aspeed

I wouldn't do the facing off on an OS with the nickel plating that goes all the way around the outside of the liner. The normal chrome with the masking is ok. I would make sure the burr is off when you are done, so the head sits flat.

Mr Cox

I prefer to remove some material from the head instead, that works on the OS engines too. One just has to be careful with the inner corner, there cannot be too much of a radius there or it will interfere with the top of the liner.

aspeed

Yes, but it is more difficult in a lot of cases, with odd shaped heads, and with a groove cut for the shim in a lot of the OS heads.

Mr Cox

The groove for the shim doesn't really serve any purpose I think, and it can simply be removed.
It only reduces the visible gap between the cylinder and head a little...

Pond Skipper

Ok getting back to this design er build project we had been discussing the ASP .12

MA 5.75 x 4 26k Chucks fast 100+ mph plane to APC 6 x 4 on a speed delta vid previously posted getting 27k with a modified ASP .12 from a friend you know.

I have looked into a MAC .10 to .15 size header as I already had the .10 to .15 pipe the header came in they recommended 3.5in cut but to add 1 in to be safe and test cut test cut 1/4th inch at a time till you max out the rpm .

If for the Lil Miss plane I would like to use the pipe for the torque and swing a APC 6.5 x 5 pylon prop
for vertical thrust with the 5P for some speed - shown in the pic.

I have not checked the timing on this engine yet - Chuck did you ever check the exhaust timing on this engine?
Here is a pic of the set up with the header pipe cut to 4.25"

Since the Lil Miss will be rather robust with a ply skin shell and in lieu of the weight of the landing gear the extra power would be nice although the Slim V could do with this engine too with a 5.5 x 5 for speed.
I just got finished watching a OS .10 on this MACS tuned pipe system it was a big improvement over stock. The Header Part 2040 (Standard) is set up for the Enya .11 CX and OS engines .010 FSR to .15's / .12 CZM yet the bolt pattern is a perfect fit for the ASP .12

combatpigg

My Feedback: (3)

I recall checking the ASP .12 but don't remember the exact figure.
It was probably in the 160 degree range.
The first step is to get open exhaust readings for your bench mark.
[5.75 x 5.75] x 4.25 = 140.51 load factor. Sounds like a winner
[5 x 5] x 5 =125.....could work with your plane but static thrust is weak. Good prop for bench runs.
[6 x 6] x 4 = 144....works surprisingly well.

Mr Cox

How much of an improvement did you see on the OS .10?

With the stock timing on the OS .10 FP I have not seen any gain over an open exhaust by using the MACS tuned pipe. I got much better results by using the MACS header and an after muffler from Merker instead. This matched the open face numbers (16500rpm on an APC 7x4) while running very quiet and throttled well.

The ASP timing varies a little between different engines, but they are around 150° in exhaust opening. My best one has a little machining error in the port, making it close to 155° which I've increased to 158° with a shim under the cylinder. This one now does 17200rpm on the APC 7x4, using the stock muffler.

Pond Skipper

Thank you Chuck - I dont know much about load factor math what are you looking for there?
Yes will do some break in time then hit the coals with just the header pipe and with stock muffler perhaps open exhaust it will be very loud will have to get away from the local life forms to do that. Will rig up a test stand and to it to the flying field with two of my photo cell tachs.

If 160 x 1700 / 25,000 unloaded (for reasonable engine life) will need about 10.88" from the center of the cone to cylinder wall / perfect as with my flex ruler it's at 11.25" now after cutting the header pipe. I will use APC 5.5 x 3 should give me near unloaded rpm on the bench?

If I recall in the hand you was getting 22.6k with the cut down MA 5.75 x 4 - I imagine you used 10% or 15% nitro?

Thank you Kris - edit is needed then:

If 150 x 1700 / 25000 - will need about 10.2" - I will have to use this header / pipe set up was about 50 bucks all together plus engine. 46 if I recall so just under 100 bucks worth of vroom vroom.

OS .10 LA / 2008 - In the vid he was getting over 18k after the pipe with a MA 7 x 5 / 15% nitro.

I imagine you was using 10% nitro Kris?

Mr Cox

Yes, my figures are with 10% nitro and 20% all castor in the fuel.

I wouldn't trust everything you can find on the web, if it sounds too good to be true then it probably is...

+18000rpm on a 7x5 prop, sounds like a .15 engine to me. The .10LA will never make that kind of power.

Pond Skipper

I found the vid and did a audio tach read 16.472 to 16.876 rpm perhaps he meant unloaded in the air.

https://www.youtube.com/watch?v=Ie4AQFJyEZA

https://www.youtube.com/watch?v=Ie4AQFJyEZA

Mr Cox

It sounds similar to the results I had with the APC 7x4 then. The engines turns similar rpms to an open exhaust configuration and it never gets on to the pipe, don't think that it really can do that either with the modest exhaust timing. On the Topaz .12 engine I have seen a little tuning effect but it is based on a car engine and has an exhaust timing of around 158°.

Sure most engines rev more than they would with the stock muffler, but there is no real power increase.

combatpigg

My Feedback: (3)

I just bench test the prop I intend to run and make adjustments to the pipe length and the weight of the prop blades until I have something that is worth taking to the field for test flights.
I don't pay too much attention to pre-tuned formulas, except it's good to know that you have ample length before you start hack sawing 1/4" chunks away. If the gains are small, then the bulk of the prop is holding things back. When you're done, the result should be an improvement over the open exhaust reading. If not, then you aren't running a tuned system, just a muffler.

aspeed

Yes normally you pick a prop in the range you think or calculate to be about right, and then adjust the pipe to get on the pipe on the ground. Then you shorten it a bit so it will be hooting when the motor unloads in the air. A pipe is still much better than a muffler in any case, usually even if it is not fully adjusted. The tweaked Russian ones may not be the case, but most sport oriented pipes are like this. The old Rossi pipes had O ring seals that were adjustable. Now they seem to just use hack saws. Kind of crude, and non reverseable. Just for comparison, and because it made me happy when I ran it, my Picco .12 ran a 7-5 MA prop at 18,300 unmuffled and with the pipe from an Ucktam it picked up to 22,000. With a muffler, I would guess a loss of 1,500 from the 18,300 could be expected, and would be similar to most .15 size motors. 22,000 is better than every .15 that I have, which is more than a sane person would need. The Picco was fairly mild timing from memory which is failing.

aspeed

Just thought I would add something I thought was interesting, and wanted to try for quite a few years. I am still looking for some thin wall aluminum tubing for it. Hmm maybe it is over 20 years now. or 30?

Pond Skipper

Thanks for the tips and findings gents

I put the degree wheel on the engine it is showing 150 with a positive seal a few ticks past that. I use a nice little no fuss pipe cutter lol no hack saw or snarled aluminum / it does pinch down the lip some then use steel flaring tool to straighten / smooth the ID back out ...so will just do a open exhaust test and any rpm gains above that will have to be considered tuned.
Need at least 600 rpm on the ground in hopes of a solid increase in the air the engine needs to support the additional weight the pipe / header 61.4 g / 2.14 oz
I'm down to my last thin walled pressure fitting those puppies are not cheap crazy prices these days.

Pond Skipper

Retrospect the 1/2A pipe system ended up at 19g