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Old 03-05-2019, 10:16 PM
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Update

There are a couple of items still open for testing:

As the bottom half cools after mating with the top half, there is some shrink back of both top and bottom case sections. Thus when relieving the pressure off of the 4 bolts holding the case together, there is a separation of .004 to .006 Inches in excess of the thickness of the gasket. You can see this in post 111 where you see the .004" feeler gauge fit in between the two case halves. This picture was taken prior to disassembly of engine 3. The shaft also stretches as it warms up but it should be minimal. I will try to cool the hole front end and place the rear end on hot on my next trial to see if this issue duplicates and if there is a benefit from doing so.

The intermediate bearing sticks out by .008 further out into the case than on engine 1 and 2. Remember, engine 1 and 2 did not have a gasket. To maintain the centerline of the rods to the cylinders, the shaft has to be pushed towards the rear by .008 to make up for the additional thickness of the gasket. The intermediate bore of engine 3 is .008" shallower than engine 1 and 2. I will post these measurements and pictures when I take apart the reassembled engine3.

When putting together mechanical components one has to always be mindful of the stack-up component dimensions. So if the shaft is moved by .008 to the rear, the gap in between the prop hub and case will also change by .008.


As you all know, I do not fly this size motor, so I am making a test stand to test an breaK-in this engine. The DA manual specifically asks the user to break-in while flying.

This is due to the lack of air flow around the heads and the tightness of the rings prior to seating them properly.

To avoid this issue, I am looking into making some modifications in the test stand:

1-add a sheet metal baffle if I can around the heads
2 -Add 2 , 5/8" air multipliers to the front of the baffle. These venturi devices, take compressed air, and through velocity create a large suction on the other end. Thus a 10 CFM compressed air flow, can result in 100 cfm of flow out to the engine. See pdf below. This is one of the units I am looking at as I am trying to figure out how to attach such item and space requirements.

I purchased the following do it yourself header parts from DA to go along with the cans I have.

In addition I am looking for 2 SEcraft aluminum 80 mm mounts ( Secraft has only one in stock)and am looking to buy some standoffs as the engine is too close to the stand.

I will post a video of the header brazing as this has been a hot topic this weekend when I get everything in.


4x Couplers / Clamps - 28mm clamp for $2.00 each
2x Couplers / Clamps - 28mm coupler for $6.00 each
3x Do-It-Yourself Headers - 28mm Long Tube for $5.50 each
4x Do-It-Yourself Headers - 28mm 90degree for $7.50 each
4x Do-It-Yourself Headers - 28mm Short Tube for $3.00 each
2x Do-It-Yourself Headers - DA 150 Flange w/stub for $14.00 eac

I purchased the two cans to cut open and attempt cleaning them in the ultrasonic bath I have. I purchased these two cans from fellow member Andrew Campbell and want to thank him for his help with my projects. At the end of this, I will cut these cans and work to find a good cleaning solution. Better Living Through Chemistry
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Old 03-07-2019, 03:26 PM
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Update

Received header tubing and brazing rod from DA this morning. As usual, they are very fast on delivery, thank you.

I am still waiting for the canister brackets from ESPRIT tech as they are out of stock. I have an add in our engine portion of this site to purchase a couple, but no response as of yet.

As the picture shows, I have plenty of tubing and will attempt both tig weld on a sample, but will use the braze rod for my final manifold construction. I will video both and publish in my next post.

If there is interest, I will write a procedure for both methods.

Tig welding this tubing may be difficult because of the .020 wall thickness, but on another thread this weekend, some members claimed that they successfully TIG welded the header. I may have to have a certified pipe fitter weld this for me.

The debate in TIG welding is always amps. However, it can be shown that smaller amps can lead to a higher temperature because it takes a lot longer to reach melt temperature thus overheating the part. So, it is good that I have extra tubing so I can work on developing a process.

Again thanks DA for the quick shipping and advise on brazing the SS tubes.
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Old 03-08-2019, 03:33 AM
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Thanks for an extremely interesting thread, and for sharing your experience with us. A procedure description for both the Tig welding and the brazing would be highly appreciated.
Cheers,
Mike
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Old 03-08-2019, 08:39 PM
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Inventory For Brazing- Brazing Procedure Rev1

Inventory to braze header:

1)Header Tubing-
2)Brazing Rod 1200 F melt temp with solid flux-DA
3)Acetone for cleaning
4)Cleaning container
5)Container for used Acetone- Should be clean after use as there little to no grime on the tubing
6)Dremel
7)Dremel finishing wheel- Part No 512E I believe.
8) 3M Scotch pad
9)Wire brush- burned/used flux will have to be cleaned
10) Mapp gas- Map gas will be used for the first trial as it was recommended and it is what probably most people have available.
11) A stand to hold tubing while parts are brazed
12) Safety equipment (should have a fire extinguisher near by), glasses, gloves.

I will try to do a sample in the morning and generate a final procedure

1)Using the Dremel tool and finishing wheel, clean the inside of the flared end of the tubing.
2) With either the Dremel or the Scotch pad, clean and scrape the OD.
3)Clean tubing with acetone then dry.
4)Place your tubing with the flared end pointing up in your vise or holder.
5)Insert the straight portion of tube to be brazed into the flared end. Make sure that you are maintaining the geometry that is necessary for your set-up.
6) If the tubing that you are using does not have a flared end and you are going to do a but splice, place your two pieces on a v-block or such supporting device and tack the two pieces together with the braze rod in a few locations. The v-block will insure alignment.
You can have .010 to .015 separation. If you have this geometry, it is important not to overheat as the braze will flow through the space in between the two tubes.
7) The braze rod purchased from DA should flow very well and no damage should be encountered
8)Heat the two tubes moving the flame. More heat should be concentrated on the flared end as the solder and flux will be drawn into the connection.
9)You will know you are reaching temperature, as the tube will start turning blue before turning red. When you see an imminent glow, remove the flame and oscillate back and forth on and off the part.
10)Place flame on the rod at the juncture of the two tubes and melt some flux on the connection. You should see the flux sweat and melt just prior to the solder melting.
11)Continue oscillating the flame on and off of the part and rod to insure that you don't over-heat the tube.
12)When penetration is complete and the part cools a few hundred degrees, use the wire brush to clean the connection.

