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A Spring Assisted Helve Hammer

Jason Jones

Last Resort Blades.

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Table of Contents

Abstract ………………………………………………………………………………………………………… 3

Safety Concerns …………………………………………………………………………………………….. 4

Introduction ………………………………………………………………………………………………….. 5

Fabrication Procedure …………………………………………………………………………………... 7

Summary ……………………………………………………………………………………………………… 16

Tools Used …………………………………………………………………………………………………… 17

Bill of Materials/Cost List …………………………………………………………………………….. 18

Blueprints ……………………………………………………………………………………………………. 19

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Abstract The power hammer is a tool of immeasurable value to the blacksmith. It is a force multiplier with the ability to perform drawing, reducing, forming, cutting, and welding operations in the fraction of the time that a man can. It provides both a labor savings as well as increased production time. With the doubling speed of technology in an era of mass production and disposable consumer goods the small shop blacksmith is relatively uncommon today. With commercially manufactured power hammers in low demand they are only manufactured by a few companies. Due to high cost of materials and expensive tooling for limited production runs these companies demand a premium for their products which is out of the reach of most single smith shops. Detailed herein are the plans for a small compact power hammer which can be built by most small shop blacksmiths for about 15% of the cost of a commercially available unit.

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Safety

Hot things burn, sharp things cut, and anything that moves has the potential to pinch, crush, or abrade. Always use appropriate personal protective equipment.

The author of this document is not an engineer. It is the users’ responsibility to ensure their own safety while constructing or using this hammer or any variation thereof. By using these plans the user holds blameless the author for any injury to himself or others.

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Introduction In designing a power hammer there are many factors to consider. Size,

cost, complexity, striking power, blows per minute, variability of power and speed, and, never to be ignored, aesthetics are all determining factors in what kind of hammer is best for you.

Size: While we all wish it wasn’t a consideration size is probably the first factor that must be considered by most small shop smiths. My own shop has a low ceiling, which rules out the Little Giant and Clay Spencer type overhead linkage power hammers as well as most guided helve and spring type hammers. For my shop and space limitations the unguided helve was a natural choice and by chance also pleased my aesthetic sensibilities for a hammer that appears traditional in form.

Complexity: The simplest of helve hammers to construct would be the DaVinci cam hammer. These are gravity hammers with the helve raised by a rotating cam and then released to fall on the work piece. While these hammers are simple, which is always appealing, the short length of stroke does not allow sufficient time for the hammer to gain maximum velocity and as such makes them extremely inefficient. E=mv2. That is Energy is the product of Mass times Velocity squared. In this equation Velocity is of exponential importance to maximizing the ultimate power of the hammer. Speeding up the hammers down stroke is critical. As such I decided to incorporate a Dupont linkage into the drive mechanism of this hammer. The Dupont linkage is a horizontal toggle spring linkage. By collapsing the spring when both pushing and pulling the mechanism is able to store energy on the push (up) stroke which is then released on the pull (down) stroke to accelerate the helve arm with a whipping action. While more complex to construct than most other spring assist linkages the Dupont type linkage has proven itself to be an industry standard in mechanical power hammers.

Power, Speed, and Variability: While the spring assisted helve hammer has a small footprint and is able to produce extreme energy outputs it is not a particularly variable hammer. When an overhead linkage hammer is at rest the hammer and anvil are not in contact. The linkage pulls the hammer up and throws it down competing to overcome the spring tension on the down stroke to extend the linkage and make contact with the work piece. Through a clutching

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mechanism the hammer can produce light slow blows to fast hard blows. While this helve hammer has a similar linkage, and clutching mechanism it requires increased clutch engagement to push the weight of the hammer up. So, while the speed of the stroke can be varied from zero to maximum, like an overhead hammer, the minimum power output is greater because the down stroke is always assisted by the spring mechanism. Not fighting to overcome it. As I intend to use this hammer primarily for drawing, reducing, welding operations this heavier minimum strike for heaviest maximum strike tradeoff was one I was willing to accept.

Cost: As detailed in the Bill of Materials/Cost section purchasing mostly new materials this hammer cost just shy of $1500. This is a mere fraction of the cost of any commercially available power hammer, and the cost could have been reduced significantly more had I been willing to take the time to scrounge for materials at the local scrap yard. Due to time restraints however, I opted to buy drops when they were readily available but come out of pocket for the primary materials.

