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Tech Information => Technical Discussion => Topic started by: wobblywalrus on January 15, 2018, 10:41:35 PM

Title: Motorcycle crankcase expert needed
Post by: wobblywalrus on January 15, 2018, 10:41:35 PM
These case halves are held together by bolts.  It takes far less torque to remove them than to install them.  Shiny areas on the mating surfaces indicate the halves may be rubbing against each other.

What I want to do is send these halves to the one of the best experts we have in this country to get an opinion about what to do.  Any recommendations on who this might be?
Title: Re: Motorcycle crankcase expert needed
Post by: John Burk on January 16, 2018, 12:24:45 AM
Up the bolt/stud size for more clamping pressure .

Tom Evans , motorcycle inspector would know .
Title: Re: Motorcycle crankcase expert needed
Post by: Buamotorsport on January 16, 2018, 12:39:09 AM
Can I suggest Larry McBride the drag racer. I have his contact detail if you want them.

But first look....what are they from? If it’s Honda, Kawasaki, etc then you could try to increase the bolt size but, be very careful as there doesn’t seem to be much metal around the stud/bolt holes.

Talk to Larry he builds his own motors and can hopefully give you guidance.
Title: Re: Motorcycle crankcase expert needed
Post by: maj on January 16, 2018, 06:29:25 AM
Bo on the Suzukis we use studs with higher torque values , but the catch is stud diameter can interfere with the case alignment  (oversize the non threaded half )
and extra tension can change the shape of the bearing bore (rehone)
Title: Re: Motorcycle crankcase expert needed
Post by: ggl205 on January 16, 2018, 08:37:37 AM
I am no MC engine expert but main saddle bolt holes appear to be sleeved. Those should keep main bearings located even if case halves squirm a bit. If you want to keep both case halves from moving but don't change bolt diameters, I would try putting a few more locating/retaining dowels around the case where there is sufficient material to do so.

John
Title: Re: Motorcycle crankcase expert needed
Post by: TheBaron on January 16, 2018, 12:03:33 PM
A few things to consider:

Are all the "Dowels" snug in their bores and inplace?

Are there "Hard" washers under the Nuts and Bolt heads And are you lubing them? If the fasteners turn against the  aluminum you will have issues.

Are you retorquing the case fasteners after  a few heat cycles on the engine.

Short fasteners  do not hold their settings as well as long studs and bolts and often need retorquing (fasteners are springs in tension after all).

Robert in Costa Mesa
Title: Re: Motorcycle crankcase expert needed
Post by: wfojohn on January 16, 2018, 12:35:19 PM
Helicoil the bolt holes so you are pulling steel to steel instead of steel to aluminium and retorque after each of the first 2 heat cycles.
Title: Re: Motorcycle crankcase expert needed
Post by: edinlr on January 16, 2018, 02:32:33 PM
When I talked to ARP about making studs for my CX Hondas, they said first that they did not have any that would fit.  When I inquired about having them made, their response was that there was not enough depth for the studs to grab to do their job.  New bolts were not offered up based on the same theory.  At this point a perfect Helicoil seems the only option when there are issues. 

Are you having problems with the cases, or just concerned about the contact?  Most, if not all of the big four cylinder Jap bikes split their cases this way and this isn't usually a problem area.  If you did any machining to match the cases then you to line bore the cases and probably have other issues develop too.  Unless you are having a problem I'm not sure I would worry about it to much.
Title: Re: Motorcycle crankcase expert needed
Post by: wobblywalrus on January 17, 2018, 12:41:47 AM
The bolts were tightened to 10 Nm and then 75 degrees of turn was added.  These are 1.5 mm pitch threads.  75/360 X 1.5 = 0.31 mm  The added turn gave 0.31mm more stretch.  Removing the bolts took about 10 Nm.  It appears the 0.31 stretch disappeared.  Either the bolts stretched or the crankcase deformed.

