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Home Model Engine Machinist > Showing Them > A Work In Progress > Rockerblock I.C.--Something a little different-

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Old 04-16-2017, 10:36 PM   #41
Brian Rupnow
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So, here we go again, making it up as I go along. What are you looking at?--Well, I don't have any 5/16" plate, but I do have some 2" x 3/8" steel flatbar. First job was to mill a length of it long enough to make 2 crankshaft webs down to 5/16" thick. Next step was to lay out the profile on one end of the milled down section. Then cut that end off, clamp it tightly to the remaining piece, and run a bead of weld on both sides about half an inch long. This ensures two things. Most importantly, that any holes thru part #1 are going to be dead nuts in line with any holes in part #2. A secondary benefit is that I only have to drill and ream any holes one time. I don't do this in my mill vice, because I don't trust it not to "cock up" a little bit when I tighten the vice. This results in very bad juju on crankshaft webs. I will put a sacrificial piece of plate between this bar and my milling machine bed, and clamp it to the bed for all the drilling and reaming. I will then saw and mill away everything that doesn't look like a crankshaft web, leaving the two welded areas until the very last step before I separate the two pieces. They will be match marked with a center punch so that I don't reverse one or the other when assembling the crankshaft. Crankshafts are one of the things where "Close really does count".


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Old 04-19-2017, 01:29 PM   #42
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The crankshaft webs have been drilled and reamed, then trimmed from the parent stock with the bandsaw. They are still welded together in two places. Next step is back to the mill to square up any "straight-line" surfaces, then mount them on a stub mandrel and turn them to finished diameter in the lathe. I will probably put a bolt and nut through at least one of the "lightening" holes and cinch it up tight so that when the welds get machined away the two pieces of plate won't try and slip and get out of alignment. This wouldn't affect the geometry of the plates in any way, its just that generally bad things happen whenever something tries to "slip" from where you intended it to be when you are machining it.


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Old 04-20-2017, 01:03 AM   #43
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My "Gas demand valve" plans from Jerry Howell came today, along with some very small Tecumseh engine carburetor needle and seats parts and a diaphragm. The detail drawing of the parts I have to make seem to be well done, but it's pretty damned sparse on assembly drawings. In fact, there are no "assembly drawings" as such, just printed instructions that eventually make sense after you have read them and taken all the tiny parts out of the bags and studied on them to see how this thing works. Apparently I now have to buy a propane regulator to use with this thing, and I have no idea what that will cost, but will try to find out tomorrow. I had an email today from the waterjet cutter saying I could pick up my curved spoke flywheels tomorrow, so I'm fair excited about that. I am going nuts right now with design work, to the point where I can't get time to do my own "hobby" stuff.
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Old 04-20-2017, 12:15 PM   #44
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Here is a link someone sent me, with some very good information about the "demand gas valve" that I just purchased.---Brian
http://www.floridaame.org/HowTo2.htm
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Old 04-20-2017, 07:58 PM   #45
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Today we are talking "beautiful things". I went this morning and picked up my waterjet cut flywheels. Man, are they ever nice. These are 3/4" thick mild steel, and the finish on the inside of the cutouts is very, very nice. The man who cut them said he can cut up to 6" mild steel. I will be machining the outside diameter, the 3/8" bore thru the center, and will take a 3/16" deep "face" cut on both sides in the spoke area. I may paint the parts of the flywheel I don't machine. These flywheels are 4 7/8" diameter and have about 1 1/8" diameter inside the cutouts in what will become the hub area. These are the first parts I have had waterjet cut, and although they are pretty, they are not for the faint of wallet. I paid $90 for these two. Fortunately, I got a $100 bonus last week for finishing a "panic" design job ahead of schedule.--that worked out well!!! Laying on my old blue steel handbook you can see my two finished crankshaft webs. If anybody wants the dxf file for these flywheels, email me at brupnow@rogers.com and I will send it to you. I have to give credit to Philip Duclos for the pretty shape of the spokes/cut-out areas. I didn't copy his numbers, but his "How to" article in "The Shop Wisdom of Philip Duclos" was certainly a big help to get me started in the right direction.---Brian
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Old 04-20-2017, 09:16 PM   #46
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I'm going to get bold here, and do something I haven't done before. Since my crankshaft is built up from individual components pressed, Loctited, and possibly pinned together, I'm going to make up a one piece con-rod and assemble it with the crankshaft. If it works, then great, I'm way ahead of the game. If it doesn't, all I've wasted is a bit of time. Since this is a "demonstration" engine and is not going to see long hard hours of use, I'm not going to run any bearings on the con rod. Aluminum rod running on steel crankshaft lasts a long time if it is kept well lubricated.
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Old 04-20-2017, 11:55 PM   #47
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I'm not blazing thru this build like I have some others, but I did manage to get some machining time in today. The con-rod still has to have the center relieved, but at least I did something. I can't assemble the crankshaft until I have the con-rod finished so I thought this had better be a priority.
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Old 04-21-2017, 12:51 AM   #48
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Brian a lot of my old model aircraft engines con rods were aluminum alloy of some type, plain no bearing and they ran for many hours at high rpm with no sign
of wear or failure.I guess caster oil in the fuel is hell of a good lubricant.
What alloy is best for to use without bushing ? I have a bit of 7075 I was thinking of using but not sure.
cheers
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Old 04-21-2017, 11:59 AM   #49
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John--all the aluminum I use is 6061---brian
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Old 04-21-2017, 06:13 PM   #50
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I got so tired of bodging up temporary fixtures to relieve the center portion of connecting rods that today I actually took an hour and built a dedicated fixture for it. I will post a clearer picture of it when I get the other side of the rod finished. It works like a charm.


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