Crankshaft Offset Journal Test Part Machining

We left off on the crankshafts with all the lathe operations being complete and all 4 parts being ready for the 4 axis mill work.

The next operation is to do the offset machining needed for the connecting rod journals.  There are two techniques available: eccentrically mount the crankshaft in a special chuck on the connecting rod axis and turn the journal or mount the crankshaft on the main journals and eccentrically turn the conrod journal.  The first option is easier to program but more difficult to fixture, is very unbalanced during machining, and requires part repositioning for each conrod throw.  The 2nd option is more complicated from a programming perspective but is easier to fixture, is balanced, and needs no part repositioning.  I chose the 2nd option as once the upfront programming work is done making multiples is easy and repeatable.

Due to the low cutting forces due to the aluminum test part material and a desire to get a sample part machined I opted to leave the outboard 4th axis support off.  Machine time these days is limited and getting a sample part quickly was of prime importance.

The mill setup is as shown:

The first operations are simple pocketing to remove the majority of the material in the most efficient machining technique.  Pocketing was done at increments of 90 degrees and ended up with squarish journals.

 

Here's a short movie of the squared off journals:


Once this stage was complete I moved on to the 2nd program which created the fully round journals.  The video of this move is subtle but cool.  The machine is performing a G3 arc in the YZ plane (G19) while the 4th axis is doing a rotary move from 0 to 360 degrees.  The result is an eccentric true cylindrical surface with none of the approximation concerns usually associated with surface machining type toolpaths.

This is the first journal after its finishing pass.

And this is a short movie of both journals.

The 3 slight ridges on each journal are an artifact of the dished end of the end mill used for the test cut.  For the final steel parts I had a 4 flute finishing end mill specially modified to flatten the end face and keep it center cutting.  It is not suitable for machining aluminum so in the interest of quickly getting a verified program I used a mill with standard aluminum cutting end geometry.

This part is being sent to a grinding house for finishing of the journals so the absolute tolerance and surface finish are not as crucial as long as there is enough stock left to clean up during grinding.  After consulting with the grinder I am leaving .010" of stock on the main journals and .020" on the connecting rod journals as grinding allowance.

Now that I have a sample crankshaft we can test assemble a short block with the major rotating components: crank, conrods, pistons, and also trans and oil pump/drive components.  Once we reach that stage there will be lots of pictures!

That's all for now.

Chris

Machining the Torque Plate

I was able to get at Peter's mill for a bit last night and did the machining on the torque plate.  This part is used during the final cylinder honing process to simulate the distortion of the bore caused by the cylinder head bolt forces.  It is useless to create a perfectly circular bore if you are then going to distort it with clamping forces. This procedure creates a more accurate simulation of real world use during the bore process that results in an out of round cylinder when unclamped that shifts to round as it is clamped.  I've heard that extreme tech engines like F1 do the honing process with a torque plate while the block is heated with hot water to even more closely replicate actual operating conditions.  I'll have to see what MT thinks about this one!


The part started with a piece of 1" thick 304 stainless steel plate that was waterjet to a rough profile by North Eastern Water Jet.  Andre of NEWJ is always very helpful in suggesting material they already have in stock to shorten lead time and reduce cost.  The cost of the waterjet cut blank from NEWJ was less than a comparable piece of stock from the local supply house and saved me from having to hog out the majority of the cylinder bore.

The machining of the bores and screw/dowel holes was uneventful.  The part is now nearly finished.  The last issue is that the mill finish on the top of the material is not fine enough to clamp on the head surface without marring the aluminum casting.  To fix this the part needs to be surface ground to a 8 microinch finish.  I'll bring the part to a local vendor, Garden State Precision, who has the equipment and expertise necessary to do the job properly.   I'll drop it off in a day or 2 and since this is not a rush pick it up in a week or 2.

While I am at GSP they will also do another small grinding job, thinning the crescent-shaped crankshaft thrust bearings.