This is what I know about the cases.  They were made by SKF, they are die cast, and they are "LM2 to JVM Specifications."  The typical alloy for this die casting is A380 with a 23 ksi yield strength.  The area under the bolt head is 0.299 inches.  Yield occurs in the aluminum under the bolt head at:

23 ksi x 0.299 sqin = 6.88 kips tension to cause yield in the aluminum under the bolt head.  Tomorrow I will look at the tension to cause thread pullout.
Title: Re: Motorcycle crankcase expert needed
Post by: salt27 on January 17, 2018, 01:44:02 AM
Bo, I assume that there is some sort of gasket involved?

  Don
Title: Re: Motorcycle crankcase expert needed
Post by: TheBaron on January 17, 2018, 09:55:38 AM
"Good Grief Charlie Brown!"    you are trying to stretch a case fastener .012" of an inch (.31mm)

Does not this sound like a bit much ?

Moving the decimal point one place to .0012"  seems more in line to me....

TRD had us using the "Torque then Turn (so many degrees)" method when assembling the all alloy Champ Car V-8 motors back in 1997 when I was there. There was no gasket, only sealer on the castings.

I hated doing it as it just crushed and deformed things all over the place. Aluminum is so soft and uneven in hardness that you are almost guaranteed to crush into it with this method....
 
I overhauled many Continental and Lycoming 4 and 6 cylinder aircraft engines and a few Pratt and Whitney radial engines back in the 70's. They all used the same method on the crankcase thru-studs,,,, Lube the threads as directed, torque them down in the order specified to the value specified, and use a freshly calibrated torque wrench! No Issues ever .

my 2 cents........

Smitty

Title: Re: Motorcycle crankcase expert needed
Post by: wobblywalrus on January 17, 2018, 10:34:25 AM
That is why I posted it.  These might be "torque to yield" fasteners where the bolt is under plastic deformation.  The cases and where the head of the bolt seats do not appear to be distorted.  Some late night calcs showed that a bolt with less than 71ksi steel would stretch before it distorted the seat.  There is no gasket.   
Title: Re: Motorcycle crankcase expert needed
Post by: TheBaron on January 17, 2018, 12:22:04 PM
If they are "torque to yield"  fasteners then one-time use would be mandatory,,,, is that spelled out anywhere in your service specs?



Title: Re: Motorcycle crankcase expert needed
Post by: Interested Observer on January 17, 2018, 02:20:39 PM
Scaling the geometry of the bolts from the photo in reply #3004 of the Go Dog thread, and unlimbering the electronic sliderule, we find that the 40 Nm makeup would produce 5,841 lb force per bolt assuming a friction coefficient of 0.12 in the (loctited) threads and 0.08 at the underhead surface.  This makes a longitudinal stress of 51,500 psi in the large diameter shank and 73,540 psi in the smaller shank.  The breakout/make-up ratio is 0.289, so since the 40Nm makeup is about 30 lb-ft, the reported 10 lb-ft breakout is to be expected.

For the second make-up method, 10 Nm followed by 75 degrees of rotation, we get a total of 13,523 lb force per bolt and stresses of 119,235 and 170261 psi ASSUMING WE ARE STILL IN THE ELASTIC RANGE OF THE BOLT MATERIAL.  Which we probably are not.  If not, these numbers would be lower, to be determined by the stress-strain curve of the material.  The breakout/make-up ratio remains the same but would depend on the actual final achieved preload.

Take a bolt to the local Instron machine and find out what it does.
Title: Re: Motorcycle crankcase expert needed
Post by: wobblywalrus on January 18, 2018, 08:29:56 PM
Triumph does not advise against bolt reuse.  Tonight the main bearing clearances will be checked and I will check a few bolts for permanent deformation.  They need to be installed and removed to check the clearances.

The ARP catalog, pages 21 and 22 give instructions for ordering custom studs or bolts.  Triumph does advise against using more torque or turn than specified.  They say the engine will be tight and have premature wear.  A phrase I am considering for the work order is "The new bolts should provide installed clamping force similar to the bolts used now.  The objective is for them to maintain this clamping force after use."   
Title: Re: Motorcycle crankcase expert needed
Post by: WhizzbangK.C. on January 18, 2018, 08:45:29 PM
Just a thought that entered my mind, probably not directly applicable to this situation but somewhat related. The cylinder studs on Volkswagen air cooled engines used a thick washer under the nut against the cylinder head. I have no idea what this washer was made of, but from experience I found out that substituting a steel one in its place would result in pulled threads in the case, especially on big bore high compression builds. I never had an issue as long as the correct washers were used, but pulled several when wrong ones were installed. My working theory at the time was that the washers were a special alloy that worked as a kind of spring to compensate for cylinder growth under operating heat and maintain more or less consistent tension on the studs.
Title: Re: Motorcycle crankcase expert needed
Post by: Interested Observer on January 19, 2018, 09:07:22 AM
Quote
The objective is for them to maintain this clamping force after use.

