Large Journal Conrod Big-end EYE size please

[muskrat]

 G'day fellas, it's the reciprocating weight that you use your balance factor on. So a bal fac of 60% is 60% of recip weight (this includes piston,rings,pin & clips) + rotating weight. Make lead strip weights and wrap around b e journals, balance crank on knife edges as you would a wheel.
129g difference between the std and carillo is quite a bit when x 2 so would make a big difference to vibes.
Cheers

[Rocket Racer]

Thanks for that rocket racer, thats good info. I assume the weights include nuts bolts etc?

Yes, but I have not verified either of the weights provided to me.

Muskrat makes a good point the increases of either the new alloy or steel rods adds 140-218 grams to the crank and most modern pistons are also typically heavier than the original beesa ones so balance factor the next question, so I need to do some maths
Eddy Dow recommended increasing from 54% to 65% (for racing) in his "Twin Tips" and Paul Dunstall recommended a balance factor of 70% for the norton 650ss (for racing) , so quite a variation.

[duTch]

The money's come out of my bank, so I assume I have some Lightning-Thunder-rods, in transit or close to, so in about a week or so, I should be able to take them to my local health food shop and weigh them accordingly.
 Now,balancing is stuff I've had JS to do with?
       So my guess that to calculate the....'reciprocating weight'..
 

So a bal fac of 60% is 60% of recip weight (this includes piston,rings,pin & clips) + rotating weight. Make lead strip weights and wrap around b e journals

,
   ......is to maybe assemble all the aforementioned Muskie bits, and park the rig so the piston/rod L-e assembly bit is supported horizontally, and see what weight holds the crank/pin+big-end of rod horizontal, in same plane???(comprende ??) Tell me if that's wrong please?? or a better way.

     Also Steve said his Thunder rods have 3/8" bolts instead of 5/16", as said Pete (?) from Ridgecrest, which will explain a certain minimal amount of weight increase there.
      Just for reference, the BSA pistons I have are ~345-355grm and hepolite similar? can confirm that later if need be, how much difference does 10grm(for example) make?
    Hoo boy saturday(I think) night -things to do...
 Cheers for now, duTch

[muskrat]

 G'day Dutch,
                  I use two identical digital scales (200g x 0.1g cheap on ebay) big end on one little end on other. Don't forget to put the shells with the big end. Measure pistons separate and add to little end.
 Have a beer or ten for me, Working all weekend.
Cheers

[Rocket Racer]

A mate also pointed out to me that increases in piston/rod weight take the balance factor the wrong way, ie down. So in my case where I would like to increase the balance factor anyway, increasing the rod/piston weights is doing the opposite .

[duTch]

Thanks Muskr, got the amber sorted, and figured the scale thing, too bad you workin' all w/e and I 'm not- oh well someone has to carry the country..!
 I missed out adding into this bit....,

,
   ......is to maybe assemble all the aforementioned Muskie bits, and park the rig so the piston/rod L-e assembly bit is supported horizontally, and see what weight holds the crank/pin+big-end of rod horizontal, in same plane???(comprende ??) Tell me if that's wrong please?? or a better way.

.....-is with the rods bolted on the crank. So when weight distribution is determined, then adjusting the balance with the lead weight, but then what, weigh the lead and figure out where to drill/grind/add??
 Keeping in mind though that unless mine is way out of whack it's probably not going to matter much as I'm not racing(...well..um..?), but just be nice to know what exactly is going on down there, and how to rectify if need be.

Also RR, when you say 'piston/rod weight', I take it you mean top end of rod assembly(reciprocating), as compared to the other end(rotating), which means you want less loss of inertia type energy in reciprocation, and more rotational energy(power? torque?), balanced with 'lighter' crank for quicker get upn go?? ..Or something along those lines??
 wphew..heady stuff!!

cheers fer now

[chaterlea25]

Hi All,
Dutch,
Remember you will have to have the cutaways in the cylinder barrell widened for the new rods
Theres also some palaver about pre stretching the conrod bolts and or over tightening problems
There was a discussion on this topic previously????? Does anyone remamber where??
I have a set of MAP rods to fit to the RGS engine build, I think these have the same ARP bolts?