The crank bearings are from a ZX10R.  The journal bearings are to be used unmodified but the thrust bearing is slightly too thick to fit into my crank design.  Instead of having a full-on special made, which is expensive and time consuming, I will have these stock bearings ground from the backside to the appropriate thickness.  Inexpensive and just as effective.  I'll have them grind matched sets in .0005 increments to allow me to dial in the desired crankshaft end float.

Coming up is the crankshaft rod journal machining.  Hopefully in a few days but you know how it goes!

Until next time,

Chris

It's déjà vu all over again

Seems like we were here a couple of months ago!
 
Once all the programming and fixturing is done making multiples is fast!  That's the beauty of sand casting and CNC.  Minimal material removal yet still a complex multifunctional part for a reasonable cost.  The first operation on the 3 new parts ran smoothly.  The crankshaft blanks nests nicely in the journal area.

Now I have to tear down the mill setup and reinstall the trunnion, dial it in, and run the remaining 4 axis programs.  If those run with no problems the two upper crankcase parts will be sent off to Millennium Plating for NSC plating and honing.  I'll send the J&E pistons with the castings so that Millennium can mic the actual pistons and get the piston to wall clearance dead accurate.

One task before plating is to finish machine and surface grind the stainless steel torque plate.  This will be bolted to each individual cylinder bank to simulate the head clamping forces during the final honing process.

When an engine is final assembled and you tighten the head bolts the cylinder walls distort slightly from round.  This is bad for piston ring seal so a the use of a torque plate simulates the distortion of clamping so that the cylinder wall is honed to a round shape in a condition close to actual running conditions.

That's all for now.  Hopefully I'll have the balance of the machining done sometime this week.

Final Casting Stretch

First off, apologies for the extended delay between posts.  This is a project that requires a lot of time which is not always available when trying to run a one man business in a recession!  In addition to client work that takes me away from time that could be better spent on this project I did manage to squeeze in a vacation riding dirt bikes in Moab, UT.  It was an absolute blast and a needed recharge away from the city.

As with everything these days some of the guys in on the trip did a blog site on it at ADV rider forums, appropriately titled 'Manhattan to Moab or City Blocks to Slickrocks'.  We got to ride some amazing terrain that is the antithesis of what I normally ride.  Grip levels on the rock were insane and the Slick Rock trail was like the biggest skateboard park in history.  The pics tell the story well.

Now on to more asphalt-based endeavors........

I received the final revision on the castings from Harmony.  This 1 lower and 2 uppers should be able to be used as parts for the first engine build.  The castings sown in the previous posts were casting samples that needed inspection windows and other machining features to allow verification of the internal features that precluded their use in a running engine assembly.  Now that the molds have been proven out and revised as necessary these parts should be the cases of engine serial number 000001 and the top of 00002.

The overall finish on the parts look excellent and soon more aluminum chips will fly.  Then its on to more crankshaft and primary drive gear machining then more parts then some more......

That's it for now.  Hopefully have another update soon,

Parts is parts

Just posting a few shots of the various parts that are accumulating.  It's nice to start a project like this and have spare parts available to experiment with.  Previous bike and engine projects have been one-offs and that presents a problem when failure is encountered- the need to wait for a replacement custom part, usually the weekend before a race!  Now we'll have the ability to have 2 complete engines plus a host of spare parts.  What luxury!

Most of the parts are produced to my specifications by the indicated vendor, the rest are standard aftermarket performance parts.  Thanks to Barry from Celtic Racing for referring us to Skip Dowling of Orient Express, a great source for all things OEM and aftermarket in the SportBike world.  Skip was able to get us the parts we need at very reasonable prices.  A shout also goes out to Fred Renz of Yoyodyne, a great resource for hard to get exotic parts and just about anything Brembo manufacturers, even the true GP equipment.


Castings:  a lot has been said about these parts and the great job Harmony/TPI is doing so I'll leave it at that.

