Grind to balance parts?

Can't just drill and grind on pistons and rods w/o knowing where to do it best, please advise if you know.

I was grinding on the thickest part of the con rod bottom in the area marked. Kind of evenly around the corners, but I haven't a clue and it seemed to take a lot of grinding to take off any weight. The heavier one was definitely thicker than the lighter one in those areas.



Dave
69S

Depends on what you're trying to achieve. If its weight matching the heaviest rod/piston to the lightest you must have a 1 gram accurate scale. Avoid grinding any part of the piston. The reason is that unless the geometry and wall thickness is understood (and that varies from make to make) heat conduction, expansion and distortion will be altered. Never touch the alloy rod itself, only the steel end cap and remove equally on the outer circumference only, never in one spot. Personally I would recommend that both sets be taken to a auto recon shop and have the big ends re-sized and weight matched at the same time.

If you intend to reduce the overall weight of the reciprocating assembly, the balance on the crankshaft needs to be considered. All in all, for the time effort and risk of modifying existing components, you'd probably be financially and mentally better off seeing JS Motorsport about the issues.

Mick

I finally came to the conclusion that the JSM rods and pistons were most likely the way to go. Maybe if I sell my M1D Springfield, Ruger Super RedHawk and the S&W 63 this year, I'll break it down and do it.

Do they really give any more HP?

Dave
69S

I bought Jim's pistons for Ms Peel AND everything else non Norton Upgrade,
but darn it its still rewarding to get plain jane factory parts as optimized as possible and play like yesteryears real mechanics did. Piston can indeed be ground/drilled on, just ask Jim Schimdt, who I hope pipes up with more details in public.
Aim is to get within about 1/2 gram side to side to get running distinctly less noticed.

Steve, can you give me a general feel of how the JSM rods and pistons feel compared to the stock? I'm not worried about HP, just viagration (pun intended again).

Dave
69S

EXCUSE ME??

Mr DogT and any all readers - Ms Peel with rump rod + two helpers and crank dynamic balanced and pistons rods mass matched can not be understood here. Ms Peel has completely solved/conquered any and all faults and sensations of the Commando plus gained Insane Handling > with 3 more phases of power faster turns than any race video I'm studied for a decade now. Never found her limits in public so keeping list of tracks to visit. It does not take muscle to ride Peel as hard as you like, just good grip on bars and butt solid planted not to run out from under below 70 mph. Nothing but nothing gets to pilot but the tire surface interface reactions straight up spine to brain stem control center. Uncanny Flabbergastlingly Fabulous!!!

FLAT Disappeared from my sensation but for the shove of turbo fan smooth thrust and SEVERE corner G's no modern can handle. So you must go by JIm and the racers using them as Ms Peel's new engine is not yet installed. Only reason I got Jim's pistons was to get the CR she can tolerate because the lightened race Costworth pistons came out well over 11:1 w/o hogging out the small chambers.
Jim's pistons/rod are lighter still and caused a big headache by moving BF up into the mid 90's. But now thanks to Ken Canaga I can try 110% BF to see what that is like vibe wise and hook up wise.

I got plain Jane Trixie Combat to keep a toe hold on positive Earth Nortons and have something to discuss and share in common with others. Ms Peel is in whole 'nother orbit even w/o the blg block blown engine. Until a another rump rod Commando is fielded with a pilot that can break though straight steering limits phase two, its useless to discuss Peel performance and smoothness here. Even in phase two ordinary leaned steering Peel could leave any thing behind when ever leans were 45' or more. Again so smooth it was not wearing on pilot/me and everything I needed to sense got through but nothing else. You all and modern engineers just have no idea how much inter reaction commotion is going on that show up in one area but is really comming from another. I can die at any time so am being blunt and factual as I can for future joys of Commando'rs after my time.

Balancing rods end over end can be very tricky unless you have the proper equipment : http://www.precisionmeasure.com/fixt1a.htm
This means that unless you are intending to do quite a lot of this type of work, cost of the equipment needed means its not viable to use for one off jobs. Not really a lot to be gained from matching rod weights, without balancing end over end, so best option for building a well balanced race motor is to get the work done professionally. For road going machines unless appreciably higher RPM is to be used, or motor is mounted in a non rubber frame, then balancing work is not really required.

DogT said:

I finally came to the conclusion that the JSM rods and pistons were most likely the way to go. Maybe if I sell my M1D Springfield, Ruger Super RedHawk and the S&W 63 this year, I'll break it down and do it.

Do they really give any more HP?

Dave
69S

Click to expand...

Gotta keep the M1D!

I traded a ss SW 63 .357 with factory trigger job for Ms Peel head work. Sent in bolted under the head.

Jims Schimdt' $25 Norton Racing booklet covers lighening and balancing of factory crank, rods and pistons like no one else I know of, even drilled holes in pistons to recoil the nay sayers.

