Notes on Using Epoxy Primer

Never used this stuff, but the information is worth filing away for when the day comes.

Note that epoxy primer seems to be a great way to prevent rust on bare metal, something regular primer does not do (and I can confirm that).

Mostly an original quote, but with a little reformatting to make it easier to read.

From: Radkins from the Home Shop Machinist forum, here.

Epoxy primer is great stuff and the first thing I do to any body panel or repair is to spray it with epoxy primer, the stuff is expensive but it can't be beat for corrosion protection!

A couple of tips for using this type of primer:

  1. It needs a rather rough surface to adhere properly. I scuff the bare metal with 180 grit paper and then apply two coats allowing it to become dry to touch before applying the second coat. If a finish is not applied within a day or so, this varies with brands, it will need to be scuffed with sandpaper and another coat applied before any topcoating is applied including conventional primers.
  2. If left for any length of time then it should be topcoated with another primer such as lacquer or one of the polyester filler primers. No scuffing needed if coated within a couple of hours. If left for weeks, never mind years, it becomes EXTREMELY hard making it very difficult to sand and causes difficulty in getting topcoats to adhere. If something like even simple lacquer primer is applied around two hours after the original application it will adhere quite well and is then easily prepped for painting even after being left for long periods of time, old uncoated epoxy primer however is a absolute nightmare to properly prep for finish painting!

Oh, and he follows up with this:  (something else I learned today).

NO, DO NOT SANDBLAST BODY SHEETMETAL!!!!! A sandblaster will warp most sheetmetal body parts beyond any hope of repair! I don't mean "Aw s#!* now I am going to have to fix that", I mean toss it in the scrap and buy new parts kind of ruined. Some parts that are stiff and well supported like door posts and some firewalls may be blasted ok but fenders, hoods, trunk lids, etc will be instantly distorted way beyond any repair. Those sand particles act like millions of tiny peening hammers and will distort the surface of the metal due to the uneven stretching (and no, heat has absolutely nothing to do with it despite the common misconception so keeping the parts cool is futile!). While it can and has been done successfully the blast operator has to REALLY know his stuff and even then it's highly risky.


Turning a Radius

A neat way to mill a radius on something with a through hole.  Just put a pin in the hole, rest the pin on the top of the vice jaw, and then rotate, clamp, and cut repeatedly.


Enduro Computer Project

WAIT!  Before you start reading and get disappointed, this is my research blog.  At this point, there is no enduro computer, it's not finished.  If fact, I'm still roughing out the design.  It may never get finished.  And, it's low priority for me.  I'm starting this now because I'm having to work through some technical issues and maybe somebody else might find my notes useful.  That's all.

Current status: Pre-Alpha, just planning at this point.

The plan: To set up a 2.4" TFT LCD display shield on an Arduino Uno with a Hall Effect sensor and some code and mount it on the handlebar of my Dirtbike for enduro racing.  Total cost should be in the $20 range (and that's probably overestimating).

So, I picked up a 2.4" TFT-LCD touch-screen from Ebay.  Absurdly cheap, in the $5 range.  It's an Arduino shield for an Uno, and it leaves enough pins for me to run a hall effect sensor, which I'll just salvage from a bicycle speedo (another stupid-cheap Ebay purchase).

Problem 1: Drivers for the TFT-LCD.  It appears there are a great many variants of these shields available, and very few come with any kind of documentation or libraries.  Most happen to have "www.mcufriend.com" printed on the PCB, so that means very little.  That website is in Chinese.

Most of the available drivers I tried for this just left a white screen, though the serial output seemed to work.  I did find one, SWTFT, that mostly works.  I can run the tftpaint example, except there is a white bar down the side.  Running the graphicstest example show that it is trying to write under that white bar, and it is trying to write with a backwards font.

Solution 1: The key is to identify which control chip you have and then get matching drivers.  Identify your chip with a utility found here.  Open the Serial Monitor in the Arduino IDE to see the information.

Solution 1a: My TFT-LCD shield uses the '4535' chip.  I found libraries for it at:  Cee'z Blog.  If you use his libraries then buy him a cup of Coffee, I did.  It's worth it.  Everything worked great with Cee'z libraries and example sketches, except the touchscreen was backwards.  No problem though... just run his example calibration sketch and copy the resulting numbers into the config section of the sketch you want to run.  Yes, the "min's" end up being bigger than the "max's" but everything's good after that.

The 'calculator' utility makes for a great example to work from.  Next thing is to figure out how I want the main display to look, and maybe a few sub-displays.

Problem 2:  Using the shield on an Arduino Uno seems to use all the pins.  I've read that A2 is not used, but my shield has a label for that pin (LCD_RS) and not using that pin (bending it out of the way... hey, it's a $5 shield) leaves a white screen.  The Ebay seller states that "you can use digital pins 2, 3 and analog 4 and 5. Pin 12 is available if not using the micro." Some of those pins are labelled. It will not work with D2 and D3 bent out of contact, so the seller's information is not correct either.

Solution 2: The D0/D1 (RX/TX) pins are not labelled on the shield, bending them out of the way left the display still working fine, along with the touch screen, but I've not yet determined if they're needed for the SDcard.  A5 (not labelled) does not seem to be used either.  A4 is labelled as the LCD_RST (reset?) and while it will work bent out of the way, I'm not sure if the library is writing to it or not.  Of course, switching to a MEGA, instead of an Uno, gives a lot of useful pins... but also left a white screen.

Solution 2a:  Using the MEGA is actually fairly simple.  Just edit LGDP4535.cpp (in Cee'z library), commenting out the Uno line and uncommenting the MEGA line.  '//' means this is a comment.
This says to use a MEGA instead:
#include "mega_24_shield.h"
//#include "uno_24_shield.h"
Don't forget to switch back if you want to use an Uno.

