Boat-tail/knife edge counter weights & rod throws Q's

[theastronaut]

Here's a better pic of the shape of a leading edge:





And a few of a trailing edge:

One side rough shaped and smoothed with sanding drum.




Both sides shaped and smoothed with flap wheel.

[theastronaut]

Half of the counterweights are done and I've started on the rod throws.

Shape before, square corners:





Rough shaped (left half of throw only):











Smoothed with flap wheel, hand sanding with 320 and 500 grit:









More tomorrow...

[Bruce2]

.... hand sanding with 320 and 500 grit...

Don't waste your time with the 500 grit.

[theastronaut]

Finished the first rod throw:

[Bugfuel]

Re: wasting your time on finish..... if your labor cost is $0.00, go ahead and do the best you can. Bragging rights are worth something too Unless you have something better to do with your time.

[Bruce2]

Think about what else you could do with that time rather than valuing your time at $0.00/hr.

Suggestion: Leave the 500 grit sanding until the whole thing is done, then ask yourself if it's worth it or would you like to move onto the next project.

[theastronaut]

The 500 grit takes very little time once it's been sanded with 320 grit. The 320 takes far longer than sanding with 500 grit. It just makes it look much better, the sanding scratches are way less visible. But...

Bruce, here's a pic just for you! If 500 grit is a little extreme then I'd like to see what you've got to say about this! I got inspired by your post, decided to go above and beyond the call of duty and whipped out my 3 inch D/A sander with 2000 and 4000 grit wetsanding pads, then hand buffed it with Wenol metal polish...

I don't think its possible for something to be too polished.

[Bugfuel]

LOL!!

THAT'S more like it! hehehehe

I once polished piston tops for my 1600 experimental engine, you could see a reflection of a coke bottle on them The idea was that it would minimize carbon buildup and maybe reflect the heat into the head more. At least the piston tops stayed pretty clean, the engine was torn down twice a year for inspection and further mods. It was a high compression engine with a tight deck, and careful tuning so carbon buildup may not have been an issue to begin with. Tight deck tends to help the piston tops clean too.

[theastronaut]

A little more progress:

[bradey bunch]

If there was an award for most beautiful crankshaft, this would get it! Looks good.

[theastronaut]

Haven't had much time to work on the crank lately but did get this much accomplished. Started smoothing the inner rod throws, these things are thick! Working around the oil passage plug turned out to be no problem as the plug seats much deeper that I originaly thought it did. Hopefully all of the plugs are tapped this deep. Some of the pics have show a white cloth wrapped around part of the crank; the reflection of the black opposing rod throw cheek makes it hard to see the shape of the polished rod throw. Its hard to get a pic that shows the shape of the crank because all the camera pics up is the reflection.

The original shape; rather squared off and chunky:



The shape was also uneven side to side.





Roughly matched up for a better starting point:



Rounded, smoothed, and polished:











The opposing rod throw arm shaped and polished, theres a peak running diagonaly down the length of the rod throw separating the inner and outer shapes; its hard to get a good pic of it.

[fusername]

sexy does not begin to cover how nice that looks. I would be scared shitless of doing that to my own stuff, looks too weak around the edges to me, but polishing the face like that will do wonders for stopping cracks from forming, i doubt its wasted effort. Really curiuos how long this lasts. maybe for my next off road motor i will give this a shot if this one does ok. I would still get it balanced when i was done tho.

[theastronaut]

sexy does not begin to cover how nice that looks. I would be scared shitless of doing that to my own stuff, looks too weak around the edges to me, but polishing the face like that will do wonders for stopping cracks from forming, i doubt its wasted effort. Really curiuos how long this lasts. maybe for my next off road motor i will give this a shot if this one does ok. I would still get it balanced when i was done tho.

Thanks! It will definitly get balanced once I'm done shaping and polishing (along with the rods, pistons, flywheel, pulley, etc...), although I'm not looking foward to seeing what it will look like when they are finished. The edges of the rod throws are thinned down to the rod thrust surface but I added a slight radius at the edge instead of leaving it sharp. Seeing how think the rod throw arms are, I'm not worried about the overall strength of the crank; in fact I think that the reduced weight of the rod throws would decrease crank flex at higher rpms.

[disturbthepeace]

Good job on the crank so far but I do have to agree that the 500 grid is a little overkill. I've done three VW cranks like this so far with no balancing issues or failures, including the one that's in my 1915 turbo motor. 

Just a little tip for the future is that if you aiming for aerodynamics gains that the shape would be more beneficial if it had a more blunt face with a tapered tail, like an airplane wing. I did some reading on crank throws and most the experts agree on this theory. But that wouldnt help much with wasted energy cutting through the oil so most V8 high dollar builds use dry sumps and/or custom Windage tray systems.   I toke the info to mind in my cuts and just rolled back the front edges and tappered the trailing.  Also rolled back the rod throws but not soo much that it would have the potential to weaken the crank. Also I didn't have any heat treatment done afterwards, just had it balanced. 

My tool of choice was the same thing I use on V8 cranks, I standard grinding disc on a body grinder, then polished with a 3M abrasive buffing pad. 

Good luck

Joe

[disturbthepeace]

My last post was sent form my iphone and it didnt load 3/4 of the pix. Now that im on my laptop I see you have got the trailing edges of your CW knifed... WTG

Should work great, polishing is overkill though. Best case all that shine is gonna gain you .6 hp(just a guess) dont get too intense with it because all that energy would be best used on the heads, chambers, pistons or something that will gain you some real HP for the effort...


Joe