I will verify this in the morning and let you all know
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Old 03-08-2019, 08:51 PM
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the ks rod DA sells goes on like butter. you wont have any issues. You can make your own can holders with a fly cutter or a hole saw, some ply and some silicon tubing.. as far as that goes a small spring and a block of wood will work too. you can wrap the spring with some glow fuel tubing cut on a spiral to keep it from marking the cans..
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Old 03-08-2019, 09:22 PM
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Quote:
Originally Posted by 2walla View Post
the ks rod DA sells goes on like butter. you wont have any issues. You can make your own can holders with a fly cutter or a hole saw, some ply and some silicon tubing.. as far as that goes a small spring and a block of wood will work too. you can wrap the spring with some glow fuel tubing cut on a spiral to keep it from marking the cans..


Not a bad idea!!!!!!
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Old 03-08-2019, 09:59 PM
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ChenE,

You might consider moving this brazing / welding info to a new thread so the content isn't buried in your previous engine thread. This info is important enough to deserve its own thread.
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Old 03-08-2019, 11:16 PM
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Quote:
Originally Posted by Truckracer View Post
ChenE,

You might consider moving this brazing / welding info to a new thread so the content isn't buried in your previous engine thread. This info is important enough to deserve its own thread.
I have started another thread on this topic only!!!!!

Thank you all.
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Old 03-15-2019, 10:58 AM
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Starting to complete Test Stand

The manifolds are finished and I cut an 8x8 piece of hardwood for a base. Still need to finish clamps that hold the cans.

Once I finish the test stand, I will put together engine one, and fire it up on the first good day in New England.
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Old 03-16-2019, 09:30 PM
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Free OS 873 muffler

Hi all.

Cleaning my shop today and I came on a new OS muffler that I never used. Will send for free to first guy who wants it. I will ship mid next week as I am all out.

I no longer fly this type of engine and hope someone can use it.

Please PM so we don't fill this thread. Sorry no screws!!!!




Item has been awarded . Thank you
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Last edited by ChemE; 03-16-2019 at 10:10 PM. Reason: Change in status
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Old 03-17-2019, 09:10 PM
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Update and question

Finished wood work on test stand and stained with gunstock color. The wood block is 8x8 while the motor metal mount is 7.5" wide.

Minwax gloss spray seems to be the product to cote the wood to make it gasolene resistant.

Does anyone have experience with wood finish? I need some help on this. Minwax does not offer data sheet on their products.

Everything fits well, I should have the test base finished this week.

Left to be done is can mounts, drill the metal and wood base and hold down metal frame to wood base with 3/8 x3" lag bolts, paint and stain.

One issue with this design is that it is front heavy and it needs to be held down with counterweight in the rear of the frame or strapped to a stake in the ground to prevent forward tip-over. At 60 lbs of thrust, the frame as is, is unstable. I may have too make a different leg design similar to a reach fork lift to prevent tip-over
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Old 03-21-2019, 08:33 PM
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engine stand update

The stand is almost complete.

I received the Secraft can holders. I was making my own, but I ran out of aluminum and I would have had to spend $30 for a piece. At this rate it was easier to buy 2 can holders and when the project is over I can use them on a model.

Painted the metal motor mount engine paint good to 500F
Drilled holes through mount and stand for 5/16 x2 inch lag bolts
Fabricated L-shape supports for the Secraft holders
Designed a rear hold-down fixture to be fabricated and welded
Changed the leg design of the test stand to offer better support

One thing that I do not like is that I did not duplicate both manifolds exactly, so I have to adjust the size and hole location on the can holder supports
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Last edited by ChemE; 03-23-2019 at 10:07 AM. Reason: add picture
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Old Yesterday, 10:08 AM
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Fit-up before welding

I have fabricated my plate and pipe set-up and I came home to do a fit-up before welding. I could not find a 6x6 in the scrap pile so I used a 1/2 thick by 4 " wide piece. I will post welded pictures tomorrow.

I wound up using 1 1/4" NPT pipe and 1" NPT pipe for this base



Welding 1/8" 7018 stick weld at 85 amps. I should have cut the threads off and did not think it through as the first three turns of the thread make the pipe thin in that area. I needed 2 passes where 1 should have been sufficient. Must welf quickly !!!!! Also had a lot of splatter which I did not like.

I may use rebar with a 90 deg bent handle as a stake so it can easily be twisted for removal from the ground.
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Last edited by ChemE; Today at 07:28 PM. Reason: addition
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Old Yesterday, 11:19 AM
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Well done! Your test stand looks plenty sturdy.
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Old Yesterday, 12:06 PM
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The only thing i have missing is a baffle to keep the engine cool and an aluminum spacer between the engine and the frame so different size engines can be mounted without making the back-plate into swiss cheese. I also have to paint the pipe a bright color to reduce trip hazard. On this engine the prop is 30 inches so I have to walk around anyway to keep clear. Definitely will not pass OSHA standards.

I will be doing one more engine assembly trial before putting together engine 1. In this trial, I will put the whole front case end in the freezer after assembly and mate it with a hot rear case.

I am also debating purchasing a small Blue M oven to keep the parts warm right where I work. This will cost $200 and I don't do this enough to justify the expenditure. As we saw, the torch and temp stick worked well enough.
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