Chevy V8 Scale Engine Plane

Discussion in 'Plans' started by TrashCo, Jan 23, 2014.

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  1. Aug 19, 2019 #121

    davidyat

    davidyat

    davidyat

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    Retailer,
    You make a good point about removing material at the mill and then over to the lathe. What scares me are those squared off, interrupted cuts. In my short learning experience, no matter what cutting tool I use, narrow or wide, there is more chance of the tool grabbing that square end and twisting the part. It takes much longer doing the turning without removing material, but I have the time now that I'm retired and I seem to have a lot less problems.
    Grasshopper
     
  2. Aug 19, 2019 #122

    editor123

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    You need to make a series of tube stiffeners that can be clamped on the bar stock diameter. Use worm gear hose clamps to hold the stiffeners on the workpiece if you cannot weld tabs on the tube for clamping screws. The tab approach is better and stiffer. You should also mill out most of the metal before you put it on the lathe. A great time saver and you don't end up making interrupted cuts.
    upload_2019-8-19_7-31-4.png upload_2019-8-19_7-31-30.png
    Pictures from Issue # 30 of an article in Model Engine Builder on making multi-plane crankshafts. Note the special cutting tool.

    upload_2019-8-19_7-26-55.png Setup for milling out throws before using a lathe to finish them.
    upload_2019-8-19_7-32-54.png
     

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  3. Aug 19, 2019 #123

    SailplaneDriver

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    What do you mean by "biscuits"? Are they spacers to minimize the flex when you crank the tailstock in?
     
  4. Aug 19, 2019 #124

    SailplaneDriver

    SailplaneDriver

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    I did mill away excess but only for the journal I was working on. That way the stock from the driven end was solid and would not flex. It is more time consuming since you have to remove the stock from the lathe and take it to the mill, tram it in and mill it.
     
  5. Aug 19, 2019 #125

    SailplaneDriver

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    editor123, I like your idea of stiffeners. I thought of something similar using worm gear clamps and sheet stock but a tube would be much better. It also means I can mill all the journals at once since the stiffeners will provide the necessary support. Welding or soldering on the outside looks time consuming. I'll try the worm hose clamps first since they would be faster.
     
    Last edited: Aug 20, 2019
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  6. Aug 20, 2019 #126

    SailplaneDriver

    SailplaneDriver

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    I bought a 30" length of 1" schedule 40 pipe and a 10 pack of worm hose clamps. The pipe has an internal diameter of 1.049. I had to cut about a .200 slit at the weld to be able to get it to close down to a bit below 1". I made three lengths: 2, 3 and 4". Hopefully those will be enough. I managed to squash the 2 and 3" down to where they will grip the 1" OD of the crank by squeezing them in the three-jaw so they would be reasonably symmetrical. I don't have enough leverage to do that to the 4" so I resorted to a thick piece of paper. Looks like it will work. I'll try it tomorrow on the almost straightend bent piece to see how they work.

    IMG_20190819_170310.jpg

    I screwed up the threads on three of the clamps by overtightening them; they don't have enough strength to compress the pipe unless you deform the pipe somewhat first. I put some scrap underneath them to allow them to still work on an undamaged portion of thread.
     
    Last edited: Aug 20, 2019
  7. Aug 20, 2019 #127

    davidyat

    davidyat

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    What do you mean by "biscuits"? Are they spacers to minimize the flex when you crank the tailstock in?

    That's exactly what I mean by "biscuits". Spacers made to fit into the web you just made for the rod journal. Mill a piece of scrap, work to get it to fit snugly with hand pressure into the rod journal space and when you move your live center into your offset jig at the tail stock, a small bit of pressure will lock in the "biscuit" and you then lock the tail stock.
    Grasshopper
     
  8. Aug 20, 2019 #128

    davidyat

    davidyat

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    20180621_065402.jpg 20180621_084834.jpg

    Found the images I was looking for. Crank (when I was working on the mains) with the biscuits installed and the crank. Pressure from the tailstock usually keeps the biscuits steady.
    Grasshopper
     
  9. Aug 23, 2019 #129

    SailplaneDriver

    SailplaneDriver

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    Broke the crank in two this time. I had so much stickout of the parting tool that it was just slightly above center height, best guess around .020. Worked fine until I got to a finished diameter of around .300 where it grabbed and twisted the end off. I need to either reduce the stickout or cut a chipbreaker into the parting tool to reduce height. If I am having this much trouble with aluminum, I hate to think what will happen when I go to steel. I'll practice some more with the aluminum remains to see if I can get better at this.
     
  10. Aug 23, 2019 #130

    davidyat

    davidyat

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    Don't know if this could work for you. Build up a crankshaft. I did it on a 2 cylinder, 1 rod throw with 2 rods and it worked just fine. Let's see if I can cut and paste some photos. I just drilled 2, one half inch holes (reamed) 1/2 inch off each center into the rectangular pieces. Pushed the 2 rods through that way everything stays in line. Silver soldered (with 53% silver solder, very expensive but worth it) everything together, then just machined it out. Ended up with only 0.006 thou run out at the ends. After installation with ball bearings at each end, it turns like butter.
    Grasshopper
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  11. Aug 24, 2019 #131

    retailer

    retailer

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    I made up an offset machining holder for my crank - have a look at this post https://www.homemodelenginemachinist.com/threads/first-ic-engine-design-and-build.31266/ and the second page shows how it was used, it allowed me to do all of the machining right up next to the holder or chuck.
    While it did not work 100% how I had intended it to it was a reasonable sucess, the main downside was lateral play of the crank in the holder, while I couldn't feel any play it turned out that I was able to detect the play with a DTI as the grub screws were tightened down and the bigend journals ended varying in size by a few thou, not a disaster but also not made to the design size. I found it was better to move the cutting tool at a steady pace from side to side while at the same time feeding it in only a few thou at a time.

    If I ever make another multi cylinder crank I'll look at making a set of vee clamps machined up from angle iron - a length of vee stock clamped with exhaust type c lamps to each side of the crank I envisage that the vee clamps will need to be custom made in pairs of varying lengths so they can be clamped one each side with exhaust style c clamps. If you ignore the bad perspespective of the pic I quickly drew you will get the idea.

    Just a thought on the material you are practising on maybe aluminium while it is soft does tend to gall up on the cutting edge of a tool and in addition possibly is just not strong enough and you might do better with an easy machining type of mild steel. I made my crank from an unknown grade of steel described by the seller as either 4140 or similar to it.
     

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  12. Aug 25, 2019 #132

    SailplaneDriver

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    davidyat, I'm not sure your method for a built-up crank would be practical for a multi-plane crank. Steve's drawings have an option for a built-up crank and it looks more difficult to build without runout.

    retailer, I like your offset holder. I tried making a clamping offset holder with a recessed square for indexing. I turned it with a 1.00 spigot so it coud be used in a 1" collet. It doesn't work well in practice. Probably needs some refinement.

    IMG_20190824_165312.jpg IMG_20190824_165320.jpg IMG_20190824_165229.jpg
     
  13. Aug 25, 2019 #133

    johnl

    johnl

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    Try making a practice crank out of 12L14 leaded steel.
     

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