Background:  Enduros, for those that don't know, are races where the object is to travel at a set average speed rather than as fast as you can.  The trick to winning them is, however, not just riding at that speed but rather as fast as you can at the start of a section, then guessing how far to the next check, and then calculating what time it should be when you get there.  Parts of the section are typically very difficult to maintain the correct speed while other parts are easy.  Thus, there is a lot of guesswork involved, and math at the same time.  It's pretty easy to figure out how far you should have gone in 15 minutes if the speed is 20km/h:  20km/h * 1/4h = 5km.  Figuring that out for a speed of 17km/h over 10 minutes: 17km * 1/6h... not so easy when you're crashing through the bush and scrabbling over rocks and roots at speed.  Yeah, people actually pay to do that.  Crazy people anyway.  Even crazier ones pay big money for a handlebar mounted computer to do the math for them.  Then, there's cheap and crazy people like me that set out to build their own.

The Interface:  There are a lot of different ways to present the needed information but what I think I want for the main display is simply +/-Minutes, as big as I can make them.  Negative minutes means I'm ahead of where I should be and have some slack.  Positive minutes means I need to run WFO and catch up.  It will have 2 on-screen buttons:  Error and Check.  'Error' means I've missed a turn, happens a lot in enduros, and need to subtract some distance while I get back to the marked trail.  'Check' marks the clock, displays my results, resets the minutes without resetting the seconds, and lets me set the speed for the next section.

More later...


Turning the End of a Big Bar

Say you need to turn the end of a bar that is too big to go through the lathe headstock and too long to fit between centers (or the center-rest if you have one)...

Here are some answers:

Arcane suggests:  If you have a milling vise setup that attaches to the cross slide for your lathe and a boring head with a MT3 taper, clamp the shaft in the vise, center it on the spindle and then use the boring head to reduce the end.

Dan suggests:  There was someone who did an interesting trick. They welded a smaller piece to the end and chucked it up. Supported the far end in a steady rest. Then they turned down the original bar and parted it. Rotate and repeat.

Better yet, just start with stock longer than required an part off the chucked bit.

My idea, specific to my 3in1 machine:
Using something of suitable height, like the angle table (level, just for the height), make a vertical clamp that hangs outboard the lathe.  Swing the head over to match and lock down, then use the X/Y to center.  Once centered, use the boring head as above, with the cutter pointing inward.  This would give me about 4' of length, and it would be easier to set up than removing the tailstock to use the lathe spindle.


Making SS Springs

Interesting post on HSM by Dorn:

Using annealed stainless steel wire (aka safety wire) that is not springy in this state, it can be work-hardened by stretching.  Once work-hardened, it can be wound into a spring.

Rich added:

I also use a "Drawing" technique when I want smaller wire for a model or repair application.  I open my vise about 4 or 5 inches and then wrap the wire around the jaws ( 2-3 wraps ).  Now I open the jaws more and draw the wire down to a smaller size with out having the use my legs or arms, only the vise leadscrew.

Never tried it... but it's something to keep in mind for when that someday comes along.


My Linux for Kids Notes

This is not a "how to" guide, a definitive list, nor even a recommendation for what to do for your kid. It's simply my notes. I needed to keep them somewhere, I needed a place where I could update them easily, and I wanted it "in the cloud" so I could always find it. Oddly enough, a blog is actually a good place to do this. I don't mind sharing my notes and if you find them useful... good for you. If you have some other recommendations, feel free to comment.

I'll be updating this as I go...

The list of linux apps I install, suitable for cut and paste into a sudo apt-get install command for a debian-based linux distro, because that's how I do it:

sudo apt-get install gcompris tuxpaint tuxpaint-config tuxmath tuxtype ktuberling stopmotion playonlinux extremetuxracer neverputt pingus funnyboat pysiogame stellarium stellarium-data supertuxkart sugar connectagram

Via playonlinux, install:
  1. 3d train studio - downloads free version via script. Pretty awesome for kids that like trains.
    - 20 trains (running) is a fun one to download. 
What each app is:
  1. gcompris - a big bundle of kids games, puzzles, and educational activities. Highly recommended. 
  2. tuxpaint - awesome painting program with lots of stamps. The config allows various settings. 
  3. tuxmath - still seeing if my kid likes it. 
  4. tuxtype - my kid loves this typing tutor, from about 1yr old. Seriously. 
  5. ktuberling - Mr Potato Head goes cyberspace. 
  6. stopmotion - makes stopmotion - still testing this one 
  7. playonlinux - scripts to install many Windows apps under wine. Most, but not all, require the CD 
  8. extremetuxtracer - 3D racing game, with Tux sliding down a ski slope. 
  9. neverputt - a minigolf game 
  10. pingus - a funny game for kids that like penguins, and what kid doesn't? 
  11. funnyboat - great kids game. 
  12. pysiogame - another educational game suite like gcompris, slightly more advanced. 
  13. stellarium - study the planets and stars. 
  14. supertuxkart - 3D racing game in go-karts. 
  15. sugar - the One Laptop Per Child OS.  Still experimenting.
  16. connectagram - word de-scramble game.

Other stuff to remember:
* Celestia - no current install candidate.


Flexture Clamps

Idea from a Dan Gelbart video (Building Prototypes, part 13):

If you want to clamp something, cut a slot near it, then drill in the middle of the slot, then tap the hole for a pipe thread.  When threading in a plug, the taper will expand the slot, which will move the metal to clamp the part.