Quote:
|
Originally Posted by MadMax
The usual failure point on a mechbox is at be the lower front corner of the cylinder window.
You could gain significant fatigue resistance by continuing the lower cylinder shelf forward just past the corner by about 0.1".
This would require a modified tappet plate with notch cutouts in the upright panel to pass the continued cyl' shelf, but the amount of material removal is probably not critical to the tappet plate. The strength of the remaining upright would probably significantly exceed the strength of the spaghetti rear arm which bears the sector cam triangle.
|
The std cast gear box molds are ages old and to be honest have been copied from the original. I don’t believe anyone that does gear box casting has thought to change the basic design. If they just changed the material from Zinc (yes they are zinc) to a more substantial metal such as aluminum we probably would not have the problem
Quote:
|
Originally Posted by MadMax
I'm guessing that your window corners are rounded as your mechbox is manufactured with a milling cutter. The rounding probably makes a greater contribution than polishing the exterior to reduce remove surface start cracks. Have you considered shot peening? I think shot peening would be a more easily applied surface treatment than polishing. The compressive prestress might also make a greater strength contribution than polishing.
|
No we don’t round the corners – several folks have asked but the design does not warrant that change. However, and you will find this in our design. At key points we have incorporated more material than required. This is so the owner can remove the material with a file to properly fit their selection of internal components. A prime example is the semi cut off lever. Depending on manufacture, these levers vary wildly in thickness. Our approach is t leave the boss for the lever long so you can file to fit your lever precisely. Rounding the corners would also fit into this category. If you would like to do it you can.
The gearbox is not polished in the senesce that it is polished to a mirror finish (although we do have folks in the NE that have done this. I guess you can call it a move from mil-sim to mil-bling) We do have a routine in th program that takes a finishing pass on key internal area to make sure thy are very clean. We don’t have any start or stop cracks in the finished box – again we are very delicate with the machining. We have not done shot penning although some models have been anodized black