I got the crankshaft in from Canada a few weeks back and have been busy ever since trying to make it fit the rest of the engine ( read drive belt pulley ). The maker claimed that his balancers would not be able to finish it in several months so I had him send me the crank in “unbalanced” condition.
As this was a Triumph T140 crankshaft from the beginning, with crankpins sitting in line, it has been cut into two pieces and welded on to a new centre flywheel – with the crankpins staggered by 90 degrees. Read under IGNITION on this site and you will see why I have chosen the 90 degree offset. The man has done a nice job and the whole thing looks promising. However, I am now left with modifying the drive side to fit the pulley, which of course includes making a completely new pulley, plus trying to get the crank in static and dynamic balance. The maker supplied the crank, a couple of loose counterweights and balancing instructions that have taken me 4 weeks to de-cipher as they were not quite correct to put it nicely. Below is the unit on a couple of wood blocks, resting on the drive and timing side bearing journals.
As it looks now this thing is in serious un-balance. First we have to determine how much weight to attach to the crankpins to simulate the weight of the connecting rods, pistons, piston pins, rings and circlips plus the lubrication oil that will fill the cavities to be pressed out, through the holes you can see in the journals, to lubricate the big end bearings. The method is straightforward. I had to measure the weight of the big and small end of the connecting rods plus the total weight of the piston with rings, pin and circlips. Now I have to make bob-weights, to be attached to the journals, and their weight shall be the same as the sum of the connecting rod big end weight, plus the weight of the oil, plus the weight of all the other components multiplied by the so called “balance factor”.
The “balance factor” is the trick to the whole thing. The size of the factor determines how much and at which rpm´s the engine will vibrate. That it will vibrate is beyond all doubt, the question is only how much and at which engine speeds. In my case I have been recommended to choose a factor of 40%, as that is supposed to produce minimum vibes at 6000rpm and up through the 8500 that I see as the red line for this motor. Below is one bob-weight on the precision scale. In my case, each one of these shall weigh exactly 500grams.
Below is the crankshaft with bob-weights attached to the crankpins with Ty-Raps. The bolts and nuts are there to bring the weight to the exact 500 grams. In the top left and bottom right corners you can also see the counterweights, here held in place by pliers. This was just to check whether I was on the right track or not. Tomorrow they will be welded on to the flywheel and then all of brought to the balancer. Let us see if he can bring the whole thing in order. First we are seeking the unit to be in static balance. This means that regardless in which position I place the crankshaft it will stay there. No part being heavier than the other in other words. Then follows the dynamic balance, which is to make sure that at both main bearing locations there will be no upwards/downwards-acting forces when the crankshaft is rotated. I am all excited and wonder if this will work. If it doen´s, who can I put the blame on??
In the front below is the Weslake/NRE crankshaft that goues into the engine I was originally going to use. You can compare the sizes of them both. The Triumph/Norton crankshaft weighs in at 7500 grams while the Weslake/NRE in front weighs 10,800 grams. A lightweight Steve Maney crank weighs in at 7700-8100 so we are a bit better off.
While at it today I took a couple of shots of the rest of the engine. Below shows the camshaft acting on the tappets that run in tappet blocks that are held in place by the set screws in front.
And here the rtight side engine block with cylinder installed and the camshaft drive line. This is a heavy-duty German chain from IWIS. Supposedly the best thing since sliced bread.