Wilsons Sandbox

On 4/11/2012 10:22 PM, beachmike1 wrote: > > Concerning the post on flywheel weight and vibration. With no counter > balancer a single is a seriously bad vibrator . This is due for the > simple view. > > First that if a rough approach to balance the piston at 100 % ( where > the counter weight is 100 % of the weight of the piston) the unbalance > of the up and down piston movement can be mostly accommodated and > cancelled out for about 25 degrees of each side of top dead. Enter and > bottom dead center. This is not perfect. The acceleration of the > piston is governed by the occulting influence of the rod throw ratio > and gereanl non perfect sinusoidal action against the pistons liberal > motions. The forces produced by the counterweight are perfectly > sinusoid auto in nature. > > The result is as follows. The piston motion is somewhat balanced by > the counter weight as stated. The crank however from about plus and > minus ten degrees on each side of THC to the same at BDC starts to > produce an uncompensated force creating vibration. This force is max > at plus ans minus ninety degrees from TDC. > > The dual counter balance system reduces this a lot but not perfectly. > First is reduces the overall vibration in the same way the counter > weight does. However by splitting the piston counterbalance mass into > two and turning them in opposite directions a good portion of the > vertical component of the piston forces are removed but instead of > inducing a single force with a maximum at plus or minus 90 degrees > from TDC these forces are split into two smaller forces acting in > equal and opposite directions canceling each other out. > > However again the action is not and cannot be perfect due to the > circular nature of the crank motion and the none perfect clocking of > piston forces with an additional issue with the piston forces not the > same at the top and bottom of the stroke. > > This is a common final project for third year mechanical engineering > student. Back many moons ago I wrote a program foe an HP 41 CV to run > this problem. It took fifty five lines of code for the simple counter > weight problem and another 35 lines to add the effect for the counter > balancer. It was in HP basic. In 1980. > > In about 1998 we hired an intern who when to the same school took the > same course and has the same teacher and was given the exact same > final exam. I was not happy. I did not help him on the work except > point out programming mistakes and help with prob > Em definition. I did go to the college to see why a prof would be so > lazy to do this and not correct the darn mistakes in the test to start > with. I was humbled when I found out this was such a pure test of > dynamics understanding that it was used to compare classes over the > years. And compare schools. > > A more interesting problem is to layout the second third and fourth > order evirbarations that gets ugly and requires a lot of programming. > > [Non-text portions of this message have been removed]

On 4/12/2012 10:04 AM, mark ward wrote: > > I was tempted to change everything over to minis, But desided I like > having everything a simple to Repair Or replace as posible on a trip. > > You can get regular size blade fuses Just about ANYWHERE, even an old > car sitting around. > Even someone passing by usualy has a spare, or can get by without the > Radio fuse etc. > > Small peice of tin foil or gum wraper in a real pinch. > > As with all my electronics, Camera (getting harder to find) GPS (hand > held) Flash light, "tent lanern, Etc Etc. I try hard to use AA's in > everything, so they interchange, when needed. > > I once used my GPS's lite to dig out the camera, to take the AA's > out and use them in the flash light, that was dead. (still needed the > GPS for anouther 1.5hrs) > > To replace to head light fuse at night, & no moon. > > [Non-text portions of this message have been removed] > > [Non-text portions of this message have been removed]

On 4/12/2012 10:04 AM, mark ward wrote: > > I was tempted to change everything over to minis, But desided I like > having everything a simple to Repair Or replace as posible on a trip. > > You can get regular size blade fuses Just about ANYWHERE, even an old > car sitting around. > Even someone passing by usualy has a spare, or can get by without the > Radio fuse etc. > > Small peice of tin foil or gum wraper in a real pinch. > > As with all my electronics, Camera (getting harder to find) GPS (hand > held) Flash light, "tent lanern, Etc Etc. I try hard to use AA's in > everything, so they interchange, when needed. > > I once used my GPS's lite to dig out the camera, to take the AA's > out and use them in the flash light, that was dead. (still needed the > GPS for anouther 1.5hrs) > > To replace to head light fuse at night, & no moon. > > [Non-text portions of this message have been removed] > > [Non-text portions of this message have been removed] [Non-text portions of this message have been removed]