gramps1951 Posted August 23, 2020 Report Share Posted August 23, 2020 the rear frame section on my 1951 b3b is a little thin in spots. I have seen boxed frames has anyone ever seen where frame rails from the same truck where you took lets say the right side of a donor rail was welded onto left side rail in a overlap style changing a c shape to a box shape frame rail where it would now be twice as strong. I have never seen this just a thought. Has this been seen? What do you think? Thanks Neil Quote Link to comment Share on other sites More sharing options...
gramps1951 Posted August 23, 2020 Author Report Share Posted August 23, 2020 you would do both sides of the truck to match. Quote Link to comment Share on other sites More sharing options...
DJ194950 Posted August 23, 2020 Report Share Posted August 23, 2020 Gramps- Do you haul big loads in the bed? DJ Quote Link to comment Share on other sites More sharing options...
Los_Control Posted August 23, 2020 Report Share Posted August 23, 2020 depends, what motor and trans do you plan to run? The little flat sixes may only have 100 hp, they are known to be torque monsters and twist frames in 1/2. If you have rust issues maybe just repair them? Quote Link to comment Share on other sites More sharing options...
gramps1951 Posted August 23, 2020 Author Report Share Posted August 23, 2020 no heavy loads and only 258 6cyl . no I don't need super strong frame just wondered if anyone had seen it done seems it would be very strong. finding rear solid frame rails would not be easy to find I would think. Quote Link to comment Share on other sites More sharing options...
Jerry Roberts Posted August 23, 2020 Report Share Posted August 23, 2020 As a side note ; The Ford model T ' s were designed to flex ... a lot . That flex allowed them go through such rough terrain , the frame would just twist like crazy . My truck cab is mounted with springs on three corners and the gas tank is mounted with springs on one end for the frame flex . Your truck is probably the same . Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted August 23, 2020 Report Share Posted August 23, 2020 stiffen the joint with an inner liner...weld the seams...fish plate the joints... 1 Quote Link to comment Share on other sites More sharing options...
JBNeal Posted August 23, 2020 Report Share Posted August 23, 2020 (edited) C-channel frame rails are typically boxed with similar strength flat steel, not another frame...steel of this vintage is typically 36K, so beefing up a frame with 50K steel would have some unintended consequences, as stresses could now transmit through the new steel to weakened areas in the original frame and exacerbate flaws such as cracking and tearing. So when it comes to working on truck frames, it's not just a question of adding more material but what kind of material, how much material, and where the material is located...even newer trucks, with fully boxed frames, have strategically placed doubler plates to absorb and transmit stresses under certain loading conditions... Edited August 23, 2020 by JBNeal 1 Quote Link to comment Share on other sites More sharing options...
50mech Posted August 24, 2020 Report Share Posted August 24, 2020 (edited) It's not just something thought of, it's done on a daily basis. I'd suggest downloading the chassis PDF here. https://www.gmupfitter.com/pages/best-practice-manuals Extending wheelbase/frame splice procedure would apply to reinforcing or replacing just as well. I'd say your best options would be to either treat the rusted area as a single splice if it's concentrated enough or simply replace the section and treat it as per the chassis best practices. One note..pg6 line 10 on the right side they state figure 7 is acceptable and 8 is preferred. It is actually 8 is acceptable and 7 is preferred....it becomes clear as you read the reasons for the preference. Edited August 24, 2020 by 50mech 1 Quote Link to comment Share on other sites More sharing options...
gramps1951 Posted August 24, 2020 Author Report Share Posted August 24, 2020 2 hours ago, JBNeal said: C-channel frame rails are typically boxed with similar strength flat steel, not another frame...steel of this vintage is typically 36K, so beefing up a frame with 50K steel would have some unintended consequences, as stresses could now transmit through the new steel to weakened areas in the original frame and exacerbate flaws such as cracking and tearing. So when it comes to working on truck frames, it's not just a question of adding more material but what kind of material, how much material, and where the material is located...even newer trucks, with fully boxed frames, have strategically placed doubler plates to absorb and transmit stresses under certain loading conditions... since I was thinking of using an old b3b donor frame it would be same vintage and thickness. But most likely will not be doing that just asked if anyone had seen it done. Quote Link to comment Share on other sites More sharing options...
gramps1951 Posted August 24, 2020 Author Report Share Posted August 24, 2020 1 hour ago, 50mech said: It's not just something thought of, it's done on a daily basis. I'd suggest downloading the chassis PDF here. https://www.gmupfitter.com/pages/best-practice-manuals Extending wheelbase/frame splice procedure would apply to reinforcing or replacing just as well. I'd say your best options would be to either treat the rusted area as a single splice if it's concentrated enough or simply replace the section and treat it as per the chassis best practices. One note..pg6 line 10 on the right side they state figure 7 is acceptable and 8 is preferred. It is actually 8 is acceptable and 7 is preferred....it becomes clear as you read the reasons for the preference. great info like anything there is always more to doing it right than what you first think. 1 Quote Link to comment Share on other sites More sharing options...
Dave72dt Posted August 26, 2020 Report Share Posted August 26, 2020 GM used to do the overlap frame boxing on passenger car frames for a number of years , and for the most part was fairly unattractive, even if functional. No, I haven't seen it done on any of our truck frames personally. My own thoughts are when you stiffen the frame, you have to take a serious look at the suspension. Leaf springs on all four corners doesn't allow for much articulation so the frame has to be able to flex. With a stiffer frame the articulation would need to come from the suspension itself to avoid creating stress points in the frame. My frame is fully boxed and much, much stiffer but the suspension is also much more responsive with an independent front suspension and coils on the rear. Just my theory and shoot it down if you want, but it makes sense to me. Quote Link to comment Share on other sites More sharing options...
Tooljunkie Posted August 27, 2020 Report Share Posted August 27, 2020 15 hours ago, Dave72dt said: GM used to do the overlap frame boxing on passenger car frames for a number of years , and for the most part was fairly unattractive, even if functional. No, I haven't seen it done on any of our truck frames personally. My own thoughts are when you stiffen the frame, you have to take a serious look at the suspension. Leaf springs on all four corners doesn't allow for much articulation so the frame has to be able to flex. With a stiffer frame the articulation would need to come from the suspension itself to avoid creating stress points in the frame. My frame is fully boxed and much, much stiffer but the suspension is also much more responsive with an independent front suspension and coils on the rear. Just my theory and shoot it down if you want, but it makes sense to me. This makes perfect sense. something has to give. my frame was cracked around 3 out of 4 cab mounts. Too much flexing. I fish plated over the cracks with 1/8” mild steel. These old frame rails are quite soft compared to the 1/8” i used to repair it. back in the 50’s the roads left a lot to be desired, as did the tires. most of these trucks will have an easy life compared to when they were new. Quote Link to comment Share on other sites More sharing options...
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