fuel sender

[brettster]

I don't understand what you mean???

[Ragtop]

v8s4me said:

Did you manage to figure out whether the MGB unit was originally designed for horizontal or vertical fitting?

Judging by Google images, it's side-fitting (not sure if you would call that horizontal or vertical?), for example:




That tank is very shallow in comparison with the TVR's - makes me wonder if it will have sufficient range of movement?

Graham

[v8s4me]

Side fitting = horizontal in my book. I see what you mean by the depth of the tank; my guess is that in the ‘S’ tank it will read ‘full’ until it is about half full and then read from there down to ‘empty’. The LR one I used won’t be completely accurate either but it does have a longer swing so it will register a drop in level sooner than I’m guessing the MGB one will. I don’t think it’s too important though, it’s the last couple of gallons you really want to know about so if it’s reasonably accurate from ½ down it’ll be a lot better than a clapped out original.

[phillpot]

brettster said:

It is the MGB one that phillpot recommended suggested

While I will happily take all the credit if it does work ok I really only posted the MGB one as an example of the fitting and terminals!

The arm may well need extending to suit the deeper TVR tank, possibly it will work fine at lower levels of fuel but read full at 3/4ish ?

(the Triumph one I linked to had a longer arm)

[v8s4me]

Take the credit and run

[greymrj]

Yes, there is a major difference in tank cross section isn't there. The S tank is high and narrow and would need a bigger arc. I wonder therefore if the altered original shown was altered because the owner worked out the arc of movement of the sender, compared this to the depth of the tank and used geometry to work out the ideal arm length. My tank is due out soon (major restoration!), I am going to look at those dimensions. It probably means that a lot of senders which use that hole fitting (and there are lots) could be adapted if we knew those dimensions.
Incidentally, stupid of me really, on the very tatty old one I took out some time ago I am pretty sure there was a small fin on the rod. I think I may have a pic somewhere as I tend to take far too many of them!That would presumably have acted as a damper to the effects of fuel surge. I am sure there wasn't one on the new one.

[Ragtop]

greymrj said:

I am pretty sure there was a small fin on the rod. That would presumably have acted as a damper to the effects of fuel surge.

It would need a pretty large 'small fin' to damp the buoyancy of one of these?

[v8s4me]

greymrj said:

....... I wonder therefore if the altered original shown was altered because the owner worked out the arc of movement of the sender, compared this to the depth of the tank and used geometry to work out the ideal arm length. .......

I think there might be a bit of over-thinking here. TVR would have sourced a readily available sender unit and just bent the wire to get an approximate reading. Even on my modern car the fuel gauge isn’t exact across every increment of its range relative to what’s in the tank. It takes over 100 miles before the needle starts to move from full and then it goes from ¼ full to empty in just 50 miles or so. The sender unit is just a little rheostat varying the current to the gauge depending on where the float is. Before I fitted my new unit I measured the resistance across the full range of the swing and found that ¾ ½ & ¼ of the swing didn’t necessarily give corresponding readings for the resistance.

Extending the wire on the MGB one should be easy enough using a bit of brass tube from a model shop. Or just try the Herald one as Phillpot recommends, sorry I meant, mentions in passing

[brettster]

I think phillpot is right again, it will stay full until down about 3/4, but as I need it to tell me when it is empty it doesn't really matter.

[greymrj]

You are probably right Joe, it is the engineer in me trying too hard to do it right and forgetting, as you rightly suggest, that I ought to remember we are talking about TVR here, not BMW!

[v8s4me]

My “modern” car is a Toyota so if that’s vague, expecting much more than a wild guess at an approximation from an off the shelf part fitted to a TVR is asking a bit much.