Hello John Regan: This cover has a closed tensioner boss with a tapped hole
Is this identical to the earlier version with exceptions of these threads and the "B" suffix? I'm needing to furnish one of these for my 09 project....any comments/questions much appreciated.
Can one of you gentlemen tell me what this correct spring hole diameter and hole depth are please?
I can guess at this from Mark Herdman's photo, but am assuming that spring performance is dependent on these accurate dimensions. Also curious whether this correct spring was used elsewhere on the early chassis?
Scott, the cover with the small numbers is original, I think the one with the big part number is also, but I'm not as sure about that one.
Many thanks for this info. We'll use the .77 depth and then have room to open it up if more required. I will be using John Regan's repro spring with this, so very appreciative to have these confirmed numbers.
I think more critical to proper function is vertical measurement from the center of the fan arm hole to the bottom of the pocket as measured pocket depth on a reproduction could be correct, but placement of the boss incorrect.
In my possession I have what is supposed to be one of the "correct" reproduction 1910 covers using a spring. The spring pocket is finished with a drill bit, so depth is subjective based on where you measure it. From its deepest point in the center it is 0.790 and at the outside edge it is 0.660. My guess is the spring pocket in an original is flat bottomed.
Using a depth of 0.800, since that's between what Kim measured on the two shown above, I get that the distance from the center of the fan arm hole to the bottom of the pocket is 1.098.
Many thanks Walter...will confirm this 1.098 dimension as the hole is bored. Could be an equally relevant dimension from top of the spring boss to the same center of fan arm. Much appreciation if you can provide this dimension from your cover.
From the top of the spring boss to the center of the fan arm hole is 0.298, so call it 0.300. That could be used to judge relation, but really shouldn't be a datum point. What would be ideal is if Kim could measure his original and also confirm how the bottom of the spring pocket is finished.
Just going by your photos, my guess is you have a cover intended for a spring that somebody plugged and tapped for a bolt. You look to have a clean counterbore at the top as though the plug is pressed in below-flush. Does it measure 0.627 diameter like Kim's? My reproduction is the same.
I should think this bore depth could be fairly flexible without perform issues....say +/- .13.
I also agree that a flat bottom bore versus drill point is desirable here. Not that I think performance would be impacted...just amounts to good design practice. I see where Mark Herdman's original clearly has this flat bottom.