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About purepmd

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  • Scale I Build 1/25th, 1/24th

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  • Location Gering, Nebraska
  • Full Name Mark Botzki

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purepmd's Activity

  1. purepmd added a post in a topic Let's Talk Diesels..   

    It makes you wonder, that, if in the name of weight savings, the engineers are using theory and not practical evidence when it comes to designing the reinforcement of the main journals and caps. Maybe even in the crank itself. For the lack of a few pounds of well placed cast iron and steel, you get ridiculous failure rates. I would almost bet real money, the thrust bearing main journal is flexing and or cap is walking during clutch disengagement and under high load situations. That is one thing to be said for the heavy 3406 family. The bottom ends of those engines were almost bullet proof, as long as you keep fresh oil in it like you were supposed to. Cat had more million mile, in-frame free engines than anyone else. I am sure a lot of mechanics as well as drivers miss the yellow motors under the hoods. Just my 2 cents worth.
    Happy Thanksgiving Everyone.
  2. purepmd added a post in a topic Let's Talk Diesels..   

    Hey Michael,
    Fishing for Gearheads, throwing bait like that in the water.
    K.J. is right. Rudolph Diesel, in the mid 1890s, worked on using the inherent heat from compressing air, to ignite a fuel. After a few experiments, one explosion that almost killed him, he found a by-product of the crude oil refining process. It was cheap, plentiful, and at the time burned off as waste. He found that by atomizing, and injecting this waxy fluid into a piston compressed cylinder, as the piston neared Top Dead Center, the fuel would combust, and the engine would sustain itself, without external ignition source.
    Clessie Cummins work on 4 stroke engines, in the 1930s, and turbochargers, in the 1950s, were huge coffin nails for the 2 stroke Detroits. He used the Indy 500 as his final test bed, having been on the Marmon pit crew for the first 500 in 1911, setting speed records, endurance records through the 1950s, all with diesels.
    California hot rodder Clayton, speaks the truth. Hot rodders, after WWII, started pulling the superchargers off of diesels and adapting then to automotive gas burners. Even today, the size designations of Roots type, (GMC), blowers. 4-71, 6-,8-,10-, 12-, 14-71 all owe the name to the old Detroit engine displacements. The size of the supercharger was determined by case and rotor size needed to fill the given number of cylinders, 6, 8, 12, etc with 71 cubic inches of air per crank rotation.
    Incidentally, the 2 stroke Detroit engines require air to be forced into them by the 'blower', in order to run at all. Being a 2 stroke design, with the intake ports in the cylinder walls themselves, they do not have a separate intake stroke, like 4 stroke, gas and diesel engines use to draw in their own air.
    The most prevalent configuration, today, is the inline 6 cylinder. Early on, Cummins found out that inline engines generate more torque per cubic inch than VEE configuration engines. With a couple of notable exceptions, the V903 Cummins, and the 3408  Caterpillar, the majority of successful Truck engines are 6 poppers. The first, production engine to make 600 horsepower, was a Cummins KTA-600, a 6 cylinder. A benchmark not even the venerable 12V-71 could make.
    As I try to get my inner Diesel Geek under Control, don't forget, even ALLIS - CHALMERS tried to get into the truck engine market, in the 1970s. "Big Al", as it was marketed as, looked good on paper, and even painted purple metallic, but in reality had severe crank longevity issues that made it just another also ran.
    Now, consider all the different developmental series for each mark. The Detroit V-71s, V-92s, V-92 Silver, Series 60, DD 14 and DD15 versions. Cat,s 1693, 3406A, B, C, 3406E, 3408, C-15, C-16. Cummins' NTC series, KTAs, 855 series, ISX, Signature 600, just name a few.
    OK, I'll stop now.
  3. purepmd added a post in a topic Peterbilt Devil's Cut Whiskey Hauler   

    Pretty slick! Great build quality! Going to follow this one, closely. Very cool.
  4. purepmd added a post in a topic White 7400 & Detroit 6V71 project   

    Sean, really looking good. Your six pot Detroit looks way cool. This project is off to a great start. Looking forward to updates.
  5. purepmd added a post in a topic Why a Cab Over?   

    Clayton and KJ hit the nail on the head. Back in the 1960s, a class 8, on highway truck could only be a maximum of 57' and weigh 72,800 lbs. The easiest way to get the most payload within these regulations, was to put the driver over top of the engine, and keep the wheelbases under 190 inches. The cabover ruled the road, especially when you factor in all the restrictive bridge laws that could, and would be enforced. Each state setting something different.
    Look at the AMT truck and trailers were all modeled off equipment of the day, 40 footers, and short wheelbase cabovers.
    l did the math, and it was 33 years ago, I drove my first truck. It was a red and white, white freightliner FLA. Catpowered and 15 speed equipped.  
    One of the best things about cabovers is the visibility. You are not looking around a hood, or exhaust, or sleepers. You are right overtop of the left steer tire, inline with the side of the trailer. Backing up was never easier. Blindsiding was a bit tougher, though.
    Clayton, you tastes and mine run along the same lines. Freightliner FLA, Pete 352, 362, and Kenworth K100 are my favorites. With honorable mentions going to the CL9000, IH9670, Road Commander II, Astro 95, and  IH 4070B.
    There ain't no feelin' like Cabover mobilin'.
  6. purepmd added a post in a topic Shifting Gears..   

