Author Topic: Petrol tanks fixings  (Read 1886 times)

0 Members and 1 Guest are viewing this topic.

Phil C

  • Golden Flash
  • *****
  • Posts: 1913
    • View Profile
Petrol tanks fixings
« on: 30 March, 2018, 13:28:44 »
I've bought, from Draganfly, some centre bolt fixings (chamfered rubber, two spacer tubes, washers, etc) for my 1965 B40F. Rupert Ratio (vol 2, p. 204) tells me:

"...the critical part is the spacer tube inside the rubber, which must be of the correct length to permit the rubber to be compressed by the right amount as the centre nut is tightened.This tube is approximately 1/4" shorter than the top surface of the rubber."

I've just measured my tube and my rubber: the tube is just over 3/8" shorter than the rubber. Is that too big a difference? I guess I could just try it and see, but thought I'd ask your opinion(s), as I reckon some of you will know.

Thanks in advance.

Phil.

AWJDThumper

  • Empire Star
  • *****
  • Posts: 881
  • Dandy Beagle D14 C15 B40 B40WD B44 B25 B50 A10 A65
    • View Profile
Re: Petrol tanks fixings
« Reply #1 on: 30 March, 2018, 14:57:03 »
It will be fine but make sure the washers either side of the rubber are at least the same size as each end of the rubber.

Phil C

  • Golden Flash
  • *****
  • Posts: 1913
    • View Profile
Re: Petrol tanks fixings
« Reply #2 on: 30 March, 2018, 16:10:46 »
Thanks. I've just noticed that when I put the bolt, spacers and rubber together, the bolt doesn't protrude through the top, so it's not possible to get the top washer(s) and nut on without compressing the rubber in some way first, or shortening the long (bottom) spacer. My spacer is 1 and 7/8" long. Is there any disadvantage to shortening it by, say, 1/4" or 3/8" or something like that, to allow me to get the washer(s) and nut on? That would seem the obvious, simplest way. AWJDT, I think you said something a while ago about having to shorten a spacer?

Also, the Draganfly website drawing shows a variety of small washers (plain and spring) under the top nut. The BSA service sheet no.64 (in Rupert Ratio) shows no smaller washer, just the wide washer which sits on top of the rubber, with the nut tightening straight onto it. I'm guessing the service sheet method is fine? Or either way, I guess?

Phil.

Phil C

  • Golden Flash
  • *****
  • Posts: 1913
    • View Profile
Re: Petrol tanks fixings
« Reply #3 on: 30 March, 2018, 16:48:12 »
Further to my previous email, I notice that the new bolt I have is quite a bit shorter than the old one(which is not in the best of nick - threads worn, bolt slightly bent). The old one was 4 and 1/4" long, whereas the new one is about 3 and 3/8". I'm inclined to use the new bolt and just shorten the bottom spacer.  Phil.

Phil C

  • Golden Flash
  • *****
  • Posts: 1913
    • View Profile
Re: Petrol tanks fixings
« Reply #4 on: 30 March, 2018, 17:50:10 »
AWJDT, Just found your old message about your tank fixings sizes.  Phil.

AWJDThumper

  • Empire Star
  • *****
  • Posts: 881
  • Dandy Beagle D14 C15 B40 B40WD B44 B25 B50 A10 A65
    • View Profile
Re: Petrol tanks fixings
« Reply #5 on: 30 March, 2018, 18:29:51 »
Phil. If I was you, I would work out what the minimum length is for the long spacer to project at least 1/2" above the bottom of the central tank tube. This is the minimum height you need to achieve for the bottom of the rubber bung. This measurement will then tell you how much shorter you can make the long spacer and whether the bolt is actually long enough. I'll also have a go and check the bits for my C15 are ok.

AWJDThumper

  • Empire Star
  • *****
  • Posts: 881
  • Dandy Beagle D14 C15 B40 B40WD B44 B25 B50 A10 A65
    • View Profile
Re: Petrol tanks fixings
« Reply #6 on: 30 March, 2018, 18:48:58 »
Just done the measurements.

For my C15, the bottom of the tank tube is 1 1/8" above the top of the bracket for the central bolt. To position the bottom of the rubber bung, 1/2" above the bottom of the tank tube, the bottom spacer needs to be 1 5/8" long - at the moment my long space is 1 7/8" long and needs 1/4" chopped off.

The short spacer is 1" long and my bolt is 3 3/8" long and so 3/4" of the bolt projects above the two spacers leaving just enough rubber to fit the washers and nut before compressing the rubber.


Phil C

  • Golden Flash
  • *****
  • Posts: 1913
    • View Profile
Re: Petrol tanks fixings
« Reply #7 on: 30 March, 2018, 19:23:10 »
I measured: 

Top of bracket to top of hole:  4  7/16".

Length of hole:   3  3/4"

Therefore top of bracket to bottom of hole must be 11/16"

So min tube length = (11/16 + 1/2" =) 1  3/16"

This seems a lot different from yours. Maybe I should check my measurements.

By the way, where do you get the half inch figure from? Is that simply a judgement?

Phil.