Wobbly, what makes you think the bolts “lose” their preload capacity just because they have been slightly stretched?  Just because they may have been somewhat “yielded” doesn’t mean they have lost strength or load capacity.  They may have gotten longer but are still carrying the load that caused them to get longer.

The “yield point” of ductile materials is generally obtained during tensile testing at a point of 0.2% of plastic offset--that is, the material has already undergone some “set” just to obtain that basic information.  When the test is continued, the specimen will continue to carry more and more load at much greater amounts of strain, and the ultimate strength is always greater than the “yield” strength.

The 0.31 mm elongation added to the bolt by the 75 degree turn amounts to only 0.4% strain--just barely(0.2%) past the minimal amount used to determine the yield point.

Consider:
1)  That’s what Triumph says to do.
2)  When you do that, with the bolt loaded up to that degree, both they and you are satisfied.  The bolt is supporting the desired load in a slightly yielded form.
3)  Removing the bolt won’t alter its form.
4)  Reinstalling the bolt returns it to the same load condition that it was satisfactorily sustaining previously--so what’s the problem?

Based on the two make-up methods it seems that Triumph are shooting for about 6000 lb preload for the bolts and are using something like 75 ksi yield material to limit it to that neighborhood but insure that it is at least there with the 75 degree turn method.
Title: Re: Motorcycle crankcase expert needed
Post by: manta22 on January 19, 2018, 10:10:42 AM
Whizzbang;

Could those special washers be Belleville washers?

Regards, Neil  Tucson, AZ
Title: Re: Motorcycle crankcase expert needed
Post by: WhizzbangK.C. on January 19, 2018, 07:59:12 PM
Whizzbang;

Could those special washers be Belleville washers?

Regards, Neil  Tucson, AZ

No, not Belleville type, no cup to them at all. Visually they appeared to be just a thick flat washer, but as I recall they weren't steel. More like a brass or bronze type alloy IIRC. It's been over 30 years so my memory may be just a bit vague.  :cheers:
Title: Re: Motorcycle crankcase expert needed
Post by: wobblywalrus on January 19, 2018, 09:14:36 PM
The bolts are losing clamping force.  Case separation results in lubrication failure to critical parts with drastic and sudden bad results at the worst possible time.  This problem is not uncommon to hopped up jap bikes.  The big plan continually changes while I learn more and get advice.

The current plan is to torque down the standard Triumph bolts as recommended by them and to measure the ID of the crank journal shell housings without the shells.  Studs or bolts made by ARP to their recommendations will be installed to their torque values.  Then I will check the housing diameters and contact them for advice if there are any problems.

The ARP folks deal with this stuff on a daily basis.  I do not have a clue.  This seems like a good approach to the issue.
Title: Re: Motorcycle crankcase expert needed
Post by: wobblywalrus on January 20, 2018, 03:36:51 PM
A call was made to the fellow who runs and develops the bikes for the Triumph race team.  The manual says to initially tighten all bottom case bolts to 10Nm then flip the engine over and tighten the top bolts to 10Nm before proceeding to the final tighter torque values.

The additional step he recommends to to repeat this first step at 10Nm until there is no movement in any bolts before proceeding to the higher torque values.  He said this should fix my problem.  I did this and it does result in more degrees of turn on those big retaining bolts to get to 10Nm before the final 75 degrees of turn.

