Thursday, December 29, 2011

Will my tractor be quality?

A college buddy of mine Michael Senkow, asked about my tractor. He said:
are the new tractors as good as professional ones? Part of why the expensive ones cost so much is their long term life right?....will these last as long?
Here is my answer:  I can make a tractor that is categorically better than a professional one.

That tractor is called LifeTrac. Here is my reasoning...

This is a four minute TED Talk in which the founder discusses his experiences with 'industrial quality'.

For me, this resonates. My experience of commercial products from our economy is almost universally dismal. I'm not surprised to hear an experienced farmer say that modern tractors are fragile.

What does my tractor have to be to be better? It has to have a long life with generally low maintenance costs. It must be versatile enough to do the jobs I need to do. It must be affordable to produce and safe enough to operate.

Long Life: LifeTrac is built with very heavy duty materials. Commercial ventures skimp on materials because consumers don't generally differentiate between a product that lasts 20 years and one that lasts 50 years. I've had too many tools break because of this kind of skimping.

Maintenance Costs: LifeTrac will be maintainable for a couple of reasons. It's very modular so one broken part can often be replaced on the spot with a spare. The tractor keeps working while the broken module goes to the shop. Each module is inexpensive too. I expect to repair or replace any module on my tractor for $500 or less. I probably couldn't get a professional tractor to the shop for that much.

Versatility: LifeTrac uses the Bobcat standard for bucket attachments. Additionally, it has auxiliary hydraulic power connections which can be used to attach arbitrary machines. The power module on the LifeTrac can be removed and replaced with a more powerful one. It will be able to do any job an equivalent commercial tractor can do.

Building Cost: I expect my LifeTrac to cost around $10,000 to build. That is about a quarter the price of a commercial tractor. Factor-e-Farm is already selling them for a profit. I don't know how many hours of labor it will take to build. I've already put a lot of time into the project and there is a long way to go. I'm tracking my time and money costs. I'll report on total costs when I'm done.

Safety: All heavy machinery is dangerous to operate. LifeTrac will be safe enough when operated carefully. It may be less safe than industry tractors-- I don't know enough about safety to judge.

The Long Run: Open Source projects improve and grow as they get more contributors. As more people build and use LifeTrac the failure modes, and inefficiencies will become apparent and the design will be improved. This will likely reduce cost, extend lifespan, add functionality, and improve safety.

Monday, December 19, 2011

2 Weeks, 1 Post. That's efficency.

My Christmas present to you is a post! I worked on Dec 8th and 15th. On the 8th I made my biggest mistake yet. You may recall that I had two flanges left to weld onto the hydraulic tank. On that faithful day, I welded both into place. Then I tried to screw in their hydraulic fittings. The top flange got a breather cap and the side flange got a male to male adapter:
Breather Cap on Left, Male to Male adaptor on right
That was the plan at least. The side flange went in just as planned. See it here:
The grey is the tank, the teal is weld and the green is the flange itself
The top flange went in like this:
Can you tell what's different? The flange is upside down. I could screw the breather cap in from the inside of the tank but it wouldn't fit from the outside. This was the state of affairs at the end of the 8th.

With a week to think about it, I decided I would skim the surface of the tank with a cutting tool and go back to square one. In the shop on the 15th I tried that and found that my cutting tool was too dull to cut through the weld (which was made of stainless steel). So I switched to old faithful: the boring head.

I would cut out the flange and weld on a new one. Half way through my first pass with the boring head I stopped. I had an idea! This was the situation:
What would you do? I decided to back off the cutting head and clean out the threads which were buggered a bit by the cut I'd just made. After that, the cap fit!

It probably saved me two weeks of recovery work. I hope you like my diagrams, they were fun to make. The whole process may seem clean by my description above. It was actually pretty messy. I got to practice clamping again-- here is my rig:

A really tall clamping arrangement

I finished my machining course, so I won't be working on the Power Cube until the spring semester. During the down time, I may write down my thoughts on why this is worth doing.

Time Card updated.

Sunday, December 4, 2011

Dec 1 - Cleaning and Welding the Reservoir

December 1st was another day with big plans. The reservoir tube was finally cut to spec. It was time to weld again. But first the tank needed to be cleaned out. Below you can see the specks of rust from the light rain that was falling when I carried it into the shop.

Mr. Lyons suggested that I clean off the inside with Scotch Bright. As I did, I noticed a lot of black dust coming off of the tube. It collected as a dusty shadow on the ground. I'm glad this stuff won't be running through my tractor.

Scotch Bright getting dirtier
Junk from the tube interior
To keep the interior from degrading I coated it with WD-40. This will prevent rust while I'm finishing the production.

Next I took the angle grinder to all the surfaces that I was going to weld (to take off the mill scale). Then I ground a chamfer into the flanges. This is a small angle that will allow fill material to flow between the surfaces that I will weld.

Ground and ready for welding
It turns out that professionals assemble gas tanks and other water tight things using TIG welding. TIG is a stick welding technology that gives extensive control over a weld. You apply heat and add material separately. This means that as you weld, you can backtrack and fill holes.

I decided to use TIG instead of MIG for this job. First I welded the large flange to the standoff tube. It went well except for a mild burn to my leg and a crater from my attempt to weld without any shielding gas.

The first section of the weld. The tip of the TIG gun is visible shown.
You can see that the chamfer leaves a gap between the flange and tube.
This is what happens when the shielding gas isn't turned on.
Fortunately you can weld back over the spot pretty easily.
I finished the flange and then welded the tube to the tank. I forgot to get a picture of that. I'll include that next week. I'm pretty happy with the product, the welds look good and are almost certainly air tight and very strong.

* Timesheet updated