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by rsv1cox Tue Nov 19, 2024 6:35 pm
Cox Engine of The Month
This thing is great!!
Page 1 of 1
This thing is great!!
I'd seen pictures of the throttled Medallion .049 like in the Reviews thread, but I'd never seen one in person. So when one came up on eBay last month I went ahead and got it. Man was that thing ugly. It was dirt covered and frozen up, but after an evening of work it was flipping over nice and easy. I thought about polishing it up, but didn't want to pull the polishing stuff out until I was sure it was a runner. I also added a spring starter that I got from Bernie.
Yesterday I set it up on the test stand with a 6x3 prop and fired her up. AWESOME!!! I couldn't find my tach to check the prop speeds, but the Review section article says it throttles down to 1700 RPM and I believe it. And it was a reliable idle, too. I closed the throttle off all the way and let it idle for a whole minute, and it came smoothly back up to full RPM. When I get my tach, I'll see what the Full and Idle RPM's are, and swap out for a 5x3 prop and see what that throttles to. Too bad these aren't for sale anymore. If another throttle assembly comes up on eBay again, I'm gonna get it for my other Medallion .049. Blows the Ace throttle sleeve out of the water. I have the Sure Start R/C throttle on order from Bernie so I can compare idle RPM's, but that's really an apples to oranges comparison. I have to finish up that Q-Tee I started 20 years ago so I can put this Medallion on it.
The Disputed Mark
Yesterday I set it up on the test stand with a 6x3 prop and fired her up. AWESOME!!! I couldn't find my tach to check the prop speeds, but the Review section article says it throttles down to 1700 RPM and I believe it. And it was a reliable idle, too. I closed the throttle off all the way and let it idle for a whole minute, and it came smoothly back up to full RPM. When I get my tach, I'll see what the Full and Idle RPM's are, and swap out for a 5x3 prop and see what that throttles to. Too bad these aren't for sale anymore. If another throttle assembly comes up on eBay again, I'm gonna get it for my other Medallion .049. Blows the Ace throttle sleeve out of the water. I have the Sure Start R/C throttle on order from Bernie so I can compare idle RPM's, but that's really an apples to oranges comparison. I have to finish up that Q-Tee I started 20 years ago so I can put this Medallion on it.
The Disputed Mark
batjac- Diamond Member
-
Posts : 2375
Join date : 2013-05-22
Age : 61
Location : Broken Arrow, OK, USA
Re: This thing is great!!
Wow, that cleaned up really nicely.
_________________
Don't Panic!
...and never Ever think about how good you are at something...
while you're doing it!
My Hot Rock & Blues Playlist
...and never Ever think about how good you are at something...
while you're doing it!
My Hot Rock & Blues Playlist
RknRusty- Rest In Peace
- Posts : 10869
Join date : 2011-08-10
Age : 68
Location : South Carolina, USA
Re: This thing is great!!
nice,ive never seen one of those
bullit132- Gold Member
- Posts : 197
Join date : 2013-04-11
Age : 63
Location : charleston,sc
Re: This thing is great!!
They used to sell conversion kits with everything needed, i.e. muffler and spray bar etc, both for the .049 and .09. Would be nice to see these conversion kits back in production. Here is an .09 that I've "converted";
Surfer_kris- Diamond Member
- Posts : 1912
Join date : 2010-11-20
Location : Sweden
Re: This thing is great!!
Nice Restoration !!!!!!!!!!!!!!!!!!!
Kim- Top Poster
-
Posts : 8625
Join date : 2011-09-06
Location : South East Missouri
Re: This thing is great!!
I know these valve throttles, they are working better than their reputation.
Here is one on Ebay:
http://www.ebay.com/itm/Cox-Rc-engine-/111088472355?pt=US_Radio_Control_Control_Line&hash=item19dd639123
Here is one on Ebay:
http://www.ebay.com/itm/Cox-Rc-engine-/111088472355?pt=US_Radio_Control_Control_Line&hash=item19dd639123
coxaddicted- Gold Member
- Posts : 492
Join date : 2012-07-11
Age : 44
Location : North-Rhine Westphalia, Germany
Re: This thing is great!!
The operation of the exhaust valve is clear. I am a little unclear on what is going on with the the intake part of the show.
This is my guess from the pictures:
It looks like there is nothing to restrict the intake air as the spray bar rotates. The spraybar has a wide cut instead of just a jet hole as normal. By rotating the spraybar, the needle/seat vacuum signal varies depending on the angle the "jet" cut is making to the intake air, and this approximately corrects the mixture as the airflow varies due to exhaust restriction.
Do I have that right?
About what angle is the sparaybar flat when the trottle is wide open vs. idle. Maybe if I could impose on you to take some closeups of the spraybar showing how the flat aligns with the control lever I could work it out...but maybe you don't want to risk losing the circlip!
This is my guess from the pictures:
It looks like there is nothing to restrict the intake air as the spray bar rotates. The spraybar has a wide cut instead of just a jet hole as normal. By rotating the spraybar, the needle/seat vacuum signal varies depending on the angle the "jet" cut is making to the intake air, and this approximately corrects the mixture as the airflow varies due to exhaust restriction.
Do I have that right?
About what angle is the sparaybar flat when the trottle is wide open vs. idle. Maybe if I could impose on you to take some closeups of the spraybar showing how the flat aligns with the control lever I could work it out...but maybe you don't want to risk losing the circlip!
kevbo- Silver Member
- Posts : 91
Join date : 2013-03-05
Re: This thing is great!!
When I get the engine back on the bench I'll see if I can get any good pics of the spray bar in the high and low throttle positions.
The Distracted Mark
The Distracted Mark
batjac- Diamond Member
-
Posts : 2375
Join date : 2013-05-22
Age : 61
Location : Broken Arrow, OK, USA
Re: This thing is great!!
The flat part is paralel to the flow of the air at full throttle, and it restricts the airflow a little at lower settings but not as much as it would have to on a regular intake throttle without an exhaust restriction. The exhaust restriction would be enough for throttling on its own, but the intake needs adjustment too inorder to not loose all the fuel draw at the lower airflow, I guess.
Surfer_kris- Diamond Member
- Posts : 1912
Join date : 2010-11-20
Location : Sweden
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