Project of the Month built by apointofview
Home Model Engine Machinist > Showing Them > A Work In Progress > Rupnow Ovehead Cam Air Cooled

Reply
 
Thread Tools Display Modes
Old 02-16-2017, 02:53 PM   #61
Brian Rupnow
Project of the Month Winner!!!
 
Join Date: May 2008
Location: Barrie, Ontario Canada
Posts: 9,338
Liked 3475 Times on 2901 Posts
Likes Given: 36

Default

This morning I have a piston on the go. It is going to be made from cast iron. Why?---Because when I buy cast iron to make cylinders from, I always buy a piece about 3" longer than I really need, so I have something to hang onto with the lathe chuck while the cylinder is being machined. All these left over bits from making cylinders eventually get recycled into pistons. I could have use aluminum and it would have worked just as well, but I didn't have any aluminum the right size. The outside diameter is turned to be 0.003" larger than the bore of the cylinder. That over-size will get addressed a bit later. I have put the round counterbore into the "open" end of the piston, and cut the ring groove with my .094" wide parting off tool. My next step will be to hone the inner bore of the cylinder with my 3 stone brake cylinder hone to knock down any high spots inside the bore (which was put in with a 1" reamer). Then I will "dress" the piston with 280 grit carborundum paper strips while it is still set up in the lathe until it just starts to act like it might fit into the end of the cylinder, but doesn't slide freely in. At that point I will remove the piston from the lathe and set it up in the chuck on my rotary table to complete the machining operations.


__________________
Brian Rupnow
Brian Rupnow is offline  
 
Reply With Quote
Old 02-16-2017, 06:34 PM   #62
Brian Rupnow
Project of the Month Winner!!!
 
Join Date: May 2008
Location: Barrie, Ontario Canada
Posts: 9,338
Liked 3475 Times on 2901 Posts
Likes Given: 36

Default

Remember how I said that you just want the piston to start into the cylinder, but not slide all the way in. All of the other machining operations are then finished on the piston, and my "special tool" which has a wrist pin sized cross hole in the end is slid into the piston, a dummy wrist pin is pushed into place and locked there with the wrist pin retaining screws. The piston is then coated with green diamond lapping compound, and then the piston is "wrung" into the cylinder in a sliding, twisting motion. I always find that this part is much harder and takes longer than I think it will. After an hour of pushing and twisting, and occasionally having to run out to the arbor press to get the piston "unstuck", the piston will go all of the way thru the cylinder, and is virtually an air tight seal. It would probably run this way with no ring on the piston at all. I will now wash the inside of the cylinder and the outside of the piston with laquer thinners and an old toothbrush to remove any remaining diamond compound, and move on to machining a connecting rod.


__________________
Brian Rupnow
Brian Rupnow is offline  
 
Reply With Quote
Old 02-17-2017, 03:41 PM   #63
Brian Rupnow
Project of the Month Winner!!!
 
Join Date: May 2008
Location: Barrie, Ontario Canada
Posts: 9,338
Liked 3475 Times on 2901 Posts
Likes Given: 36

Default

I had almost finished this connecting rod yesterday, but after almost 12 hours in the shop I was quite happy to quit for the day when my wife got home at 7:45 from her job. Today I did the final clean-up and fettling on it and it is finished. The picture shows it setting with two tiny sealed ball bearings in the wrist pin end, and an oilite bronze bushing in the crankshaft end. My hands are sore today from wringing the piston into the cylinder yesterday.
__________________
Brian Rupnow
Brian Rupnow is offline  
 
Reply With Quote
Old 02-18-2017, 01:34 AM   #64
Brian Rupnow
Project of the Month Winner!!!
 
