Posted by Sam M. on Thursday, May 29, 2008 @ 10:43 PM:
We got some bad news the other day, are crank has a few minor cracks in it.
does anyone have a crack/damage free 1200cc airplane crankshaft that they want to sell us?
Does anyone still make 1200cc airplane crankshafts?
thanks Sam
[Edit by Sam M. on Thursday, May 29, 2008 @ 10:44 PM]
Posted by andy1 on Friday, May 30, 2008 @ 03:39 AM:
To my understanding the Rectimo 4AR1200 engine has a standard VW1200 crank. These should still be available via Volkswagen.
-A-
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Posted by rshoover on Friday, May 30, 2008 @ 10:34 AM:
The stock 1300/1500/1600 crankcase (ie, 69mm throws) fits the 1200 crankcase. New, VW crank is presently about $125 in southern California. I don't know of any new 64mm cranks being available here; possibly in Europe, where the 1200 remained an option into the late 1970's (VOA, the importer of VW vehicles to the USA stopped importing vehicles fitted with the 1200 engine about 1965.)
A stock, after-market 69mm crank (Bruck) has a street price of about $90. Quite a few of these tucked away at the back of various shelves.
The fact the crank fits the 40-horse case doesn't mean it's a bolt-up. The big-end of forty-horse rods is 1mm wider than later rods, meaning you'll want to run them through the surface-grinder. If the rods are 401's you can take the meat off one side but for the later 401A's you'll want to take half from each side, since the center-line of the little-end is off-set on 401A's. Jack Riddle's shop in Santa Ana is probably your best option for such work. Jack is no longer with us but Riddle Machine Company (aka 'RIMCO') remains the largest and most experienced shop for work on air-cooled VW engines.
Since the 40-hp case is about 3/4" narrower than the later crankcase, you'll need to add a spacer under the barrels and re-set your valve-train geometry, relatively trivial chores. With .010" barrel spacers the CR will be about 8:1. If you'd like to drop it, see any of the numerous articles on adjusting compression ratio. (There's one in my blog.) The added 5mm of stroke results in an engine having a displacement of about 1286cc (ie, the same as the 1300 engine).
Forty-horse rods also use a smaller piston-pin, 20mm vs the later 22mm. They are also 7mm shorter than later rods. This argues against using later rods & jugs unless you're willing to bear the necessary expense. As it is, the 130mm center-to-center length of 40hp rods puts them right at the limit for a 69mm crank (ie, as defined by the Ricardo Rule).
Should you wish to punch it out to accept larger jugs, RIMCO is probably your best choice. They will try to discourage you from doing so with a 40hp case since it's not as strong as the later crankcase. In a similar vein, the increased displacement will only improve your PEAK output, which you may enjoy for about four minutes during take-off. After that, the engine's sustainable output is determined by the surface area of the fins on the heads, which is typically between 35 hp and 45 hp REGARDLESS of displacement. (Variation reflects the local atmosphere. For Standard Day conditions, maximum sustainable output is about 40bhp.)
-R.S.Hoover
Posted by Sam M. on Friday, May 30, 2008 @ 01:05 PM:
andy,
our crankshaft has some machining done to accept the prop hub,
we have source for a 1200cc crank, but we were hoping we could buy one already machined,
I will pass this all allong to my dad,
thanks!!
-sam
Posted by Collin on Friday, May 30, 2008 @ 02:55 PM:
Sam,
I have a new 1200 crank. Monday I was planing to sending Great Planes a 1600 crank to have the nose machined for the rectimo prop hub. They charged $75 last time I had it done. I also just got off the phone with Great Planes, they said about two week turn around.
Collin
Posted by Jorgen on Friday, May 30, 2008 @ 04:58 PM:
Good luck with your crank, Sam. It´s a good thing VW parts are a good deal cheaper than ordinary aeroengine stuff.
Mr Hoover, as you comment on your blog, the late Bob Hoover the "Shrike-glider pilot" and expert backhand coffee-pourer might have been the most gifted pilot roaming the atmosphere, but I bet he didn´t have anything on you regarding VW engines. Nice to have you on the forum and thanks for your inputs.
Take 5(b) just 4 fun/ Jörgen, SE-UDI, SE-XST