Cheers
John O R

[Rocket Racer]

Dutch,
 you're on the right track good interpretation, 10 points.
Always worth thinking about what increasing weight to components means. the top end of your rod and the piston change direction every time they get to the bottom and the top so light pistons and minimal reciprocating rod weight reduces load on your engine.
Every time you go up an oversize typically the piston wall gets thicker and the piston is heavier than that the motor was balanced for originally and when you add in heavy duty rods its rebalance time 
Cheers
Tim

[KiwiGF]

Hi Dutch, service sheet 712 has some info on balancing and where to drill holes (albeit the suggested location looks odd to me).

I'm also nearing the point of re-assembling my engine, but thought that as the SJ crank is -040 I was thinking of not getting it balanced, but after reading the other posts I'd also like to hijack the original post as well, as maybe a bit of home drilling is in order to get it closer to 54%.

2 x 18 oz is the figure in the service sheet given for standard % of reciprocating weight on the std A10, it seems to be the same for LJ and SJ cranks, 36 oz is 1020.564 grams. I'm not sure what BSA mean by reciprocating weight. Is it the total of rods/bolts/pistons/rings/pins?

If (and no doubt someone will correct me if this is wrong) the standard balance factor is 54% then the standard reciprocating weight works out to be (1020.564/0.54) = 1889.933 grams?

Does the reciprocating weight increase by 140 grams by using Lightning rods, to 2029.933 grams, if so, does this drop the balance factor to 50.2%?

By my calcs (using a density of a 10mmx5mm deep hole equates to 3.15grams so 140 grams at 54% would require 24 holes of that size, but actually more than 24 as they could not be all be positioned opposite the counter weight?  

24 is a lot of holes! (so I sort of hope its not 24).

[duTch]

Hiya Kiwi,
         I'll get back with more later, but for now have a look at Muskies and RR's earlier posts re:- reciprocating/rotating weights.
  36oz is 2,1/4 lbs -as you say 1020+ g that's a kilo....? 1/10th of the whole crank. You'd need a miners license for that- look out Gina! Bit of recalculating in order here??
 Be back after I analyzed the other stuff, and look at S/S 712, think I've looked at it it before
 Ciao fer now
   

[muskrat]

 G'day all,
             what I do after I have worked out the amount of lead I have to wrap around the crank pins and set up on balance beams. I use bluetak to stick bits of lead on the flywheel till I get a balance. Weigh the bits and drill the flywheel opposite to where they were stuck. A 1/2" hole 1" deep removes 0.80 oz of cast iron or 0.88 oz of steel. A 3/8" hole 1" deep removes 0.45oz ci or 0.50oz steel, a 1/4" hole 1" deep removes 0.21oz of ci or 0.23oz of steel. 1oz = 28.4g.
 I used 70% for the A7SS racer (but first took 2Lb off flywheel  ), 65% for the A10 cafe. Both a lot less vibes than the A65 (factor unknown).
A must do if foreign rods and os pistons are to be used.
Cheers

[duTch]

Thanks Musky I'll sleep on that one,
    Also John for the heads up re cutaways, and yes I'm fairly sure they have the same 'ARP' bolts.
Not sure about the other queries, re  discussion- stretching/overtightening.
 cheers for now

[Brian]

I used ARP bolts in my 61' A10.

I bought them from SRM but they recommended some ridiculous torque setting for them and would not reply to my e-mails when I queried it.

I ended up contacting ARP direct and had a few e-mails with their technical staff and in the end they recommended 28 Ft lbs. I went through the procedure of taking them up to the required torque twice before the third and final tightening. I used loctite on mine.

So far so good  

[KiwiGF]

Hi Dutch, I think my calcs above for recip weight based on the 36oz in service sheet 712 are incorrect, unless BSA had a different definition for reciprocating weight to what is generally used nowadays.  

Anyway, taking on board the comments on earlier posts I'm going to get some scales, weigh everything I'm using, and find out how to do the correct calculation, as it seems the billet rods in particular can have a big effect on the balance factor.  

[chaterlea25]

Hi Dutch and All,
Attached is a photo of the additional balance holes drilled in the crank of my RGS project
to accomodate the MAP conrods.
The crank has been dynamically balanced by SRM
The 2 holes nearest the flywheel bolt are approx 1/2in deep and the others app 1/4 deep
I'll leave you to figure out how much weight has been removed  ????

Theres a good reference to balance factors etc in "Tuning for Speed" 
no home should be without a copy LOL

Regards
John O R