I use pellet drivers to make holes in things, machinery to shed walls. Also to cut limbs down, old pipes in half and rocks and roots in holes I'm digging. 12 ga and 308 best for these jobs. Sometimes I get tried of a rock knob in drive way so hand my friend and M14 and me a Garrand tanker M1 and knock it out. I like the pling but not the 8 rd clip in the vintage rifle.

[video]http://www.youtube.com/watch?v=fR1Ro3FQpqY[/video]

[video]http://www.youtube.com/watch?v=1onX3PlCfR8[/video]

I have a set of stock rods that were lightened but I haven't laid eyes on em for 30 years. They're still in an engine and yes they have been torture tested. All I can say is check for cracks then completely remove all casting marks, id lettering etc. and any nicks they may have gotten during rebuild or tear downs. Always sand along the length because you don't want to introduce any new lines or dips in their overall profile which will happen if you sand across the rod. They should be polished to a mirror finish which will show any dips or wows in the profile. There should be none. As I recall, if compared to stock, the squarish edge along the rods was rounded off noticeably on mine. Dog-T has it right on the caps but they can also be mirror polished. Norton caps don't have weight balancing blocks like v8 engines do so you can't do much else on them. The way the stock pistons were done was taking off material from the bottom of the deck on the inside. 1st you need to make sure your valve pockets are deep enough and if you equalize the cylinder volumes then one piston has to have the top of the deck taken down enough to equalize the volumes. Once this necessary work is done you can start equalizing the 2 components for weight.

Oh, No, I knew I shouldn't have mentioned guns in a Norton forum.

My S&W 63 is the .22 kit gun and the M1D has never been fired out of the armory, the Ruger 44 is a piece of $500 junk, my 1943 45 Colt 1911 shoots better, that one I'll never give up.

Dave
69S

I can't help thinking that it's a waste of time to worry about a few grams (or up to an ounce) difference in weight between the two rod/piston assemblies.

Apparently the reciprocating mass in a Commando engine runs to about 850 grams and if a balance factor of 60% is used then that leaves an unbalanced mass of 340 grams (12 ounces). If one rod/piston weighs an ounce more than the other, that's a little more than 8%. Yes, that will result in a rocking couple, but again it would only be about 8% of the magnitude of the rocking couple generated by a 180 deg twin of similar size (and 180 deg twins seem to be considered to be at least as smooth as 360 deg twins).

"Balance" is a misleading word to use in connection with a 360 deg twin, they're always going to be grotesquely unbalanced whatever you do, and against the seismic background redistributing a few grams probably isn't time well spent.

I love the story of the Scitsu 2-stroke triple racer. The guys who built it obviously had a very pragmatic approach when it came to balance. They built a 500 cc class GP race engine by adding a cylinder from a TZ250 to a TZ350 engine. A 120 deg crank was the right thing for a in-line triple, but the splines on the TZ crank components wouldn't allow that so they ended up with 131/131/98 deg firing intervals.

Cheers! ~ Gary

The Dreaded Ford 2 litre V4 , thew out the balance shaft on my last engine , gave it a nice ' lope ' and reduced flywheel made it the freeist running one Id had .
Putting in one miss matched pisto , bearings and crank from a motor F.O.R.D. literaklly ( found on rubbish dump ) was niether here nor there , at least unmeasureable .
Come to think of it , the motor it went in was handed to us at a rubbish dump too . Good value , these V 4s .

ANYWAY , it leads me to think that the best ' cylinder angle ' at the crankshaft for a ' parrallel ' V twin , is somewhere in the 100 to 110 deg range or thereabouts .

Bonnevilles ( 650 / 750 ) and Holden ( 186 / 202 ) were said to run freeer , pick up revs quicker in the smaller bore version . Though the larger bore provided more tourque for hauling freight .
Higher Compession providers greater B.M.E.P. thus greater efficency , but harsher running .= Bigger pressure cycle fluctuation .

The fluctuation has been prevalent in the thouhts the last few days . ROTATIONAL VELOCITY of the crankshaft is not REGULAR , or CONSTANT through the 360 OR 720 Deg of rotation between fireing intervals
on ONE cylinder .

The flywheel , amongst other things , provides the DAMPENING effect to the irregular motion or Rotation of the Crankshaft , this leads us to two things .

Vibration Damper & Cyclic forces .

Firstly the ' Vibration Dampner ' ! :shock: ?

Back in the Dynamo Days , before hanging alternators fixed to the end of the Crankshaft , an Eccentric Cam and Tensioning Spring was fitted , which removed the cyclic occilation at the SOURCE .
allowing the clutch to run at a constant rate per revolution .Giving long service intervals and limiting load irregularity and thus wear .

Brings us to the typical heath robinson one thing leads to another scenario.