Chassis Castings:  great parts from Harmony/TPI here too.

J&E Pistons:  producer of top quality pistons for motorsports.  These are a high compression version of their ZX6-R product.

Carrillo connecting rods:  What is there to say?  If you want the best rod, you buy a Carrillo.

Oil pump gerotor and custom drive gears:  fron Melling and SDP-SI, respectively.

Tungsten crank counterweights:  From Midwest Tungsten Service.  These bolt on counterweights that nest inside the con rod I beam area help keep crank and overall engine cases as narrow as possible.

Brembo front brake calipers and master cylinder from Yoyodyne:  Again, if you want the best, you get Brembo.

Ohlins TTX front damper from Motorsports Spares, who usually deal with 4 wheel vehicles, but had the knowledge of the generic Ohlins components to help us source a suitable solution for our front spring/damping needs.

Cometic gaskets:

Lots of misc bolts, seals, bearings, etc.

More misc parts, mostly from Orient Express:

I'm starting to amass quite a collection of parts.  Soon this chaotic jumble of parts will defy entropy and assemble into an organized machine capable of scorching the track.

That's all for now.

Flip-Flopping the Crankshaft

We've made good progress on the crank so far, one aluminum test part and 3 final steel parts all have the first lathe operation complete with no crashes, broken tools, or other mishaps.

Now we remove the 3 jaw chuck front he lathe and replace it with a 16C collet nose. The collet nose will allow us to hold the part very accurately from a previously machined feature.  We'll then indicate the length of the part and run the second lathe operation.  This operation creates the features for the generator main bearing journal, the front bank cam drive, and the tapered stator mount.


3 jaw chuck in first lathe operation:

16C collet nose for second operation:

Now just a few button presses and the 2nd operation is finished:

Repeatedly running the program finishes out the parts for now:

Now we are finished with the lathe work.  Next up will be putting the parts in the 4th axis on the mill and creating the 2 sets of offset throws for the connecting rods and the sprocket teeth for the cam chain drives.  once those features are complete I'll put the part up on a manual mill and drill and deburr the main and rod bearing oil holes.  Unfortunately, that will need to wait a week or so for some client work on the mill to be finished.

I Love CNC

The wonders of modern technology.

From:

To this:

In a couple of hours.  All the parts are accurate to within a few ten thousandths of an inch.

The switch from the 2024 aluminum test material to the 4340 steel part material required slowing the cutting speed by approximately  50% and increasing the feed rate by 25%.   It may seem counter intuitive to increase the feed rate for a stronger material but the carbide insert's cutting edge needs to be able to get a decent bite into the material, otherwise it just deflects the workpiece and rubs, causing a lot of heat buildup and usually insert/tool failure which leads to a scrapped part.

Now that all 3 initial pieces are machined I will change the setup in the lathe to flip the part around and accurately hold it by the features we just machined.  That post will be up soon.

Machining Step 1 on the Lathe

After a couple of long days and late nights machining non-motorcycle parts the lathe is open and I can run a test part of the first crankshaft program!  I'm making the first part from some scrap 2024 aluminum to verify the program before using the more expensive and much harder to machine 4340 steel material.

The machining process will be:

• drill 60 degree center in outer end for tailstock support
• roughing the main profile
• finishing the main profile
• machining small undercuts on main profile
• machine center main bearing fearure
• remove as much conrod journal stock as possible

This is what the setup in the lathe looks like.  As with the engine castings, we are at the limit of machine capacity but the part fits and that's all that matters.

This is taken after the finishing of the main profile:

And this is taken after the program is complete:

Here's some CAD vs reality for a comparison:

 The aluminum version looks nice but would never be able to withstand the temperature and stress of operation.  Next up is the 2nd machining operation that finishes the opposite end main bearing and tapered generator mount.  After that operation the part will move to the mill for some 4 axis work on the conrod journals and camdrive sprocket teeth.

Until the next update......

