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JoeH

Pedigreed Bulldog
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Posts posted by JoeH

  1. 10 hours ago, terry said:

    Should be stamped on front on that flat spot next to power divider, might have to wire brush it to see it.     terry:MackLogo:

    And a chipping hammer, underside of the truck tends to get caked in concrete. Truck runs just fine for me, I like it's gearing. It'll do 70+ IIRC, though I never take it on roads with speed limits above 55. Biggest problem I have with the truck is it's about a foot longer than any other triaxle in the area. 228" wheelbase, steers a bit like the Titanic.

  2. On 3/21/2019 at 2:37 PM, 41chevy said:

    Tonight is the regular monthly Village Meeting with public participation. I'm looking forward to it. Taking my M917 to the meeting to exercise it a bit and show off my new vinyl sticker on the steer diff. 

     

    pedM920DumpTruck16_zpswzza8gaa-vi.jpgHosted on Fotki

     

    Keep the updates coming, though I know that could be a while the way bureaucracy works.

  3. That's exhaust valve diameter? That has about 1.8-1.9 square inches of surface area, so that's about 40 pounds of pressure. At higher RPMs you need more pounds of spring tension because the valves have less time to close between cycles. 40 # of pressure on the valve leaves you 150# of spring pressure. Of course the back pressure doesn't push on the valve with that 40# until the valve is shut. At fully opened the valve spring might not have much resistance, as the pressure is vented into the cylinder. But, you also have vacuum created on the intake stroke which is acting to pull the exhaust valve open, which is takes from your remaining 150# spring pressure.

  4. I got the 60 pounds of pressure because it's 20 pounds per square inch and a 2 inch valve has 3.14159 square inches of surface area. If it's a 3 inch valve the surface area jumps to 7 inches, which jumps to 140 pounds of back pressure acting on your valves, leaving only 50 pounds of spring pressure shutting the valves.

  5. You have to take the 190# and convert it to psi on the surface area of the valve head. If it's a 2 inch diameter, πr^2 is 3.14159. Now take your 20 psi back pressure and you have 60+ pounds of pressure trying to open your valves, which leaves 130 pounds of spring pressure holding them shut.

  6. I think the butterfly brakes are operated by an air cylinder. I assume you can put an air regulator on it to control the amount of back pressure the brake generates.

    Find out what # springs the exhaust valves are, and what diameter they are. Run a little math, you'd have to generate enough force to counteract the valve springs to cause valves to float. You'll need to leave a safety factor to ensure the springs can still hold the valves with some force. 

    Your other choice is a traditional Jake brake that opens the exhaust valves at TDC of compression stroke to dump off the combustion energy. Doesn't generate any back pressure, and certainly doesn't take 700# off your payload.

  7. If they're double frame trucks, the best thing you can do to preserve them is split the frames apart one side at a time and sandblast/paint them. Some people even drill and tap the outer frame rail for grease fittings so they can prevent future rust jacking. Nowadays they make a "heavy single" frame, I wish they had started using them sooner. 

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