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Fabrication ProcedureAs a whole this hammer may seem like a complex mechanism with multiple

moving parts which must align and function within a confined space. If one, however, takes a step back and views each piece of the construct individually the task at hand becomes much simpler. While these plans may be followed in hole to reproduce a hammer just like this one it is expected that most builders will deviate largely from these plans using materials that are locally available at best cost. As such I will proceed with what comes to mind as the key considerations for using these plans as a concept guide for building a similar hammer.

I will address this construction in three phases. Starting with the hammer and anvil mechanism, followed by the drive wheel and linkage mechanism, and lastly the motor mount and treadle.

Phase 1:

The Anvil:

- The first decision to be made in constructing this hammer is the desired height of the anvil. A rule of thumb for anvil height is the distance from the smiths closed fist to the ground when he is standing erect with feet shoulder width apart. Once the height of the anvil has been determined all other measurements follow.

- The second consideration is anvil weight. The heavier the anvil the more energy is transferred into the work piece, and not the ground. A good explanation of this can be found at http://anvilfire.com/power/power-hammer-building.php, where the author sites, “To understand anvils you need to imagine them floating in space. If the anvil is the same size as the hammer, when the hammer strikes the anvil will fly away at the same velocity that the hammer struck it, and the hammer will stop (like pool balls). If there was work between the two the work would move but very little energy would go into the work. If the anvil is only twice as big as the hammer it will move

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away at about half the speed. Double the energy would go into the work. So if one of these small anvils is resting on the ground or floor all that energy is transferred into the ground and wasted in vibration or noise.” My original plans called for a 10” solid round anvil. It would have weight nearly 800lbs. Unfortunately, unable to find a drop this size it would have cost almost $1k. So I went with as many 10” round drops as I could find and a 6” round for the rest. I highly recommend to the builder that they build the heaviest anvil possible.... but by no means consider sand or concrete filled tubes.”

The Hammer and Helve: When at rest the hammer should be in contact with the anvil the helve arm in a horizontal position.

The Helve Post: Either through mathematical procedure or bracing or hanging and measuring the helve post should be of a height to support the helve arm and hammer in the above stated horizontal at rest position.

Procedure: Each of these parts; the anvil, hammer and helve, and helve post, should be fabricated individually before any assembly onto the base plate takes place. Once the three parts are made they can then be assembled and positioned on the base plate prior to welding to ensure proper alignment.

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Phase 2:

The Dupont Linkage:

- The Dupont linkage is by far the most complex part of this mechanism. My suggestion when building it is to first fabricate the Helve Bracket, which attaches the Dupont linkage to the helve arm. Bolt this bracket into place on the helve arm (using grade 8 bolts) so that it is available to test fit the pivot action of the linkage arms during construction.

- The spring used in the Dupont linkage is not listed in the Bill of Materials/Cost List. It was scavenged from a dirt bike spring-over shock, Any similar spring should work sufficiently. This one is 9” long with a 3/8” coil.

- When building the Dupont linkage drill and fit the drive link bracket but leave the drive link rod until after the other items in this section are complete.

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Drive Shaft Support:

Once the Dupont linkage is built and hung in place move on to the drive shaft support. Ensure that the height of the support is sufficient for the tire that you use to clear the ground when mounted. Install the bearings and use the assembly tacked temporarily in place under the Dupont linkage to determine the appropriate drive shaft length for your hammer.

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Drive Shaft and Flywheel:

- Once the Drive Shaft Support is tacked in place identify a rough length for the drive shaft. If using hot rolled solid round stock as I did the shaft will need to be polished on a lathe to fit to the bearings. Drill and tap the drive shaft drive wheel end and turn the drive shaft friction plates and test fit up the assembly and drive wheel ensuring the wheel clears the ground. With the drive shaft in place you can now hang a plumb bob from the Dupont linkage to align the driveshaft under the linkage and mark the location for the flywheel rod end and identify the length of shaft required to place the flywheel rod end directly under the linkage.

- Once the flywheel location is identified the center hole for the flywheel may be drilled. Remove the driveshaft from the bearing assembly and weld the flywheel in place. Turn at least the flywheel face on a lathe to ensure concentricity. Drill and tap the rod end mount hole.

