Wednesday, March 6, 2019

Shop Update

It has at least a month since I've done one of these, so I thought I'd talk about what has been consuming my thoughts lately.

First, though, a detour.  Back in October, I posted about upgrades I was working on.
  • Build a new front onto my enclosure replacing the bifold doors, and more importantly, allowing me to get to the machine's table without scraping the top of my head on the aluminum rail
  • Resurrect the ability for my CNC Lathe to cut threads.  
  • Look at improvements to the spindle on my big mill, the G0704.  This is aimed at a few things:
    • Ability to start, and stop the spindle from the CNC code - this is fundamental in the real world.
    • Ability to set the spindle speed from the CNC code.  The GCode command exists for this and I think most all of the "real" machine shops do it.  
    • Together, these mean a new motor.  I will do this with an eye to roughly doubling the speed of my spindle.  Which will require new bearings for spindle
    • After this, I'm considering being able to tap (thread) holes under CNC control.  This one, frankly, isn't super important to me, but it looks like the I can accomplish that without adding much cost to the motor and controller improvements that do the first two.  
Of these three, I've gotten the second one (my CNC Lathe) virtually completed.  There are other types of threads I'd like to be able to cut, but it does pretty well at what it does.  I haven't actually bought Mach4 which I think gives me those other things (multiple start threads, Acme threads to name a couple).  What stopped me was filling out the "contact us" form on their website about a question I had and waiting for an answer.  Since I've long since forgotten the question, I suppose it doesn't matter.
I have the raw materials for the frame (lots of 1x2 and 1x4 lumber) but have done nothing and am thinking nothing might be the thing to do (I'll eventually use that wood for something else).  Why the change?  I guess a combination of that I've gotten more adapted to bending over to not hit my head when I go to the mill and not being sure the design is solid enough to do once.  I might still change the enclosure.   
The last one, the biggest project research-wise (and potentially rebuilding everything I have-wise), has had very little attention.  Probably 10% of what I need to do. 

What I've been paying attention to is picking the next project.  In my New Year's post, I mentioned it would probably be a simple internal combustion engine called a Webster (after the designer).  I have the downloaded prints and started putting together a materials list, but I got distracted by the call of making something bigger.

YouTuber Pat Pending's Webster engine, a build fairly faithful to the prints.  There's a lot of variation in the way builders implement this.

The prints will produce an engine that displaces 3/4 of a cubic inch.  A rule of thumb I've known for virtually all my life is that an IC engine is doing real well in power if it can make 1 horsepower per cubic inch.  I'd like to do something that generates more useful power than that (possible) 3/4 hp. 

What does "more useful power" mean?  One horsepower is defined as 750 Watts, meaning the Webster might generate as much as 560 watts.  What does that mean?  Let's assume you're in average health; that is, you don't work out in a gym and you don't do heavy lifting all day for work (no "roofercise"), but you move around with no problems, do routine housework, gardening, house-related tasks.  If we put you on a bike driving a generator, you'd probably generate around 100 to 125 watts and you could keep that up for a while.  If you're fit, you can put out more like 250 Watts - prolonged steady output - without getting exhausted.  A professional cyclist can put out 400 W for hours, and some put out well over 1000 watts for a peak effort. 

In Florida (and many other places) a 49 cubic centimeters (cc) displacement motor on a bike can be street legal and doesn't require a driver's license.  49cc is 3.00 cubic inches and the same rules of thumb tell me a "49er" could generate 3HP or 2250 Watts.  That sounds like a practical power level to shoot for; somewhere close to 3HP.  Mowers for small yards have much bigger engines than that.  With proper interconnections, it could drive a generator to charge batteries, or a water pump, or something else I might need to run after a storm or in an extended power down situation. 

To give sense of sizes, the bore and stroke of the Webster are 0.875" bore (piston diameter) and 1.25" stroke.  I've seen references to 49cc engines with 1-9/16" (1.563") bore and stroke.  The biggest hurdle stopping me from taking on the project like the bigger 49cc engine is not being able to find plans I can buy.  The biggest advantage is that there are literally tons of them on the market and I can buy some parts for less than it would cost to buy the bar stock to build the parts.  Mind you, I could buy a complete running engine for less than $80 on Amazon.


  1. My old Honda 49CC stepthrough made 4.5 HP, factory spec, on a little tiny carburetor with pump regular. Cute little hemi, with valves I could unseat with my thumbs.

    On a note from the past, it occurs to me that the power generation of a flame-eater engine is related to its displacement. A bigger one should run better, up to the point that gas transfer is impeded.

  2. 1 HP = 745.699872 watts, but who's counting

    Your "1 HP per CU" rule held pretty well until the late 20th century, but lately they've blown this out of the water with advanced engine controls, better alloys, and various super/turbocharging schemes. Some cars are actually getting over 2hp per cubic inch!

    I would expect, though, that a homebuilt tiny engine would struggle to achieve 1/2hp/ci, so good luck. I was going to point you to a nice little 80cc 2-stroke I ran into the other day, but then I read a little closer and realized you had already linked to it. It might be fun to buy two or three of those and try to hook them together into one engine, like the Russian idiot who bolted three together end-to-end to get a 12-cylinder (a Lada: ).

    There are all sorts of ways to waste one's time in retirement... ;-)

    1. Back in the early 80s, I had an outboard that was rated at 115 HP and the manuals said it was just about 115 cubic inches. I think it was a V4, and a two stroke (it was before 4 stroke outboards were available, AFAIK). That was my high water mark.

      I'm embarrassed to say I don't recall an 80cc 2-stroke.

    2. If you are TRULY masochistic and want to build an engine from scratch, then The mastiff is a good one:

      From here:

      Or, if you want to build a stationary steam engine, Camden Miniature Steam is a good source of information. ( One of my friends and I discussed building one to power a steam launch and seriously (to the point of drawing up a design using AutoCAD) explored using old hydraulic cylinders from earthmoving equipment as the cylinders for a double expansion engine. His Missus objected so the plan never went ahead but welding up a frame to support the cylinders and provide a bed out of RHS would be very achievable without buying castings.

      Phil B