Hero Reaction Turbine Engine
By Dr. Greg Latta

Body Construction

Engine Body
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 Main Page and Introduction  Head Button Construction
 Head Construction  Jet Construction
 Body Construction  Final Assembly and Operation



Facing the End:
After the head has been cut off of the blank, the exposed end is faced to clean it up. Don't cut off much material or worry about the dimple in the center. Only the outer 1/4" will be left after boring out the center.


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Drilling the Body:
After facing the end, drill out the center with a 1/2" drill. Be sure to leave slightly more than 1/4" of material in the bottom of the blank. In other words, when finished, the tip of the drill should be at least 1/4" from the bottom of the blank.


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Boring the Body:
A boring bar is now used to bore out the body until the bottom and sides are 1/4" thick. The thickness of the bottom is not critical. However, the thickness of the sides is critical. As the thickness of the sides gets near 1/4", use the head to check the diameter. Bore only until the head makes a nice, clean fit. The head should fit nicely on top with no slop.


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Chamfering the Edges:
The final length of the body is not critical. Mine turned out to be 1.446", yours will be more or less. After boring the body, use a file to deburr and chamfer the exposed edges to smooth them, as shown in the photo at right. (A deburring tool could also be used on the inside edge.) Finally, remount the body in the chuck with the bottom out and chamfer the bottom as well.


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Drilling and Threading the Head Mounting Holes:
After the body is bored, drill and tap the mounting holes for the head.

I used a rotary table to drill the holes since it was already set up from drilling the head, but that was a gross case of overkill! (In this photo I am using a center drill to predrill the mounting holes.)

A much easier way, and probably better way, is to use the head as a template to drill the mounting holes. Place the head on the body and use a center punch to mark the location of the holes. (Use a #32 transfer punch if you have one.) Use a #43 drill and drill the holes 1/2" deep. Then use a 4-40 tap to tap the holes. (Use a plug tap, and then finish off with a bottoming tap if you have one)

Chamfer the top of the holes with a hand held 1/4" drill to remove any burrs. This ensures a tight seal for the head.


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Getting Ready To Mill the Flats For the Jets:
Two flats must be milled for the jets. These should be exactly opposite each other for the best balance. One way to achieve this is to mount a 6" machinist's rule on the body as shown in the photo. The body is then mounted in the vice so that the ruler is exactly horizontal, or as near as you can get it. (I used the depth gauge on a vernier caliper to make sure the edges of the ruler were the same distance below the top edges of the vice.) It is also very important that the top of the body is exactly flush with the front face of the vice, as shown in the photo.


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Milling the Flats for the Jets:
The body is positioned so that the center axis of the milling machine is exactly centered left to right, and 7/32" (0.219") down from the top edge of the body. Use a 5/16" center cutting end mill (2 or 4 flute) and carefully mill a flat in the side. Mill only until the shape of the flat just becomes circular, and no more.

(Though an end mill should normally be mounted in a collet or end mill holder, you can get away with mounting it in a chuck in this case since are are essentially using it as a light duty drill.)


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Drilling the Mounting Holes for the Jets:
Replace the end mill with a center drill and carefully mark the center of the flat. Then drill through with a #21 drill, and tap the hole all the way through with a 10-32 plug tap. Finally, use a hand held 3/8" drill to carefully chamfer the top of the hole to remove any burrs.

When finished, rotate the body exactly 1/2 turn (as indicated by the ruler) and repeat the entire process for the other side. Be sure the top of the body remains flush with the front surface of the vice!


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Finished Body:
In this picture of the finished body, you can see all of the essential features: the body itself, the holes on top for the head, and the holes on the side for the jets. Notice how the chamfering, besides guaranteeing a good tight fit in critical areas, improves the look and "feel" of the body.


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©Copyright Statement:
All images, designs, and materials on these web pages are the property of Gregory P. Latta and are ©2008 by Gregory P. Latta. You may use them for personal purposes and for educational purposes, but any commercial or other use is strictly prohibited unless written permission is obtained from the author.

Disclaimer:
Opinions expressed are those of the author or the quoted source. The author is not an employee of or agent for any of the vendors referenced in the text and does not sell or represent any of the products discussed. Vendors may provide products for review purposes and may provide sponsored support through advertising or links. No information provided herein represents professional advice or best practices. All information is provided to help the reader gain a better understanding of the tools and techniques described. Considerable care has been exercised to provide accurate and timely information. However the author cannot be responsible for information which is incorrect or out of date. Power tools and shop practices can be dangerous if used carelessly or improperly - always take proper safety precautions such as wearing protective eyewear and appropriate clothing. All practices, procedures, modifications and product recommendations described herein are to be used at the discretion and risk of the reader.


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