- After turning the flywheel drill and tap the rod end mount hole. The (Keep in mind that the diameter of the rod end travel will dictate the length of stroke of the hammer. With the Helve Bracket at the middle of

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the helve the hammer stroke will be approximately 1.5 times the rod end travel.) After installing the rod end re-install the drive shaft in the bearings and align the rod end under the Dupont linkage.

- With the rod end now in place you can best measure the length of the drive link rod. With the hammer at rest on the anvil the Dupont linkage toggles should be in a neutral or slightly loaded position when the rod end is bottom dead center of the flywheel.

Procedure: As in Phase 1 each of these items should not be fully welded into place until all parts have been fabricated and aligned. Once the parts are aligned tack them in place and cycle the hammer manually, by turning the drive wheel, to ensure that the Dupont linkage does not pivot into the helve arm, that the toggles do not strike the spring, and that the assembly is properly aligned. If the Dupont linkage strikes the helve arm reverse the direction of rotation of the flywheel. If the toggles strike the spring a stiffer spring is needed.

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Phase 3:

Treadle Pivot and Levers:

When building the treadle, the first thing to do is to mount the bearings to their supports and install the cross shaft. With the cross shaft installed locate the supports on the base plate. (The ideal location for the cross shaft is at least 2/3 the distance towards the helve post to gain mechanical advantage when the treadle is depressed.) With the cross shaft in place locate the treadle lever bars. Ensure that the bars reach past the anvil and support bracket without obstruction.

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Treadle:

With the cross shaft and lever arms in place build your treadle. Ensure that it is sized/shaped so that it does not hit the drive wheel when in a full up position.

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Motor mount:

Once the treadle, lever arms and cross shaft are all in place align the motor and mount so that the motor moves freely, is not struck by the flywheel, and so the motor spool contacts the drive wheel when the treadle is depressed.

Procedure: As in previous sections do not fully weld any of these items in place until they are all placed and aligned. Once the treadle is fully mounted and the hammer operational, check the base plate for warpage. It is likely that when welding the cross shaft support brackets in place the base plate will have cupped a bit. This will pull the helve post closer to the anvil and move the hammer head out of alignment with the anvil top. Using jacks or weights press the base plate so that the hammer head is in alignment and install diagonal supports each side of the anvil and helve post. These supports will increase overall platform a stability and strengthen the entire structure.

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Summary

This hammer is the product of research and experience only, not formal engineering training. From conception, through design and construction to completion there were modifications made as necessary based on material availability as well as mechanism interactions which could not be accounted for without 3D modeling. All of these roadblocks however are surmountable if the builder takes his time during construction to ensure proper fit up and alignment from one phase to the next.

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Tools Used

Hand Tools:

- Tape Measure- Silver Graphite Pencil - Straight Edge- Bubble Level- C-Clamps- Vise Grips- Compound Square- Wire Brush- Chipping Hammer- Tap & Die Set- Hammer- Center Punch- Welding Pliers

Power & Machine Tools:

- Everlast MP251 Welder- 4 ½ “ Hand Grinder- Oxy-Acetylene Cutting Torch- Iron Worker- Vertical Mill- Lathe- Drill Press

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Bill Of Materials/Cost ListPC QTY Description Length Weight Cost

1 Ø 6” 29” 232 344.711 FL 1” x 6” 12” 21 33.951 FL 3/8” x 6” 24” 16 25.631 TS 6” x 6” x .375 32” 74 88.981 SQ 2” 30” 34 41.621 Ø 2 6” 6 19.091 Ø 1 56” 13 18.862 FL 3/8” x 1” 56” 12 29.071 TS 6” x 2” x .375” 20” 29 42.037 Ø 10 1 ¼” 196 98.001 PL ½ “ x 20 40” 114 56.701 BIP Ø 1” 18” 8.491 Thread Locker 9.994 Hardened Pin 4” 23.771 Top Link Pin 6” 5.941 Power Cord 25’ 25.171 Plug End 13.381 Start Stop Station 29.951 Wheel Hub 24.952 1 ¼” Locking Pillow Block 31.902 1 ¼” Pillow Block 27.902 1 ¼” Shaft Collar 5.801 7/8 ” Shaft Coupler 13.951 ¾“ Rod End 15.958 1” Shaft Collar 28.802 1” Pillow Block 17.701 2HP Electric Motor 340.3040 Fasteners 34.64

Total 1457.22