Uncoated rod bearing shells should work just fine, he says, and they run there engines up to 10,000 rpm.  My rod bearing problem might be caused by oil pressure loss when the cases separate and it might disappear when the cases are torqued down tighter.  Uncoated rod bearings will be tried this year along with standard Triumph case bolts.       
Title: Re: Motorcycle crankcase expert needed
Post by: edinlr on January 29, 2018, 11:43:14 AM
http://www.cyclexchange.net/Machine%20Work%20&%20Services.htm

Here's a link for Cycle Exchange.  They mainly work on old Honda 4s.  They have some discussion down to the middle of the page about crankcase alignment and even determining when you have torques the case too tight and are binding the crank.  They do some work to correct this.
Title: Re: Motorcycle crankcase expert needed
Post by: Vinsky on January 29, 2018, 01:45:00 PM
ARP has a recommended torque chart and also an assembly lube recommended on the bolts for the correct torque values.
http://img.photobucket.com/albums/1003/SCHWARZERM/Car%20Technical/ARP_TORQUE.jpg?hotlinkfix=1517251304858
Title: Re: Motorcycle crankcase expert needed
Post by: CNC-Dude on February 02, 2018, 04:53:58 PM
The bolts are losing clamping force.  Case separation results in lubrication failure to critical parts with drastic and sudden bad results at the worst possible time.  This problem is not uncommon to hopped up jap bikes.  The big plan continually changes while I learn more and get advice.

The current plan is to torque down the standard Triumph bolts as recommended by them and to measure the ID of the crank journal shell housings without the shells.  Studs or bolts made by ARP to their recommendations will be installed to their torque values.  Then I will check the housing diameters and contact them for advice if there are any problems.

The ARP folks deal with this stuff on a daily basis.  I do not have a clue.  This seems like a good approach to the issue.

It more than likely will make the housing bores smaller when switching to ARP fasteners because of their higher torque requirements. This is also common in automotive engines when switching from OEM bolts to ARP studs as well. You will often need to hone the housing bores larger to get them back in spec. But also will allow you to go slightly to the high side of the specs to get you the extra few tenths of clearance you were needing.
Title: Re: Motorcycle crankcase expert needed
Post by: wobblywalrus on February 02, 2018, 11:09:19 PM
Triumph made two crankcase bolt modifications.  I did the first modification a few years ago.  This year the second one will be tried with the bolt torque procedure I learned from the Triumph flat track bike tuner.  New bolts of the latest style will be used.  This concept works OK on the flat track bikes and they rev to over 10,000 rpm.  Mine rev limiter is at 9,000 so their method is likely to fix the problem.

The crank shells I bought were early model ones.  The shell part number changed but the dimensions appear to be identical.  The numbers stamped on old and new style shells are different.  The shell manufacturer website says the new model shells have a more durable surfacing based on those stamped numbers.  New model shells are on order and should arrive in mid February.  Thriumph parts are expensive and they take a long time to get.

Crank bearing clearances in the past were set to values recommended by Mr Mc Knight of Mahle which are 0.00075 to 0.001 inches per inch crank diameter with an extra 0.0005 clearance for racing.  This is 0.0016 to 0.0020 for the crank.  Triumph recommends 0.0007 to 0.0017  Mine are at 0.0015  This is OK by my thinking.  The clearance will increase when the aluminum crankcases warm up and it should be right in the middle of Mahle's clearance range at operating temperature.

Crank shells are the largest I can get and there is not enough clearance between them and the crank for polymer coating.   New cases cost $3900 on Bike Bandit so I hesitate to do any modifications to the ones I have unless I run out of alternatives.

The rod big end shells are Triumph ones.  They are used on hopped-up rocket 3's with 80 HP per cylinder and 767 cc cylinders.  My engine has 500 cc cylinders with 53.5 HP per cyl.  The big end shells should be good enough.  Mahle's recommended clearance is 0.0017 to 0.0021.  Mine are at 0.002 so they should be OK.  These are steel rods on a steel crank so clearances are not expected to increase much when the engine warms up.

An article on engine building I am reading says that good crush is needed to get adequate heat transfer from the shell to the rod and from the shell to the crankcase.  Honing the rods or cases might be problematic if too much crush is lost and heat transfer becomes an issue.  Uncoated shells in standard size bores will be used for now.  I lack the tools and skill to evaluate and measure both bores and crush.

This engine building is sorta mental.  It does not come naturally to WW.