Programming Setup 1 on the Lathe

The first step in converting CAD to chips is to plan ahead, and it should happen very early in the design stages, otherwise you run the risk of having an unmachinable or hard to machine part.  What we are doing here is step 2, converting 3D CAD to 2D CAD to G-code CAM.  The 3D CAD provides complete surface information of the part.  Since at this stage the part is a simple revolved shape, we can reduce it to a 2D profile and not lose any information about the shape.  From this 2D profile the CAM software creates a series of 2 dimensional moves along the X axis (diameter) and Z axis (length of part) that create the part profile from solid bar using appropriate cutting speeds and feeds.

3D CAD:

2D CAD:

2D CAM:

Now we can go to the machine, which is currently busy.....

The CAM package is told the shape and position of the various tools needed to cut the part, it is told the shape of the part, and it is told the characteristics of the machine.  Doing what computers do well, crunch numbers, it uses all of this hopefully accurate information to calculate the appropriate motions to generate the desired part profile.  As with all computer programs, garbage in=garbage out, except instead of the BSOD or an inaccurate spreadsheet, you get twisted metal and a large repair bill.  It is a very good incentive to make sure all the info input is correct and also carefully check the output.  The output of this 2D CAM process is a text file in what machinists call a G-code format.  A sample g-code file in a format usable by my Siemens control looks like this:

%MPF52
G70 G90 G40 G54
(TOP-CAP-3-rec2-rad PR=3.745 Z1=8.075 )
(T-2 O-6)
(DCGX IN SDJCR-123)
T02 D06
G0 X0.825 Z.5
Z0.
M3 S1000
G96 S1000
M8
G1 X-0.0357 F.005
G0 X0.6316 Z.155
G96 S1500
G1 Z-2.99 F.008
X0.6864
G0 Z.11
X0.5567
G1 Z-2.4417
X0.5625 Z-2.4475
G3 X0.57 Z-2.4656 B.0256
G1 Z-2.99

The format is relatively simple and once you have used it a bit reading it is pretty straightforward.  The G-Code file is sent to the machine over the network and then after machine setup the program is run.

Once my current lathe job is complete the crank goes right in.  I hope to have another blog update sometime this week.

Starting on the Crankshaft

Now that the engine case patterns are approved and the production order placed I can move on to the crankshaft.

It will be a 180 crank to exploit the reduced variations in reflected crankshaft inertia that this configuration provides, similar to Yamaha's cross plane crank in the M1 Grand Prix bike and the R1 Super Bike.

I will be initially testing 2 different versions of the crank- one with pork chop counterweights and one with full circle counterweights. The main testing variable is the overall weight/inertia vs. aerodynamic efficiency of the 2 versions.

Full circle configuration:
Pork Chop configuration:


The manufacturing process will be as follows:

Material blank:

• 3 3/4" diameter x 9.7" long
  
• 4340 steel
• 28-32 Rockwell C hardness
  

In house:

• Machine crank on lathe in 2 steps blank leaving .01-.02 stock on surfaces to be ground.
• Mount lathe blank in mill 4th axis and rough machine crank throws
• Rough and finish machine the two silent chain cam drive sprockets with custom form end mill cutters.

Outsource:

• Hobbing of primary drive gear and starter clutch/crank sensor spline will be done by Eagle Machine, Inc. of British Columbia. They have experience to properly deail with custom low production crankshaft.
• Final Grinding of main and rod bearing surfaces will be done by Lopez Crank Shaft of Santa Fe, CA. They are another custom crank specialist and can provide the accuracy and surface finish needed.
• Plasma nitriding will be done by Accurate Ion Technologies, a specialist in steel hardening and advanced surface finishes. We are using plasma nitriding for it's low process temperature that enables proper multilayer surface hardening of the part with no distortion.
• Once we get the part back from Accurate Ion it is ready for use.
  

The process will involve 2 lathe setups and one milling setup.