    ^^Preach, Brother, Preach.
    If it weren't for the Federal D.O.T., Creeper Cops, Steering Wheel Holders, and ignorant 4 wheelers, it would be the perfect job. 
    I am all teary eyed and nostalgic now, myself. Lol.
  7. purepmd added a post in a topic Shifting Gears..   

    Yes, Michael, very similar effect, only you use the throttle to break the torque lock in the transmission instead of letting gravity do it for you.
    Hey Clayton, you, obviously know what I am talking about. And know it well. It is a great feeling when you row through the gears, hitting each one just right. Did I mention I HATE class 8 trucks with automatics. It is a well practiced, well executed skill set that is dying at an alarming rate. 
    If you notice in the video, the driver's left leg never moves after he gets rolling. Not even when he splits gears, or changes ranges. You can tell, he LIKES driving that truck, and showing off a bit.
  8. purepmd added a post in a topic Shifting Gears..   

    Hey Michael,
    When I first started driving, Over 20 years ago now, it was explained to me in these very words:
    "The clutch is for starting and stopping, ONLY." Spend any amount of time with the same truck, and you learn its peticular traits. You learn how to shift to neutral just by lifting your foot off the throttle. Then, hopefully, you learn how to shift it into the next gear, up or down, just by engine RPM only. Down shift and you raise the engine speed with the throttle, up shift and you wait for the engine speed falls to the normal gear step. The gear step being the difference in engine speed, at the same road speed, (MPH). For example, if at 50 MPH, in 12th gear, and the tach says 1100, drop to 11th gear and the tach would read 1600 RPM. This varies with every different transmission. An 18 speed may only have a 250 step when you split each gear, 1-2, 3-4, etc. While a 9 speed will drop, say 500 RPM, having only half the available forward gears. A car, with a manual transmission does the same thing, just with a bigger swing of the tach needle. 
    Floating the gears, basically, is shifting, up or down using only your right arm and right foot. No clutch. With practice, the shift lever, almost 'floats' into the desired position. No grinding, nashing, or missed gears. It will literally shift with surprising little effort. The alternative, is 'Jamming' it into gear. Yes, the term Gear Jammer, long before my time, was a derogatory term.
    Clear as mud?
  9. purepmd added a post in a topic Movin On Kenworth color.   

    Angel, if you have an air brush, I have the exact colors, mixed by Scale Finishes. A 2 oz bottle of Kenworth Ivy Bronze, metallic, and 1 oz bottles of Kenworth Lime and White. I was going to build a 1/16th VIT, but it is so far down the list of projects, I would let them go, if you what them. All 3 are premixed, brand new, and unopened. P.M. Me if you are interested. Reasonably priced as well.
  10. purepmd added a post in a topic Revell w series kw's   

    Hey Sam,
    They pretty much are. All have the extended hood, and 3408 Cat in them. About the only real difference is the color they are moulded in.
  11. purepmd added a post in a topic Scratchbuilt Timpte Super Hopper   

    KJ, beautiful, beautiful work! You can almost see the grain dust flying off the auger now. Truely inspirational.
  12. purepmd added a post in a topic 1st Annual, Big Rig Build Off, 2017 Calender build contest.   

    Really Great to see this up and running! I have to make sure "Plan A" is possible, before my cat and bag part ways. Do have some good "Plan Bs", though.

    First Plan B...Ford CL9000:
    Second Plan B...International 9670:
    Third Plan B...Kenworth W900L with either a 3406E or Signature 600:

  13. purepmd added a post in a topic AMT Peterbilt 359 California Hauler Wrecker   

    You say 'liberties', I say enhancements! Far outshines the box art while retaining all of the appeal, Outstanding work.
  14. purepmd added a post in a topic Post your "Snap" kits.   

    JT, imagination and execution perfectly paired. Really liking the KW / Ford combination, very original.

    Landon, your all black Pete istantly made me think of that show truck, Project 350, nice work. The black, white and red Pete stopped me in my tracks, great color choice.
  15. purepmd added a post in a topic all White - Autocar here   

    Hey Mark, thanks for the kind words. They are decals, my hands are not that steady anymore, They were the ones that fit the best off of the Can-Do wrecker decal sheet. One of the ones I have yellowed, badly, completely unsuitable for most colors. I figured, some real close trimming, and over black, they might work.