Join Date: May 2008
Location: Barrie, Ontario Canada
Posts: 9,338
Liked 3475 Times on 2901 Posts
Likes Given: 36

Default

Today I made crankshaft webs. I didn't originally plan on having counterweighted webs, but the weight of that cast iron piston really surprised me. I have been making pistons from aluminum for so long that I forgot how heavy a cast iron piston could be. I decided that this engine would need counterweights to offset the weight of the piston. The webs are made from 5/16" 1018 flat bar. I didn't realize it when I designed this engine, but 5/16" flatbar is not something commonly stocked by Barrie Welding where I buy most of my material. I ended up getting 3/8" flatbar and flycutting 1/32" from both sides to keep it from warping. Three of the holes are reamed to 0.3735", and one is drilled to 5/16". I will make the crankshaft from 01 drill rod, not because it has to be hardened, but because drill rod comes in at on size to .0005" over, while cold rolled 1018 comes in .0005" undersize. When you are pressing crankshafts together instead of machining from solid, that .001" difference between drill rod and plain cold rolled rod makes a big difference on how well the crankshaft stays together. The rod journal will be machined from 3/8" drill rod, and pressed into the driver side web. The main body of the journal that the rod sets on will be turned to 0.3125". This is going to be a two piece crankshaft, with a driver side and a driven side. The end of the rod journal that fits into the 5/16" drilled hole in the driven side web is a clearance fit.
__________________
Brian Rupnow
Brian Rupnow is offline  
 
Reply With Quote
Old 02-18-2017, 05:27 PM   #65
Brian Rupnow
Project of the Month Winner!!!
 
Join Date: May 2008
Location: Barrie, Ontario Canada
Posts: 9,338
Liked 3475 Times on 2901 Posts
Likes Given: 36

Default

Houston, we have a ---crankshaft!!! One thing to be aware of when using drill rod for crankshafts. Since it is .0005" oversize, it won't fit thru the 3/8" ball bearings. The trick here is to determine exactly how much of the shaft must go thru the bearings (in my case, all of the shaft that isn't pressed into the webs), put it in the lathe, and work it down over its full length with 220 grit carborundum cloth strips. This is not hard to do, it's just time intensive and requires a lot of "Stop the lathe and try the bearing to see if it fits onto the shaft yet". The end of the shaft which is getting pressed into a 5/16" web plate is left 15/16" long, and not touched with the carborundum cloth. Turn down 5/16" of length at the end to .372". Then turn the next 5/16" down to 0.374". Use a thin strip of carborundum cloth to smooth the shoulder which results being 3 different diameters. Clean the parts which get pressed together with laquer thinners and a Q tip. The press fit is going to be more than a 2 ton arbor press is going to be able to handle. This pressing gets done in my big shop vice. You need a hollow socket or something to accommodate the part of the shaft which has been turned undersize because it is going to "stick thru" about 5/8" on the wrong side of the web when the pressing is completed. coat all the areas of the shaft which are going to be pressed with 620 Loctite, and have at it. After the shaft has moved about half way home, loosen of the vice in case things are going a bit crooked, then take it the rest of the way home. this is a very hard press fit. Trim the "stick thru" part with hacksaw or in the lathe, and you're done.
__________________
Brian Rupnow
Brian Rupnow is offline  
Ghosty Likes This 
Reply With Quote
Old Yesterday, 11:57 PM   #66
Brian Rupnow
Project of the Month Winner!!!
 
Join Date: May 2008
Location: Barrie, Ontario Canada
Posts: 9,338
Liked 3475 Times on 2901 Posts
Likes Given: 36

Default

There is an undefined point when a craft begins to become art. These sidepates are getting pretty close to that point. I like them a lot. I know that there is two full days of work in getting them to this stage. The engine will look a lot more balanced once the gas tank is completed and fitted to it.----Brian


__________________
Brian Rupnow
Brian Rupnow is offline  
2
People Like This 
Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Water Cooled Webster bmac2 A Work In Progress 268 10-01-2015 12:44 PM
4 Cylinder Air Cooled Draw-Tech A Work In Progress 6 02-15-2013 01:15 PM
Red Wing Air cooled. Brian Thomas Finished Projects 12 04-13-2012 01:42 AM
Air Cooled H&M chads Engines From Castings 7 08-24-2011 02:41 PM
Air Cooled Red Wing Mike N Engines From Castings 13 02-05-2010 01:19 AM





Newest Threads






- Top - Member List