needles. From the right: babe bee, TD, Medallion, bent Medallion, Medallion?. Enjoy.



horseshoe back plate next to Medallion venturi



Misc.  Cox needles  medallion?, Medallion bent, Medallion, TD, babe bee.

happydad   I'm retired              

Thanks HD,

Just let me know when you get everything squared away. I'd be happy to grab a couple. Thank you for helping me out!

Ron

ALL: BTW I have TD parts minus the crankcase.

1 - TD crankshaft
1 = TD venturi, needle, spraybar assy. (available as a set only)
1 - crankcase end cap
1 -    collet piece that holds venturi on front of crankcase, (forgot name)
1 - TD .049 cylinder/piston set

edited 6:20p.m. 8-22-15 = to correct list of parts
sorry I was unable to find the TD venture today. I may have traded it when I traded the TD/Medallion crankcase, (yes the .049 crankcase is used for both the TD .049 and Medallion .049 engines).
 Sorry for the mistake.      

HD  I'm retired              

Well this should settle the issue of whether or not a Cox horse shoe spray bar will fit a Cox Medallion venturi.



As you can see from the picture the venturi measures 0.150 inch across the flat part of the venture spray bar opening, where the spray bar is round and measures 0.118 inch across the round part of the knurled portion of the spray bar, same on both ends.


happydad    I'm retired                

VGE had these listed with an incorrect title but the photo and description were right. Maybe he has more

happydad wrote:
I have contacted ESP at his ebay site and reserved a couple of the spray bar assemblies, but that still leaves us without a needle assembly.

I have used the needle from a product backplate in a Medallion .049.  The needle profile is slightly different, but it does work.  Maybe not optimally, but I guess you could play with the needle profile using some sandpaper and see what you get.

On another tack, if you have extra medallion bodies, you could take a spray bar from a product engine, or preferably a fine needle spray bar from a postage stamp backplate, and JB Weld it in the Medallion body. I think I'd go for the product needle, though.

The Substitution Mark

crankbndr wrote:VGE had these listed with an incorrect title but the photo and description were right. Maybe he has more

Thanks for the info.  A little on the expensive side. Bernie offered 3 other alternates which I will check out. Since the spray bars are currently available I would prefer to use a needle that fits instead of JB welding a smaller spray bar and using a different needle.
   Checking out the alternatives.

Happydad.  I'm retired.          

The spraybar will fit. It's not a direct replacement but a solution. Bush the spraybar to  make it fit or JB weld it in. Not pretty but it will work. I make bushings either from brass or aluminum which is directly available from K&S. When I find time I can get a little lathe time and make whatever I need as I do this for Norvel's and other engines.

After purchasing several Medallion .049 spray bars and needles I have assembled 4 assemblies.

for some reason this MacBook cannot "host" a picture or the picture is too large, 2.6MB.
I will edit this post in a few minutes from a PC after I transfer a bunch of pictures from this MacBook the the PC.

sorry  happydad

edit 5:46p.m. 8-28-2015 - to hopefully add pictures from a PC

same issue. maybe later
8-29-15 3:23p.m.


Venturi assembly


Parts of Venturi assembly

It is easy to upload pics when it works.  HD

happydad  I'm still retired                

I wonder if a Tee Dee assembly would draw fuel better if you filled the gutter around the base of the venturi with JB Weld, plugging two of the sprinkler holes, then enlarging the remaining hole to a little larger than the spray hole of the needle assembly. Line the two holes up when you tighten the venturi... may require some sanding of the boss on the carb body to get them to align when it tightens. And for the same reason, leave a little of the gutter on each side of the venturi inlet.

This would keep it from drawing mostly from one hole, while cavitating around the others.
Just pondering, I've never heard of it being done or suggested.
Wow, did I actually think up a good idea that the top engine guys haven't tried?
Rusty

RknRusty wrote:I wonder if a Tee Dee assembly would draw fuel better if you filled the gutter around the base of the venturi with JB Weld, plugging two of the sprinkler holes, then enlarging the remaining hole to a little larger than the spray hole of the needle assembly. Line the two holes up when you tighten the venturi... may require some sanding of the boss on the carb body to get them to align when it tightens. And for the same reason, leave a little of the gutter on each side of the venturi inlet.

This would keep it from drawing mostly from one hole, while cavitating around the others.
Just pondering, I've never heard of it being done or suggested.
Wow, did I actually think up a good idea that the top engine guys haven't tried?
Rusty

Rusty: I have received all the parts from Matt our Cox parts good guy, (+10), and have put together 3 Medallion .049 venturi-spray bar-needle assemblies. and took a picture of the assembly and the parts that make up the assembly. Sometime today, Saturday I will figure out how to post pictures using the postimage.com system and add to this thread those pictures. I'm not sure if I will sell the assemblies on ebay or offer them to CEF members first. Ron Cribbs and I sort of kicked around the idea for a while so I am waiting for his comments before I proceed. The only difference is the needle used is not the original Medallion .049 needle since the only 1 I have found is selling for $16.00 plus shipping, (approx.), and I am using a needle that Bernie suggested. It is the long brass needle from the product engines. I felt the long needle could always be shortened if users felt it was too long, but not visa-versa.

happydad  I'm just plain hot and old tired   102degrees today here      

happydad

http://m.ebay.com/itm/Cox-049-09-Medallion-Airplane-Engine-Spraybar-049-09-/281774965635?nav=SEARCH

JPvelo wrote:http://m.ebay.com/itm/Cox-049-09-Medallion-Airplane-Engine-Spraybar-049-09-/281774965635?nav=SEARCH

There ya go. Get 'em while the gettn's good.

RknRusty wrote:

JPvelo wrote:http://m.ebay.com/itm/Cox-049-09-Medallion-Airplane-Engine-Spraybar-049-09-/281774965635?nav=SEARCH

There ya go. Get 'em while the gettn's good.

it is true the availability of the spray bar is becoming limited. I just purchased 4 from ESP and I am not sure how many he and coxengines.ca have left. Maybe Bernie will find a stash in his new find. The parts in question are the Medallion venturi and the needle. Bernie has suggested using the product engine short or long brass needle and they seem to work fine. I have a few of the red plastic .049 venture I purchased about 2 years ago.


venturi-spray bar-needle assembly


parts of assembly

   See other comments on availability above.

happydad  I'm still retired     still confused about Cox twin engines??  but having fun