15-08-2014, 12:40 AM
I did a bit more work on the engine over the last week.
There's a bit of an issue with the OS engines getting hot in the MXSR airframes. I'm not sure how much this has to do with the design of the cowl or how badly the ASP engine would suffer temperature wise in the Harmon Rocket airframe. However I'm not going to take any chances as I'm asking the poor ASP to put out a bunch more herb than one of the OS 120 specials, hopefully it will comply. If it does it will certainly generate more heat and that will need to be dissipated.
I was rather unhappy with the shape of the original combustion chamber in the ASP, It didn't take much to see that it wasn't going to cut the mustard as far as my idea of performance goes. So I was resigned to making a new head for it. The initial thought was to make a button and machine the underside of the original head flat and re-use it as both, the retaining clamp for the button and the heat-sink. There are a few engines made like this. I was thinking this might not be the best solution because heat may not be conduct away as well via a clamped on heat-sink compared to a head manufactured from a single piece of metal.
It was Micky T who provided the inspiration for the totally new head because he brought a thunder tiger Heli engine along to the last indoor flying session and one look at the way the head was set up on that set the gears in motion for designing a 120 size version for the ASP.
Here's some photo's
Roughing out, the new head begins to take shape
Putting the narrow deep groves in between the fins
The combustion chamber is carved out to the carefully calculated dimensions
bolt holes are drilled in the right place
Glow plug hole is tapped and a bit of an extra air slot milled in on top
It all seems to fit OK and it definitely has a lot more cooling area than the original and a much better chamber as well !!............Hopefully
Now to mod the liner a bit (the one on the right is the original) The one on the left has the exhaust duration increased a little bit
And a quick test fit to find that there's no way the standard muffler will fit inside the cowl
I'll need a bit of jiggery pokery in that department as well
There's a bit of an issue with the OS engines getting hot in the MXSR airframes. I'm not sure how much this has to do with the design of the cowl or how badly the ASP engine would suffer temperature wise in the Harmon Rocket airframe. However I'm not going to take any chances as I'm asking the poor ASP to put out a bunch more herb than one of the OS 120 specials, hopefully it will comply. If it does it will certainly generate more heat and that will need to be dissipated.
I was rather unhappy with the shape of the original combustion chamber in the ASP, It didn't take much to see that it wasn't going to cut the mustard as far as my idea of performance goes. So I was resigned to making a new head for it. The initial thought was to make a button and machine the underside of the original head flat and re-use it as both, the retaining clamp for the button and the heat-sink. There are a few engines made like this. I was thinking this might not be the best solution because heat may not be conduct away as well via a clamped on heat-sink compared to a head manufactured from a single piece of metal.
It was Micky T who provided the inspiration for the totally new head because he brought a thunder tiger Heli engine along to the last indoor flying session and one look at the way the head was set up on that set the gears in motion for designing a 120 size version for the ASP.
Here's some photo's
Roughing out, the new head begins to take shape
Putting the narrow deep groves in between the fins
The combustion chamber is carved out to the carefully calculated dimensions
bolt holes are drilled in the right place
Glow plug hole is tapped and a bit of an extra air slot milled in on top
It all seems to fit OK and it definitely has a lot more cooling area than the original and a much better chamber as well !!............Hopefully
Now to mod the liner a bit (the one on the right is the original) The one on the left has the exhaust duration increased a little bit
And a quick test fit to find that there's no way the standard muffler will fit inside the cowl
I'll need a bit of jiggery pokery in that department as well“The knack of flying is learning how to throw your machine at the ground and miss.”
"When once you have tasted flight, you will forever walk the earth with your thoughts turned skyward, for there you have been, and there you will always long to return." ~Leonardo Da Vinci