Announcement

Collapse
No announcement yet.

Davenport Diesel-Mechanical Locomotive

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Davenport Diesel-Mechanical Locomotive

    Okay, since the board has been relatively quiet I'll show some pictures of my humble project. This is actually my "practice" locomotive; the main event is a 1.5" scale mikado. I figure that if mistakes are to be made, I'll make as many as possible on this. So far I've been pretty successful!

    The original was a 12-ton 3' gauge locomotive built in the 1930's for a sugar cane plantation in Louisiana. As you can tell from the photos, it was very strongly influenced by steam locomotive construction practices, with equalized axles and a lead truck. (Note that Davenport called it a 2-4-0.) It also sported a bell and a whistle!

    My version will be battery-powered, 7.5" gauge, 2.5" scale. The frame is flame-cut from 1" plate (the original had 5" thick frames!). The coupler pockets are cast in aluminum using a lost-foam method in my "driveway" foundry. The wheels are turned from 1" steel plate. So far, the only commercial parts are the bearings, chain, sprockets, and fasteners. Currently I'm working on the pony truck, which will use heart-shaped rockers.

    Dan Watson
    Attached Files
    Last edited by fender; 02-26-2008, 03:12 AM.

  • #2
    Originally posted by fender View Post
    Okay, since the board has been relatively quiet I'll show some pictures of my humble project. This is actually my "practice" locomotive; the main event is a 1.5" scale mikado. I figure that if mistakes are to be made, I'll make as many as possible on this. So far I've been pretty successful!

    The original was a 12-ton 3' gauge locomotive built in the 1930's for a sugar cane plantation in Louisiana. As you can tell from the photos, it was very strongly influenced by steam locomotive construction practices, with equalized axles and a lead truck. (Note that Davenport called it a 2-4-0.) It also sported a bell and a whistle!

    My version will be battery-powered, 7.5" gauge, 2.5" scale. The frame is flame-cut from 1" plate (the original had 5" thick frames!). The coupler pockets are cast in aluminum using a lost-foam method in my "driveway" foundry. The wheels are turned from 1" steel plate. So far, the only commercial parts are the bearings, chain, sprockets, and fasteners. Currently I'm working on the pony truck, which will use heart-shaped rockers.

    Dan Watson

    Thanks for sharing, that looks like one well built locomotive in the making. please keep up the flow of information on progress.
    Last edited by mdainsd; 02-27-2008, 02:52 AM.

    Comment


    • #3
      Yes, thanks for sharing. I have a soft spot in my heart (head?) for critters and will enjoy watching this project.

      Greg B.
      Mechanical Engineers build weapons. Civil Engineers build Targets....When the guy at the door said, "Alcohol, Tobacco and Firearms," I naturally assumed it was a delivery! The first lie voids all dialog. "From my cold dead hand!" C. Heston

      Comment


      • #4
        Hey Dan

        You must be slipping...

        You are supposed to DRINK the beer, not photograph it.

        At least it's good beer.....
        Bill Shields
        Living proof that just about anybody can build a working loco...

        Comment


        • #5
          Bill,
          That is my standard reference item for scale. Everybody knows how big a can of beer is, right? Or does it not translate to land of Oz?
          Dan

          Comment


          • #6
            Size Matters

            OBVIOUSLY...

            you have never been subject to the 'bet you cannot drink a 6 pack of.." with the Foster's liter cans....
            Bill Shields
            Living proof that just about anybody can build a working loco...

            Comment


            • #7
              I am curious on how you plan on driving the wheels from the engine/transmision? I expected to see one more sproket on an axle. What's your plan?

              Tom C.
              tom_at_srclry_com
              Lost somewhere in Michigan!

              Comment


              • #8
                Tom,
                That was my original plan, but someone suggested that the main drive chain could go around three sprockets, (the third smaller sprocket will be on a jackshaft) which eliminates an extra chain from the drive. I'll post a rough sketch tonight.
                Dan

                Comment


                • #9
                  Hey Dan that little Davenport will be a nice one. Lookin good.

                  One thing to keep in mind about sprocket layouts is you need as much wrap of the chain around each sprocket as possible. 180 degrees is great. 90 degrees is about minimum. If you have to add idler sprockets to get better wrap on the driver and driven ones, to drive a chain between two shafts as you show in the pix, be sure to put the idler on the slack side of the idler or the idler bearing will wear fast.

                  Comment


                  • #10
                    Tom,

                    Here's a crude sketch of the drive design. By looping the main drive chain around a smaller sprocket on the jackshaft, I can eliminate the extra sprocket on one of the axles and an extra chain, as well as provide a means of tensioning the chain. I want to avoid having the lower chain "droop" and possibly catch on the rails of turnouts or crossings (or drag in the dirt!).

                    I'll probably have to experiment with different size sprockets on the motor shaft to get the speed I want from the loco. This supposed to be a switcher/hauler, not an express loco. Top speed per Davenport specs was 13.6 m.p.h.!

