Trammel - Cardan Mechanism - Straight Line Mechanism

www.psmotion.com
When a claw hammer extracts a nail from timber, a lot of energy is expended just to bend the nail, and to rip through the timber as the nail is bent toward the fulcrum of the claw hammer. This mechanism eliminates both of these unnecessary wastages and so makes the nail extraction relatively effortless - AND it saves the nail!!!
Here, we use the Straight-Line properties of the Elliptical Trammel / Cardan Mechanism. The natural reaction force, as the nail is extracted, keeps the roller in contact with the timber. This acts as the fulcrum. The roller has virtually no friction, and therefore it rolls towards the nail in preference to the nail moving towards the fulcrum. The mechanism is equivalent to a Cardan. Hence, the nail is extracted along a straight line perpendicular to the timber - perfect to keep it nail straight and to eliminate the effort that goes in to bending the nail and in to ripping the timber.
MechDesigner model for demonstration of new concept to potential investors.

[@MechDesignerHowTo]

Thanks for your comment - It is really meant as an example of mechanism design. There are many, many elliptical trammels on RUclips - and each show just that - two slide blocks in a slide way, arranged at 90 degrees to each other. That is just a toy - at best. What I was trying to do was demonstrate an application. The design will reduce the friction force and the effort spent destroying / bending a nail as it is pulled out. I was also trying to demonstrate that mechanisms are not always apparent in their 'as built' form. Hence, it was meant to be educational. Also, I am not sure of your objection to the savings. There are people whose job it is is to reclaim timber - if this makes their lives easier they are welcome to it - let them be the judge. Also, when you want to reclaim antiques, it is sometimes nice to pull the the nail straight out rather than bend it. Also, damage to the wood is reduced both around the hole and under the fulcrum because of the reduced reaction force.

[@danellis3319]

The idea successfully reduces the friction and it does save the nail. However, those two problems are not really problems in the real-world use of a crowbar.
1. The friction is very small compared to the force needed to pull the nail. It is easily overcome by the weakest of human arms due to the leverage of the crowbar.
2. The nails are less than a penny each. It would take around a thousand of them to overcome the extra expense of the machine work needed to put wheels on a crow bar. It would take years to break even.
3. When the nails are pounded in the first time, most of the heads became slightly bent because the hammer doesn't always hit them exactly squarely every time. They tend to double over the next time you try to use them. There is no point in saving a slightly bent nail.
4. A regular crowbar is as tough as an anvil. You can beat the heck out of it with a hammer or use it to demolish concrete blocks. The wheels would make it less able to withstand such abuse.
You are obviously very smart, mechanically, but you are solving a very small or nonexistent problem. It's like installing roller bearings on your laptop's hinges to reduce the effort it takes to open it.
A fraction of the cost would be better spent by making the handle slightly longer and simply grabbing a new nail out of your nail pouch.
This may have been avoided by actually using a crowbar for a day or two (perhaps as a contractor's helper to demolish a building).
I hope you're not discouraged or offended by this criticism but rather strengthened by it. We need guys like you coming up with ideas to make all of our lives easier, faster, safer, and/or better. I hope one or more of your ideas will make you rich. The God the Christians worship will bless you if you make the world a better place.