The lathe first lathe setup will hold a 3 3/4" x 9.5" long material blank in a 3 jaw chuck. we'll machine one end of the crank, the middle main bearing journal, and various smaller features on one end of the part.

End of first lathe setup:

Once I finish some client lathe work currently running this is next in line. The next post will detail programming and cutting of this first lathe operation.

Long Block Assembly Shots

Now that we have a girdle, top, and a couple of heads the time is ripe for some assembly shots. I'll let the images speak for themselves...


Short Block:




Long block:



The overall engine assembly is very short front to rear to enable a long swingarm in a short wheelbase. The resultant slight additional height compared to a normal I4 is easily accommodated by the unique chassis needed for the Hossack-style front suspension.

Finishing the Girdle Machining

This blog post is dedicated to Chris Hodgson from San Jose BMW. I saw Chris and his crew at the BUB Bonneville motorcycle speed trial event last week while helping wrench for Scott Kolb on his 125cc partial streamliner. Scott set a new 2 way record of 146.7mph on the last day of the event after lots of tweaking. There's an article over at Hell For Leather on the effort. The trip was lots of fun, especially when a record is set. Every speed lover needs to go to Bonneville. It's only 2 hrs outside of Salt Lake City and besides having no speed limit also presents an awesome vista in any direction.



Back to the topic at hand, I had the short block with me for display purposes and Chris Hodgson was like 'when did you do that machining, the blog is not up to date, what are you waiting for!!!!!' Being chastised by an internet follower compelled me to get my ass back in gear. That fact that it was a person who is a world renowned BMW tuner made it go into high gear! Chris and crew also took a record with their BMW HP2 so it was a happy pit area all around.

Chris, this update is for you and hopefully I will be able to work on the project and update the blog regularly.

Now on to our regular programming...........

After the last post, which was machining the girdle split surface, we are up to the balance of machining on the girdle part. We were up to this point on the part:

Oil gasket and split surface machined:


The next step is to machine the girdle subplate then complete the part machining. The subplate screws to the oil pan surface and is accurately aligned to the trunnion table with dowel pins.



The first set of features to be machined is the crankshaft main bearing split surface:

Facing:


Drilling/tapping.......


Then the 4th axis is indexed 90 degrees and the clutch side is machined. there is a bunch of profiling for the cassette transmission side plate, trans and oil shaft bearing bores, gear clearance, and misc threaded holes.

Cassette mounting flange:

Gear clearance:


Roughing the bearing bores:


Once these deep bores and pockets are done the 4th gets rotated -180 degrees to machine the output sprocket side. The features on this side are the generator cover surface, oil filter mount, oil pump drive and pressure chambers, and starter bore. Yes, a starter motor! No rollers, no bumping, just press the magic button.


Facing gasket surfaces:

Some operations are pushing the limit of tool stability, like this 1" dia x 8" long insert end mill:


Starter motor mounting hole:

Gerotor porting:

The oil pump is a gerotor supplied by Melling, a high quality OEM/aftermarket automotive parts manufacturer. This style pump is highly efficient and compact when properly packaged. A lot of design assistance for the entire oil pump circuit was provided by Marc Goulet of Melling. Marc is also a motorcyclist and was kind enough to donate his time and put up with my unending questions on the subtle details of high performance oil system design. Marc has been involved in the design of some top level F1 engine oiling systems so he is definitely the person to ask in this field.

Inner and outer oil pump gerotor:


These parts fit into dual eccentric pockets that have CNC porting designed to allow high flow with minimal power losses.

Those 3 machining positions contain all of the high tolerance operations. Now on to some less critical ones:

Oil drain hole:


The position of the subplate is then indexed 90 degrees on the trunnion table and we machine the:

Upper engine mount:


Lower engine mount:


Starter mount:


That covers the majority of the machining on the girdle. Bearing bores will be finish machined as part of a complete crankcase assembly.

It ends up being one sweet looking part:




Stay tuned for more soon!