-90 Burb is going to get the C

[ttammeslehto]

Put the crank on a scale to get the weight before any work done for it. The scale showed 55. 8 kg/122. 8 lbs. Also drilled the pilot hole, going to drill them step by step up to around 34mm/1. 34" and decide when to stop when getting closer and closer



Timo

 

[sbentz]

We took over 10 pounds out of a crank and never even pin drilled it. You could not even see much difference! There is a lot of room to lighten these...

Cheers, and thx for the beers, Timo!

 

[ttammeslehto]

You're welcome Scott, hopefully your wife didn't finished it all before you got back home :-laf

Alright, lets continue work with the crank. Grind a drill bit to have a guide (12mm) to keep it center in the hole while drilling and finished first one up to 32mm.

Timo

 

[GOT-Torque]

Awesome work, love reading about your progress...



where exactly do I ship my crank to? :-laf

 

[ttammeslehto]

Well, I don't take ordes yet :-laf

Second hole done, weighted the crank and it's now 500g (1. 1 lbs) lighter, so one hole reduces 250g that times six makes 1. 5kg (3. 3lbs) but it's going to be more lighter when all the work is done. Turned it upside down and did the drawings for the two rearmost journals. These two require some mods for the drill bit due to flange on the way.

Timo

 

[HoleshotHolset]

Wow - it takes a lot of nerve to drill gaping holes in a perfectly good crank. Well done.



Beers,



Matt - Suomi!

 

[ttammeslehto]

First hole done to the rear of the crank, the drill bit needed some grinding due to flange.



Timo

 

[ttammeslehto]

One more pilot hole has been drilled, with really long 12mm drill bit. Two middle ones are drawn and are next on the list. Bathroom renovation is hitting my garage time badly, but trying to sneak out whenever possible. :-laf



Timo

 

[sbentz]

The argument that I got into with my crank guy, is why not cut half or all of the counterweights off? I have one 12V crank that we lightened by 15lbs. Cannot even tell it by looking. There is a lot of material that could come off.

 

[ttammeslehto]

If you cut the counterweights off, how do you balance the crank?

 

[BAnsley]

your counter weights off set the weight of the other side of the crank and the componets bearings,rod,wristpin,clips,and pistonand give or take a few ounces of oil. put all of these parts on a scale and you soon see why the counter weights are as large as they are.

 

[sbentz]

your counter weights off set the weight of the other side of the crank and the componets bearings,rod,wristpin,clips,and pistonand give or take a few ounces of oil. put all of these parts on a scale and you soon see why the counter weights are as large as they are.

You are right for a V-8 or other V design. When balancing a inline 6, the crank needs to bob weights added. just a simple balance. Same with rods and pistons. Individual balance, no calcualtions needed.



My comment on counterweights is that there are some inline 6 engines without any counterweights. Some with some, and some with full counterwights depending on the harmonics you want to balance out.....

 

[ttammeslehto]

It’s been weeks, since I had some time off to work with the crank. What’s left to drill, are the two centremost journals. To reach them I need to drill through counterweights of #1 journal. This is where lasers become really handy.

 

[Gary - K7GLD]

JEEZE, I just LOVE guys with the knowledge, or sheer GUTS to actually dig in and GITTERDONE, instead of just sitting back in their armchairs and taking disruptive critical potshots based upon pure opinion and baseless theory! :-{}



GREAT work!

 

[ttammeslehto]

Thanks Gary!



Second last done. I needed to cut open the hole on a lower counter weight to be able to swing the drill bit on its place.



Timo

 

[GOT-Torque]

Awesome work, I love the pics...

 

[ttammeslehto]

Last hole for the crank is now drilled. Next thing to do is to polish all the drilled holes to get rid of scratches left by the drill bit. Those nicks could be a start points for cracks if not grinded off. On the pics you could see how I use the laser to find out oil riffle on the journal and marked it up. Also you could use it to mark the points where to drill through counter weights to reach the journal. Last pic is the crank, “fresh from the drill” all that metal shaving is from the crank.



Timo

 

[ttammeslehto]

Been a long time since the last post to this forum, but been busy with other things. Suburban is doing great with the current engine and like you know, the next Cummins is under work to be swapped in at some point. Have had a few short moments to continue work with the crank lightening. After drilling the journals I decided to cut off the counterweights too. (Scott, this is partly your fault, you shouldn't ask me, are going to cut counterweights off too... . ) well, what I got to lose,really. Just a crank, 50h of labor and if it happens to break at the moment when the smoke is greatest, boost up to the sky high, it will most likely blow up everything else than the alternator, so, what the heck. I just start all over again.

With a big and small angle grinder I cut off much as possible from the counter weights, it lightened about 6kg/13. 3lbs more. The drilling already took off around 5. 5kg/12lbs. That makes total 11. 5kg/25. 4lbs off the weight, naturally it going to lose more because counterweights need allot of milling to make them nice and smooth.



Timo

 

[sbentz]

Looking good! Glad to see you are still at this. Best to you and happy holidays!

 

[HoleshotHolset]

Timo - now the counterweights are coming off? You're brave.

What's next? Are you going with a lightweight titanium alloy?



Beers,



Matt