new guy - with crankshaft conversion question

[flydog]

Hey all. New to the board.
I've got the Milholland 1/2 vw plans but can make no sense of what is going on at the cut end of the crank.
Could anyone explain it better, or put up a drawing, or pictures?
Tnx
Phil

[Steve]

Most guys by a crank converted from DeMello Cranks or Scott Casler of Hummel engines and you advise them you are doing the BetterhalfVw conversion...

Here's pictures of a guy doing the BetterHalfVW conversion on a 69mm German forged crank: http://airplanesathome.com/component/option,com_gallery2/Itemid,38/?g2_itemId=1183

This is the conversion of a performance stroker crank such as is sold by Scat or Empi :

Good luck with your build,
Steve

[John Harmon]

I have left messages at every number I could find for DeMello. Based on a lack of responses, I wonder is this place still in business? Does anyone havea number they are sure of?

[Steve]

I have left messages at every number I could find for DeMello. Based on a lack of responses, I wonder is this place still in business? Does anyone havea number they are sure of?

Almost universally manufacturing shuts-down in S. CA for the Christmas/New Years week or two... DeMello is an administration case study - if you don't speak with Bob or son - call back... The last known address and tel # is here: Contact page posted Oct, 2010
Steve

[nheistand]

The thrust bearing (with the flanges) is normally next to the flywheel with some washer/shims to get the crankshaft "end play" at about .003 to .005 in. On a standard VW if you grab the flywheel and push and pull it, you will feel that there is some clearance for the crank to move a little. This is necessary since the heat expansion rates of the case and the crank are different. The other thing the thrust bearing does is withstand the driver pushing the clutch down. With our flying VW we need the thrust bearing to withstand the prop pull.  The Millholland 1/2VW cuts the crank just past the middle bearing and installs the flanged thrust bearing on that bearing. Now the end of the crank is drilled and tapped for a bolt so a round aluminum plate can be bolted to the end of the crank. Now shims can be used under the plate, next to the bearing flange to set the end play. So the two flanges on the main bearing control the crank thrust in both directions. (pusher or tractor prop?)

Norm Heistand  my .02

[Steve_]

Hey all. New to the board.
I've got the Milholland 1/2 vw plans but can make no sense of what is going on at the cut end of the crank.
Could anyone explain it better, or put up a drawing, or pictures?
Tnx
Phil

Phil:
Two annotated photos attached show my DeMello made BetterHalf crank and the further machining done at The BugPatch, Santee, CA to take Tractor or Pusher thrust at the # 3 main bearing using 6 washers (3 on each side of the bearing)...
Steve

[flydog]

Thanks for all the replies. Think I see what hes doing now. His drawing of the crank, and the description of it
left me just a little bewildered.
'Cut shaft on A"  Cool,understand.
"machine on B for end play and end plate end play...."    uhh, what?

So I see now he machines the throw(?) part of the crank down till it looks like an extension of the #2 main bearing, and then machines it to a length to controll end play. Some pictures Ive seen it (the machined area) steps down a little (smaller diameter than #3 bearing area.
Since Millholand doesnt specify a diameter in this area does it matter if i steps down, is same diam, or even bigger than the jornal dimension?

[Steve]

Thanks for all the replies. Think I see what hes doing now. His drawing of the crank, and the description of it
left me just a little bewildered.
'Cut shaft on A"  Cool,understand.
"machine on B for end play and end plate end play...."    uhh, what?

So I see now he machines the throw(?) part of the crank down till it looks like an extension of the #2 main bearing, and then machines it to a length to controll end play. Some pictures Ive seen it (the machined area) steps down a little (smaller diameter than #3 bearing area.
Since Millholand doesnt specify a diameter in this area does it matter if i steps down, is same diam, or even bigger than the jornal dimension?

