Posted on February 21, 2020 @ 01:44:00 PM by Paul Meagher
I completed a major milestone on some prototyping work. My berry cleaner prototype is now ready for field testing.
The basic idea is that you pour your harvested berries into the box above which will vibrate the berries down an inclined plane so they drop as a sheet of berries in front of the air blower and into the collection tray below. The air blower should remove leaves, grass, weeds, insects, smaller unripe berries and other chaff. The cleaned berries drop into one section of the bottom collection tray and chaff (for the most part) drops into the second section of the tray. The chaff can be cleaned again if there are too many good berries in the chaff section of the tray. Various aspects of the cleaner need to be "dialed in" for it to work properly (i.e., speed of blower, strength of the vibration, height of the berry drop, shape and height of the collection trays). I've gone about as far as I can go and must wait till berry season to test and evolve the prototype.
The design of the berry cleaner is based on the design of a small mobile gas powered blueberry cleaner that is no longer being manufactured in North America. I discussed my plans to redesign the cleaner in a previous blog called Design and Redesign. In today's blog I want to discuss my experiences and thoughts on prototyping an agricultural tool. In particular, I want to underline the importance of cost, chance and collaboration in the prototyping process.
The Role of Chance
Prototyping can end badly. My attempts to upgrade my cold frame with insulation and automated heat and lighting ultimately came to nothing as the plants didn't germinate for the most part and those that did grew very slowly. Trying to grow plants in the middle of winter is always challenging and I struck out again. I literally pulled the plug on that prototype.
When prototyping does go right it may not be simply a matter of everything going according to plan. The role of chance should not be underestimated. I use the term chance instead of luck because I don't want to imply that the good fortune is entirely random. You are looking for a solution and you encounter something by chance that seems to align with your prototyping goals and you take advantage of it. Often when you are prototyping you are trying to develop functional prototypes as cheaply as you can so the materials you have to work with may be whatever you can source cheaply and may determine how your prototype ultimately functions. You may have to put yourself in a position where you might find what you are looking for without knowing exactly what you are looking for. My visit to a local metal recycling scrap yard is where I found some of the critical components I was looking for. The thingy below turned out to be a critical part of the build and I don't even know what it's previous use was. It had the springs I was looking for and the width of the legs seemed like they might straddle the air blower so I purchased it for $7.50.
There is a temptation when prototyping to immediately try to implement what you think the final version might look. That temptation should probably be resisted if there is a cheaper functional alternative that might work and provide feedback. I tested out a cheaper setup but worried that mounting a vibration motor to the underside of a tire damped the vibration too much. I also didn't like the fact that the berries would have to drop at least the height of the tire before moving in front of the air blower.
I wouldn't definitively rule out using a tire as the platform for a vibration table, but mounting the vibration motor on a sheet of plywood attached by springs to a steel frame definitely produced a more vigorous vibration and I'm comfortable with the approach I am now pursuing which is truer to the original design.
My carpentry skills or ok. My metal working skills are almost non-existent. I was fortunate that a retired handyman with these skills had to stay at my place for a few days while his wife had surgery. I may have tinkered my way to the final design we arrived at but it would have taken alot longer and, in the case of the ductwork converted to a dumping box, I doubt it would have looked as professional as the final product now looks. There is a certain jazz fusion that goes on when you are jointly building something with a vague blueprint and you have some complimentary skills. Me coming up with some critical suggestions and my practical collaborator knowing how to implement these suggestions quickly and effectively and adding his own take on how it should work.
Early on in this project I tried a couple of times to hire a metal fabricator to help me re-implement a gas powered version of the berry cleaner. One fabricator didn't want to do the project because there were too many parts and he thought he would have to dedicate most of his time searching for and ordering parts. Another fabricator simply stopped responding after initial enthusiasm. Yes you can pay for a collaborator to help you, but if you are trying to keep things cheap you might opt for someone you know with skills who might be willing to work you free. Alot of older people have skills that they are only too ready to apply to novel problems over a few cans of beer.
Prototyping an agricultural implement is different that prototyping an app but the role of cost, chance and collaboration may also be at play in determining whether prototyping succeeds or fails.