Comparison of Saginaw 5699250 Flex Cplg Assy
I just finished a comparison of the 5699250 Saginaw drawings of the 1967 Corvette flexible coupling assembly to a recently available aftermarket flex coupling assembly from a Corvette supplier for the same application.
I really don't have any information as to where and how the aftermarket parts were obtained. My best guess would be that they took a Saginaw service flexible coupling assembly and had it copied.
There are five areas that I can see that are most likely not identical to the way that Saginaw manufactured the 5699250 flex coupling in 1967. There is another area that I cannot see that I am a bit more concerned and is really more critical than the cosmetic differences.
Let's start with the critical one first. You may have followed some of my previous rants were I expressed concerns about coupling bolts without shoulders. Most flex coupling rebuild "kits" have had common 3/8 and 5/16 bolts that merely squeeze the rubber. (All Saginaw OEM flex couplings have always had bolts that have shoulders to create a secure metal to metal connection.) With photographs of the aftermarket full assemblies you cannot determine if the two bolts are shoulder bolts or not. (I have concerns because the pictures of rebuild "kit" components from the same supplier clearly show common bolts.) You have to basically remove the bolts from a full assembly in order to determine if they are shoulder bolts or not.
We were pretty good at Saginaw with respect to updating flex coupling assemblies to use the latest design parts. This kept our component inventory lean and prevented potential mix ups with parts that were similar but not identical. However, this meant that the 5699250 flex coupling assembly sort of evolved and was upgraded from the original 1967 design through the years. The following are just observations that I can see in the photos of the aftermarket (AM) parts:
1. Bow tie flange - The AM flange has a cast rib that extends up the barrel of the flange. It extends up the barrel of the bow tie flange and is right next to the 12 point head of the pinch bolt. The rib was not added to the flange until 1975. In 1967 there was a small nub on top of the flange, located right in the same location as the rib.
2. Rivet heads - The Saginaw parts had a hot upset riveting operation that quickly heated the end to a cherry red color and squeezed the end of the stop pin. That operation formed a fairly smooth rounded head. It appears to me that the AM stop pins are deformed in a press operation in the cold condition. Not a big deal except that the heads on the AM parts would have sharp edges not found in the Saginaw parts.
3. Coupling disc - The Saginaw parts had 7 layers of neoprene rubber and cotton cloth. The layers of rubber were of the same thickness and equally spaced. The AM disc has noticeably thicker layers of rubber on the top and bottom exterior sides of the disc.
4. Stop pins - The original 1967 Saginaw flex coupling should have had short stop pins that were 0.63 inch long. The 5699250 assembly drawing was changed in late August 1967 to a pin that was 0.81 inch long (possibly a late 1967 model year change or a 1968 start of production change.) I can't tell the length of the stop pins that are used in the AM assembly.
5. Rubber Stop Pin Cap - I am pretty sure that the 5699250 assembly went into production with neoprene rubber stop pin caps. (They were added to the drawing in January 1966 which you might think would have made 1967 start of production in the fall of 1966.) The assembly drawing was changed in late March 1967 eliminating the caps. Now I don't know the effective date of the removal of the caps. The caps could have been eliminated as a 1968 start of production change or it could have been a running change during 1967 and the drawing was just being kept up to date.
All of the above changes were documented in the change block on the 5699250 flex coupling assembly drawing. So any service parts manufactured at Saginaw after 1967 would have had the longer 0.81 stop pins and probably no rubber caps. Service parts after February 1971 would not have had a ground strip (they would have incorporated a coupling disc with a screen molded into one face of the disc.) Assemblies manufactured 1975 and later would have had the rib on the barrel of the bow tie flange and not the nub.
It is possible that the NCRS studies of the 1967 & 1968 Corvettes may shed light as to when the stop pin lengths were increased from 0.61 inch to 0.81 inch. Also when were the stop pin caps eliminated? Running change during the 1967 model run, or at start of 1968 production?
Jim
I really don't have any information as to where and how the aftermarket parts were obtained. My best guess would be that they took a Saginaw service flexible coupling assembly and had it copied.
There are five areas that I can see that are most likely not identical to the way that Saginaw manufactured the 5699250 flex coupling in 1967. There is another area that I cannot see that I am a bit more concerned and is really more critical than the cosmetic differences.
Let's start with the critical one first. You may have followed some of my previous rants were I expressed concerns about coupling bolts without shoulders. Most flex coupling rebuild "kits" have had common 3/8 and 5/16 bolts that merely squeeze the rubber. (All Saginaw OEM flex couplings have always had bolts that have shoulders to create a secure metal to metal connection.) With photographs of the aftermarket full assemblies you cannot determine if the two bolts are shoulder bolts or not. (I have concerns because the pictures of rebuild "kit" components from the same supplier clearly show common bolts.) You have to basically remove the bolts from a full assembly in order to determine if they are shoulder bolts or not.
We were pretty good at Saginaw with respect to updating flex coupling assemblies to use the latest design parts. This kept our component inventory lean and prevented potential mix ups with parts that were similar but not identical. However, this meant that the 5699250 flex coupling assembly sort of evolved and was upgraded from the original 1967 design through the years. The following are just observations that I can see in the photos of the aftermarket (AM) parts:
1. Bow tie flange - The AM flange has a cast rib that extends up the barrel of the flange. It extends up the barrel of the bow tie flange and is right next to the 12 point head of the pinch bolt. The rib was not added to the flange until 1975. In 1967 there was a small nub on top of the flange, located right in the same location as the rib.
2. Rivet heads - The Saginaw parts had a hot upset riveting operation that quickly heated the end to a cherry red color and squeezed the end of the stop pin. That operation formed a fairly smooth rounded head. It appears to me that the AM stop pins are deformed in a press operation in the cold condition. Not a big deal except that the heads on the AM parts would have sharp edges not found in the Saginaw parts.
3. Coupling disc - The Saginaw parts had 7 layers of neoprene rubber and cotton cloth. The layers of rubber were of the same thickness and equally spaced. The AM disc has noticeably thicker layers of rubber on the top and bottom exterior sides of the disc.
4. Stop pins - The original 1967 Saginaw flex coupling should have had short stop pins that were 0.63 inch long. The 5699250 assembly drawing was changed in late August 1967 to a pin that was 0.81 inch long (possibly a late 1967 model year change or a 1968 start of production change.) I can't tell the length of the stop pins that are used in the AM assembly.
5. Rubber Stop Pin Cap - I am pretty sure that the 5699250 assembly went into production with neoprene rubber stop pin caps. (They were added to the drawing in January 1966 which you might think would have made 1967 start of production in the fall of 1966.) The assembly drawing was changed in late March 1967 eliminating the caps. Now I don't know the effective date of the removal of the caps. The caps could have been eliminated as a 1968 start of production change or it could have been a running change during 1967 and the drawing was just being kept up to date.
All of the above changes were documented in the change block on the 5699250 flex coupling assembly drawing. So any service parts manufactured at Saginaw after 1967 would have had the longer 0.81 stop pins and probably no rubber caps. Service parts after February 1971 would not have had a ground strip (they would have incorporated a coupling disc with a screen molded into one face of the disc.) Assemblies manufactured 1975 and later would have had the rib on the barrel of the bow tie flange and not the nub.
It is possible that the NCRS studies of the 1967 & 1968 Corvettes may shed light as to when the stop pin lengths were increased from 0.61 inch to 0.81 inch. Also when were the stop pin caps eliminated? Running change during the 1967 model run, or at start of 1968 production?
Jim
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