Phil:
I really began to understand it when I took a scrap engine apart and my machinist pointed out he didn't have tooling or cnc setups to make the Brazilian case take a thrust bearing at #2 saddle - some of the older cases will... Anyway, an AirVW in this part of the country gets the thrust taken at #3 main - just because - you don't want to know why... So, if you are doing a #2 main bearing thrust setup, take a junk #1 main bearing and see if you can seat it there...
Steve

[nheistand]

Looking at the photos, it reallly does not make any sense to add the plate to the end of the crank. At first I thought the thrust bearing would be at the end of the crank, but in the photo the thrust bearing is by the cam gear. This seems like mixing two different methods to control the end play. I would expect that you either control the thrust at the cam gear or you control it at the end of the crank. I have plans that use two thrust bearing shells. One gets one flange cut off and put by the cam gear. The other goes at the end of the crank. This will leave zero end play. Then the bearing at the end of the crank is machined or sanded on the inside flange until you have the desired clearance. This method does not use any shims, instead adjusts the thickness of the bearing flange. I like this better since the only machining I can do myself with sandpaper. It does however require buying two sets of main bearings to get the two thrust bearing shells.

Norm Heistand  my .02

[Steve]

Looking at the photos, it reallly does not make any sense to add the plate to the end of the crank. At first I thought the thrust bearing would be at the end of the crank, but in the photo the thrust bearing is by the cam gear. This seems like mixing two different methods to control the end play. I would expect that you either control the thrust at the cam gear or you control it at the end of the crank. I have plans that use two thrust bearing shells. One gets one flange cut off and put by the cam gear. The other goes at the end of the crank. This will leave zero end play. Then the bearing at the end of the crank is machined or sanded on the inside flange until you have the desired clearance. This method does not use any shims, instead adjusts the thickness of the bearing flange. I like this better since the only machining I can do myself with sandpaper. It does however require buying two sets of main bearings to get the two thrust bearing shells.

Norm Heistand  my .02

The crank was converted to BetterHalfVw plan interpretation by DeMello... Then the new case came from Brazil and was found to have a #2 main bearing saddle that wouldn't take the thrust bearing shell... The oil gallery plug in the end of the crank depended on the thrust washer to retain it so the thrust washer system was used for another reason...

A thrust system without the the three washers will wear out fast - the flanges on the standard bearings won't take scrubbing abuse...

[Sparrow]

Hi Norm,
 
I am certainly not an expert regarding the VW but I worked with Glyco in Wiesbaden, Germany for years helping develop methods of bearing manufacture and also in the United States for Federal-Mogul.  My concern regarding separating the thrust loading by the span you indicate is the thermal characteristics that will take place during regular engine operation.  Generally you want to keep the thrust bearing in a single location and you want to limit the distance between the thrust elements.  Generally the linear increase of the steel and the bearing material is given as an inch per inch degree Fahrenheit or Centigrade.  The softer aluminum will grow faster than the forging but you have more linear inches in the separation caused by the radial bearing element between the two thrust surfaces.  The steel will grow at about 1/2 that of the bearing material but there is a greater linear distance which becomes the multiplier for total growth or contraction as the temperature changes.  Separating the two thrust elements by having one trust at bearing location 2 and one at bearing location 3 is filled with many unwanted influences across that span.  Not only do you have the pure linear distance of the steel member but you also have a twisting that can occur because of the changing cross sections of the crank shaft as it accommodates the piston throws.  It is for these reasons that I would not do this.  The more stable setup is to incorporate the push pull axial thrust load carrying abilities into one main bearing location.  This is why all engines have a single thrust bearing and all other main bearings are radial and only carry radial loads.  The engines are designed to allow for clearance along the sides of the regular main bearings so the crank shaft can grow and flex without causing a loss of oil film thickness and have a bearing touch down occur and wipe a bearing out.  I have worked with diesel applications where all the crank shaft journals were pure radial load carrying elements only and there were machined into the crank shaft a thrust collar that would have thrust bearing washer elements on both sides of this collar.  The entire crank shaft can move around along its axis and not disturb the thrust elements.
 
I do hope this makes sense and if anyone has any questions regarding this please ask.  An engine is a living breathing structure and most everything is designed to compensate for thermal movements and stress loading for the entire system and not cause clearance issues in any given location. 
 
Cheers,
 
John