AWJDThumper

  • Empire Star
  • *****
  • Posts: 881
  • Dandy Beagle D14 C15 B40 B40WD B44 B25 B50 A10 A65
    • View Profile
Re: Petrol tanks fixings
« Reply #8 on: 30 March, 2018, 21:20:52 »
Phil.  This was measured on a C15 - I'll measure my B40 tomorrow which might be different. The 1/2" is what I would consider to be the minimum height for the bung although you might get away with 1/4". I assume the mountings for your B40 have the correct rubber buffers?

Phil C

  • Golden Flash
  • *****
  • Posts: 1913
    • View Profile
Re: Petrol tanks fixings
« Reply #9 on: 30 March, 2018, 21:36:33 »
I think so, yes.  And I think my measurements, if correct, will mean I can reduce the length of my bottom spacer enough to be able to get the top washer and nut on and still have the half inch minimum you recommend inside the tank tube. I'd be very interested to know the measurements on your B40. Thanks very much again.   Phil.

PS  Obviously in my previous email when I said minimum tube length I was referring to min spacer length.

hoogerbooger

  • Royal Star
  • ***
  • Posts: 245
    • View Profile
Re: Petrol tanks fixings
« Reply #10 on: 30 March, 2018, 23:34:18 »
Should it help I've just taken some measurements for my B40F

bolt is 4 7/8" from top of frame bracket & just protrudes above the tank tube when tank is on.

lower washer is fixed at 2" above the frame bracket

lower side of lower bung  (is cut a little unevenly & may not be the proper bung)  & is positioned 1 1/8" to 1 1/4" above the bottom of the tank tube.

The metal tube /sleeve for the bungs seems to have been shortened & is 1"

top of the this tube sits 7/8" below top of the top bung. ( so well more than 1/4" recommended)

The top of the top bung to the top of the tank tube ( at the back/lowest side) is 1/2"

(I have thin pipe-lagging on the frame below the tank....but as far a I can see it serves no purpose as the tank sits on the rubbers - so won't affect the measurements)




AWJDThumper

  • Empire Star
  • *****
  • Posts: 881
  • Dandy Beagle D14 C15 B40 B40WD B44 B25 B50 A10 A65
    • View Profile
Re: Petrol tanks fixings
« Reply #11 on: 31 March, 2018, 08:47:39 »
Just done the measurements.

For my C15, the bottom of the tank tube is 1 1/8" above the top of the bracket for the central bolt. To position the bottom of the rubber bung, 1/2" above the bottom of the tank tube, the bottom spacer needs to be 1 5/8" long - at the moment my long space is 1 7/8" long and needs 1/4" chopped off.

The short spacer is 1" long and my bolt is 3 3/8" long and so 3/4" of the bolt projects above the two spacers leaving just enough rubber to fit the washers and nut before compressing the rubber.
The corresponding measurements for my B40F are:

Bottom of tank is 3/4" above the bracket for the central bolt. To position the bottom of the rubber bung 1/2" above the bottom of the tank tube, the bottom spacer needs to be 1 1/4" long - this is exactly what mine was.

However, I've just increased the bottom spacer to be 1 1/2" long and that left me with about 3/8" of the bolt sticking up above the rubber bung which was enough to easily put the nut on.

Phil C

  • Golden Flash
  • *****
  • Posts: 1913
    • View Profile
Re: Petrol tanks fixings
« Reply #12 on: 31 March, 2018, 14:28:34 »
Hoogerbooger,  Your set-up appears to be different from mine, eg you clearly have a much longer bolt at 4  7/8" (mine is about 3  3/8") and you have two bungs to my one.  AWJDThumper, Your measurements are 1/16" different from mine, which doesn't seem a lot in this context. As I say, I think I can reduce the length of my bottom spacer enough to allow me to get the top nut on to the bolt whilst the spacer will still protrude at least 1/2" into the bottom of the tank hole.  Thanks very much both of you for taking the trouble to take and post the measurements - interesting and useful.

I'm still a bit uneasy about why there was so much foam rubber under my tank (I've removed it) and what the piece of rubber (I guess something like an inch and a half long, see photo) was for - it fell from somewhere under the tank when I removed the tank. Also why there was string wrapped around the rear rubber button somehow(could the string have been holding the flat rubber to the rubber button in some way? - can't think how or why, unless the rubber button is not thick enough). Anyway, I guess I'll see when I come to refit the tank.  I'm assuming my three rubber buttons are standard.

Thanks again anyway.     Phil.

Phil C

  • Golden Flash
  • *****
  • Posts: 1913
    • View Profile
Re: Petrol tanks fixings
« Reply #13 on: 31 March, 2018, 17:56:35 »
Further to my previous email about fixings, foam rubber etc under my petrol tank, etc, here are some photos of my rubber mountings.  They are about half an inch deep.   They look pretty standard, don't they?  Note however the cushioning taped behind the rear mounting - I wonder why that's there?       Phil.

Phil C

  • Golden Flash
  • *****
  • Posts: 1913
    • View Profile
Re: Petrol tanks fixings
« Reply #14 on: 31 March, 2018, 17:57:50 »
Here they are!