|View single post by Terry Bentley|
|Posted: Sat May 19th, 2012 05:40 am||
|I heartfully apologize for getting sidetracked and not having anything added specific to the Clinton yet. I am looking forward to having one version of this motor finished soon enough tho. Might not be the removable head with motoplat model, but the other one will do for now. I surely dont want Dave to suffer any withdrawals, not getting his fix either. I hear the pain can be sometimes unbearable. So can at least add some general stuff I was working on tonite and hopefully have more specific to the thread posting not too far down the road. Below is the arbor press I would normally use to press three or multiple piece cranks apart. This may include most foreign kart engines, motorcycle and even Seadoo crank assemblies.
This dog of a press stands nealy seven feet tall. The 1 1/4" diameter cheater bar handle is about six feet in length for some decent leverage and managed to have sliced a hole in ceiling when at rest. This particular model is a ratcheting compound arbor press.
By sliding the pin thru, I can get over 30 tons of leverage to do just about anything. This type of press dwarfs any of the conventional hydraulic presses out there. Doesnt matter how many tons of one it is either. The down side to a hydraulic press is having to build up fluid pressure until it overcomes the resistance its being used for. Can easliy be a lethal weapon in the wrong untrained hands when something decides to let go. Been there done that and gratefully had moved before I became one with nature. Someone up there has always been keeping an eye on me when I have done things. Either press fitting something, crimping, smashing or forcing something that isnt supposed to fit or cutting key slots. Many uses. This press is great in converting pre 1982 pennies into nice thin copper washers or shim stock.
I havent used this much during the past 10 years, so it just sits on floor and collects rust. A simple fixture to press multi three piece crank assemblies apart. In the foreign engine build that will be coming forthwith, I will cover in detail how to press apart, and reassemble the crank, including alignment on centers, not V blocks, with dial indicators.
But the press has so many other uses as well. Here is what I was sidetracked on and finishing up this evening.
The piece of sheet metal at rear is 1mm(0.039") thick 4130 chromoloy. Sells for around $12 as pictured. Originally just a flat stamped piece of sheet metal. Lets call it an "AK flat" just for ease of identification. What I need to do is bend this AK flat up on both sides to form a channel about 1 1/4" across the inside width. This is my version of a first generation jig I built out of improvised scrap laying around, from a picture found on the internet. The original one was just able to fold the AK flat into a channel as we will soon see happen. Early AK flats were as the name implies "flat". The finished product would also need to have both sides to include a small lip folded in on top. We will call these lips the "top rails". I added to the basic setup to be able and do just that after the channel shape was achieved. While still pushed thru, I could swap top plate around then add an arm that would fold the top lip(top rail) as needed. Newer AK flats came with the top rails already folded, making for all of the extra pieces no longer needed. But fixture served its purpose well until the newer AK flats became available. This is the only fixture of type that could also bend the top rails in existence. But now is no longer a needed function. So much for trying to be creative.
By assembling the pieces of stock together we get the general shape of what the AK flat will be patterned after.
First the center section with both side plates attached, then both top and bottom plates bolted. There are two small locating holes on AK flat that line up with pins press fit in bottom of center section. You will notice the AK flat has dimples and holes all over. The side plates are both cut for clearance at each matching location.
Here is everything bolted snugly together. The AK flat can be seen right above bottom plate. Now we get to do some collateral damage.
Moving over to the arbor press. You can see the AK flat better and it bolted to the plates. The large flat topped frame with rectangular hole is what the AK flat is going to get pushed thru. Can be referred to as the press block or die. It is nothing more than 1/4" thick 3" angle iron. Originally part of a torn down steel building. Pieces cut and welded together, then all controlling surfaces machined to exact spec size for part. The jigs and fixtures could have all been cleaned up and painted with red oxide to give them that professional look. But would have served no functioning practical purpose, especially since i dont offer tours in the shop.
The bottom plate is sandwiching the AK flat to center section. It is same outside dimension as finished product, which also serves to give perfect alignment in the press block it is fitted in. The large ram of arbor press is resting on a piece of aluminum scrap cut at same angle as finished part will be shaped. About 2 1/2 degrees of angle, for those inquiring minds.
Now exerting downward pressure on ram the AK flat breaks its flat shape then is forced thru the opening in press block.
Its pushed completely thru. Without the need to bend the top rails anymore this design of fixture is completely obsolete. Otherwise I would be flipping over the top plate and adding a lever to bend the top rails. A newer and so much simpler design is nothing more than a finished sized plate pushing thru a machined channel that breaks both sides of AK flat over to desired finished channel shape.
The AK flat is no longer flat. Once the edges broke, as in bent over, it took little force to push thru.
Being that the top plate of fixure is longer than opening in press block and doesnt fit thru, was removed in order to push this all the way out bottom. Lower plate can now be unbolted and removed. The small black screws at each end are then removed. This allows that center section to slide right out the top between the small top rails that were already prebent. The outer plates can now fall out.
Here is the result of all that work. This is a DIY type of build, not mass production. Fortunately the jigs and fixtures dont take very long to build or would be very time/cost prohibitive to do a small number of build ups of parts such as these. It took 1/4th the time to bend these last two flats I had left over than did to write and upload the pics here on this post. But the AK flat can no longer be called a flat. It is now considered by the BATF a restricted firearm exactly as is pictured, just as you see it. Legal for me to build and 922r compliant, but not legal for me to sell. Go figure. I would enjoy doing a complete writeup on the whole project and will get it all finished. But here is not the place for it to be posted. This is just a small taste of what can be done with a little mechanical ability and basic equipment. Not to mention the world wide web as a 24/7 ready to access library at your fingertips.
NOTE: There are many ways to achieve this task set forth here. At the time I was building a bunch of these without top rails prebent, This was one direction I pursued. Its function was to bend the channel shape and while still pressed in the block, I could add a swing arm that would bend the top rail perfectly square and identical on both sides without changing jig or fixture components already built. in existing setup. It worked well for me and results were precise and exactly as expected. Your results may vary.
Last edited on Sat May 19th, 2012 07:24 am by Terry Bentley