                    Dan
                    Attached Files

                    Comment


                    • #11
                      Dan,

                      Just Calculate for your design (sample only provided):

                      You'll likely want to have top end at max of 2.5 MPH real speed. (I know a faster scale speed than your prototype - but you have to make some adjustments).

                      Thats (about) 5289 * 2.5 / 60 *12 = 2640 inches per min.
                      with 5" wheels thats' (about) 2640 / 15.7 = 168 RPM max axle RPM.

                      If the axle sprockets are 36 teeth: 168 x 36 = 6048 RPM
                      If the small jack shaft sprocket is 9 teeth: 6048 / 9 = 672 RPM
                      If the large jack shaft sprocket is 36 teeth: 672 x 36 = 24,192 RPM
                      If the motor sprocket is 9 teeth: 24,192/ 9 = 2,788 RPM of motor

                      Electric field wound and perm mag DC motors are avialable in the 2200 - 2800 RPM ranges - so you're good to go.

                      40 and 41 chains can have 36 and 9 sprockets easily found.

                      You can choose your motor, chain size and avialable sprockets selection to back into the needed parts. (You can also control motor speed electrically to reduce the max RPM - but you'll want it to be close the motor design for power efficiency.

                      Been there and done it. Work the calculations then do the physical mounting design with the selection of components. You have the room to develop what you need - I didn't, and had to reduce motor torque and speed with use of electronic controls. Electronic speed reduction will drive amperage draw up and reduce time between charges, so design for close to motor speed.

                      See my: http://www.coslar.us/FA1.html
                      Last edited by emccamey; 02-28-2008, 02:05 AM. Reason: mis-type - spelling
                      -ed mccamey-
                      www.coslar.us
                      www.facebook.com/ed.mccamey
                      COSLAR RR
                      SWLS Member

                      Comment


                      • #12
                        Actual Speed

                        Shouldn't you set-up your drive system to run about 10 MPH wide open? With a 10 MPH maximum you can maintain 7 MPH without running wide open. Seven MPH is the speed limit on the SVLSRM and you should be able to maintain that speed to keep up with traffic on the main line. It is only common courtesy not to be a rolling road block on the main line. Bill

                        Comment


                        • #13
                          Bill,

                          About 7 MPH would be my assumption for a main road locomotive. But Dave is designing and providing a yard locomotive. And one very large hunk of metal the frames appear to be. If Dave intends to operate the Davenport out on the main - then getting closer to 7-8 MPH capability would be advised and get the axle RPM up to about 500 to 575 RPM would work out well.

                          Being an aside though, I'd find that 7 MPH for a 7-1/2" gage track as a 'normative' is too fast anyway. My FA1 could actually clock in at about 13 MPH - but I'll tell you this, I DIDN'T like going that speed at all, and have reduced it to no more than 8 MPH with a top end variable resistor speed control in the controller.

                          Track speed is as much a function of the track condition and the avialable geography and geometry of visibility and distance. Some tracks can handle and allow for 8-10 MPH with out a problem, and some - 5 MPH is way too fast.

                          You do need additional 'power' for longer grades and for longer trains, which when running light can allow for faster speed.

                          It's all a 'design' and 'purpose' choice. I've been behind one of those Cli-Shay bottle necks and yes, it's sometimes a frustration, but it was moving a lot faster than a scaled speed of it's prototype.
                          -ed mccamey-
                          www.coslar.us
                          www.facebook.com/ed.mccamey
                          COSLAR RR
                          SWLS Member

                          Comment


                          • #14
                            Yard Locomotive?

                            He may be building a yard loco but I feel sure it will not stay in the yard, it will end up on the main. At 2.5 MPH maximum speed it will be a rolling roadblock and cause much consternation among the other engineers. You mention being caught behind a Clishay. Isn't the Clishay designed for use in the woods like the regular Shay? Don't quote me but wasn't the Shay designed with a maximum sustainable speed of 10-12 MPH? 12 MPH divided by 8 = 1.5 MPH as scale speed. The Shays that Ken Schroeder supplies casting/prints for will run with most rod engines so they are running well above "scale speed". As a concession to the other engineers we must design/build our locomotives with the capability to run at normal track speed.
                            Bill

                            Comment


                            • #15
                              Thanks for everyone's comments. On the matter of speed and motor, I have a permanent magnet motor I bought on ebone so at this point I'll have to experiment with various sprocket sizes to get a reasonable speed. I was joking about the top speed of the prototype, for to scale that exactly would be a bit slow. I've even thought about making the motor mounting adjustable so that I could quickly change out the motor drive sprocket according to track conditions, higher gear ratio for hilly track, lower ratio for more level track. (Also, higher ratio for beginners and kids!)

                              I'm interested in Watt's comment about the "wrap" of the chain around sprockets.....maybe I should revise the design so that the smaller sprocket is above the chain instead of below it. That would give more "wrap" of the chain without introducing idler sprockets ???

                              Dan

                              Comment

                              Working...
                              X