The lack of a damper at the crank lead to it being fitted in the REAR HUB , so as all the bits between fluctuated and gear wear alledged to be caused by hardening issues ( That TOO ) occured .
Possibly resulted in improved standards of the unnessesarilly stressed components , but was bbolting the stable door after the horse had left .
IF the ' Cush drive ' was AT the CRANKSHAFT , the motion / rotation AFT would presumably be constant . So there room to screw more power through them if applied .

Next , to the iregular fire Crank , presumably the greatest force ( and thus greatest resultant motion ) applied is the ignition / power stroke ,
Somewhere in its duration is the period of maximum FORCE of rotation ( Tourque spike )
With a 360 Deg crank , thats once per revolution .
Now , if ' one ' applied one OVER the other , as in the manner of provideing the greatest continuous ' maximum force ' or perhaps the greatest rduction in fluctuation ( being what we are aiming for )
perhaps the 100 deg odd seperation / 200 , or is that 520 fireing interval will provide this .The equipment to verify or refine this assumption is available , at least theoritically ( computor model of forces )

On the other hand , ( how many do we have !? ) we have no true Torsional Dampener . Kieth Dukworth was preocupied with torsional dampening at the time he designed the Cosworth Twin .
One wonders if these were somewhat ' fine tuned ' in light of experiance in the Quantel version ??

So , its virtually unheard of NOT to have a Torsional Vibration Dampener , in a automotive engine of a considerable output , so as to lessen fluctuation in forces ( shock Loadings ) in the crankshaft .
Generally , within reason , Larger units are more efficent , to the point of neccesity . And apart from the fixed mass of the flywheel ? we have none .
That Apart , looking to utilise the accelerative forces generated En Mass , in a staggered fireing interval Crankshaft , can gretly reduce the non essential loads absorbe ( blowing the crank vcase apart )
if they are contained in and transmitted as output in the rotational plane of the crankshaft .

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Now if thats a bit vauge or etheric , having things a bit out of whack , doesnt nessecarily cause problems , its likely too . 50 % odds its hindering rather than assisting continuous motion .
and the magnitude of amplification . ( read several tons imballance ) at Max r.p.m.s are why a proceedure of minimiseing losses in a given design is going to provide significant improvements
both in output and tractability .

Further , the Force generated BY the CENTRALLY placed flywheel is fundamental to the dynamics of most British Twins .
Having the mass distributed along the crankshaft ( as in say a four ) reduces the ability of the mass to change course , due to gyroscopic procesion . Thus the renowned manouvreability
of the Classic British Twin ( umless it was a Triumph built before 1970 which tended to manouvre as it saw fit , unless firmly applied power pinned it on course, with no bumps :shock: )

So this bloke worries that certain young typkes are takeing development currently up the wrong stream , diverting from the source through being blinded by science and modern design criteria .
Excuse the tirade / discourse , somell be getting used to em , intention is to convey conclusions of much contemplation of causes ande effects .Removeal of non essential elements being at the
core of most design . In the Era of their Prime , at least .

Now if thats a bit vauge or etheric , having things a bit out of whack , doesnt nessecarily cause problems , its likely too . 50 % odds its hindering rather than assisting continuous motion .
and the magnitude of amplification . ( read several tons imballance ) at Max r.p.m.s are why a proceedure of minimiseing losses in a given design is going to provide significant improvements
both in output and tractability .

Further , the Force generated BY the CENTRALLY placed flywheel is fundamental to the dynamics of most British Twins .
Having the mass distributed along the crankshaft ( as in say a four ) reduces the ability of the mass to change course , due to gyroscopic procesion . Thus the renowned manouvreability
of the Classic British Twin ( umless it was a Triumph built before 1970 which tended to manouvre as it saw fit , unless firmly applied power pinned it on course, with no bumps :shock: )

So this bloke worries that certain young typkes are takeing development currently up the wrong stream , diverting from the source through being blinded by science and modern design criteria .
Excuse the tirade / discourse , somell be getting used to em , intention is to convey conclusions of much contemplation of causes ande effects .Removeal of non essential elements being at the
core of most design . In the Era of their Prime , at least .

Click to expand...

Thanks for making so much sense to me here. Putting the narrow gyroscope down low and up front help bike fling this way or that. Getting the side to side imbalance minimized helps the pilot hang on easier while the firing order pleases the rear patch power pulse hook up on edges. Rubber damper in drive train is mere after thought in BI as the shafts bending and twisting do about as much to take up the hits delivered to the pilot and tire. I am in agreement that last few decades of modern cycle designs are being misled by tire improvement and rigid construction dead ends, literally. I'm now shooting for flexy in the middle, stiff at the tips to let the isolastic power unit dampen the traction spikes from jerky crank motion.

BTW Jim just sells us his off the shelf light pistons/rods as is, while at home he makes his pistons set lighter yet by the his traditional holey path. Don't know what he does for increased balance factor if anything.

It' pity Stanley Unwin isn't still with us.