No radical changes are highlighted in Bacon's Resto book. Just the usual minor detail changes through the years.
Cosmo
Cosmo
Triumph Unit Frame Differences pre/post 1964.
Does anyone happen to know the differences between the early and late unit construction 350/500 frames? I think they changed in some way for the 1964 models.
I really wanted a David Bird hardtail (4" stretch; 2.5" drop) for my 1962 3TA/5TA frame as I wanted the bottom tubes without the flat area for the battery, but unfortunately their hardtails won't fit the early unit frames for some reason.
Factory Metalworks look as if they sell a bolt-on hardtail for my frame, which they list as fitting all 1958 - 1974 unit frame loops, which is good news, but I'm curious to know what prevents the David Bird hardtail fitting the earlier unit frames when the Factory Metalworks one does fit.
Thanks
I really wanted a David Bird hardtail (4" stretch; 2.5" drop) for my 1962 3TA/5TA frame as I wanted the bottom tubes without the flat area for the battery, but unfortunately their hardtails won't fit the early unit frames for some reason.
Factory Metalworks look as if they sell a bolt-on hardtail for my frame, which they list as fitting all 1958 - 1974 unit frame loops, which is good news, but I'm curious to know what prevents the David Bird hardtail fitting the earlier unit frames when the Factory Metalworks one does fit.
Thanks
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Okay, thanks It's odd about the hardtail situation then.
It's odd about the hardtail situation then.Yes, I sent a message to Todd via their contact details. He replied saying they "will not fit on the early 500 front section". Obviously I don't doubt his word, but I'm curious to find out the differences between the early/late unit construction frames that are causing the problem with my one!
I seem to remember somewhere that 1964 was mentioned in some significant way with regard to hardtail fitting, but I can't find it now.
My frame sounds very similar to yours. Early in the production the petrol tanks were fitted as stressed frame members, bolting to the same lugs that your bolt-on top rail is attached to, but the tanks were prone to splitting, so Triumph changed the mounting to underneath the tanks via brackets/rubber mounts and fitted the bolt-on top brace between the old tank mounts, like with your frame.
I've been thinking about this and I wonder if they won't sell the hardtails for the early frames in case someone is still using the original stressed member petrol tank, which I presume would receive considerably more stress via the hardtail compared with the factory swinging arm set-up. If they used to split with a swinging arm rear suspension then a hardtail would surely make things worse! I suppose I could ask them directly, but this makes a good subject for the forum in case anyone else is researching it, so I've brought the subject here.
I seem to remember somewhere that 1964 was mentioned in some significant way with regard to hardtail fitting, but I can't find it now.
My frame sounds very similar to yours. Early in the production the petrol tanks were fitted as stressed frame members, bolting to the same lugs that your bolt-on top rail is attached to, but the tanks were prone to splitting, so Triumph changed the mounting to underneath the tanks via brackets/rubber mounts and fitted the bolt-on top brace between the old tank mounts, like with your frame.
I've been thinking about this and I wonder if they won't sell the hardtails for the early frames in case someone is still using the original stressed member petrol tank, which I presume would receive considerably more stress via the hardtail compared with the factory swinging arm set-up. If they used to split with a swinging arm rear suspension then a hardtail would surely make things worse! I suppose I could ask them directly, but this makes a good subject for the forum in case anyone else is researching it, so I've brought the subject here.
Thanks for that. Very interesting to hear!
My reasoning with the stressed member-plus-hardtail versus factory swinging arm subframe is that the forces fed to the subframe attachment point (near the tank's rear mounting point) would be greater due to there being no change for energy to be dissipated (hardtail) compared with the swinging arm's suspension set-up.
If their hardtails do actually fit then I'd like to get one of theirs because I want the option of avoiding the flat section in the bottom tubes for a battery tray. I don't intend to use the stressed member tank as I want to make my own, and use a purpose-built bolt-on top tube of a different shape from standard.
My reasoning with the stressed member-plus-hardtail versus factory swinging arm subframe is that the forces fed to the subframe attachment point (near the tank's rear mounting point) would be greater due to there being no change for energy to be dissipated (hardtail) compared with the swinging arm's suspension set-up.
If their hardtails do actually fit then I'd like to get one of theirs because I want the option of avoiding the flat section in the bottom tubes for a battery tray. I don't intend to use the stressed member tank as I want to make my own, and use a purpose-built bolt-on top tube of a different shape from standard.
That was the only thing I could think of. If yours fits then mine should too, so I think I'll go with that and see what happens. Worst case scenario is that I need to modify it or find a front frame loop that does fit.
Thanks again; I'll post some photographs once I get started!
Thanks again; I'll post some photographs once I get started!
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