barry68v10 wrote on 04/12/08 at 15:43:40:Not quite the direction I was going...I like radial tires...but I like cast iron engine blocks...for street/intermittent use drums are a better design than disks, but for track/continuous use applications or submerged operation, disks are better. For a recreational offroad truck, or for heavy hauling, it's still tough to beat a solid axle/leaf spring setup for cost vs. function.
Don't get me wrong, I'm not AGAINST change or new technology, just against change for the sake of change or more commonly, for simple marketing.
KwakNut, I'm willing to change my mind here...So, what about the OHC design makes it superior for any and all applications?
What do you gain with OHC vs. pushrods? Are there any drawbacks?
Okay, here's my two penneth:
OCH vs PushrodAdvantages of OHC:
- Less moving parts/valvetrain momentum to sap power
- Capacity to rev higher
- More precise timing control without pushrod flex and elastic ‘lag’ in long valvetrain
- Port shape can be optimised without having to make space for pushrods
- Often (though not with Savage design) no need for rockers
- OHC designs allow easily for 4-valve setups which increase power without sacrificing torque compared with 2-valve heads
Disadvantages of OHC:
- Don’t have nice shiny chromed pushrod tubes on the outside of the barrel
- Taller engine
- Pushrod setup is cheaper in a vee engine
- Can be more difficult to set up timing than a pushrod motor
Disks VS DrumsAdvantages of disks:
Resistance to heat fade
Better cooling from better surface area
Stronger braking weight for weight
Self-drying after puddles/wet weather
Less unsprung mass than drums
Easier to access/maintain
No trapping of dust to clog mechanism
Braking not affected by drum expansion
Don’t require adjustment or self-adjustment mechanisms
Disadvantages of disks:
Rotor size limited by wheel diameter
Not as good static (ie for parking) as drums