Author Topic: Re: Douglas Mk 5 Fuel tank  (Read 947 times)

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Offline HughesNigel924

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Re: Douglas Mk 5 Fuel tank
« on: 14 Sep 2021 at 15:07 »
Hi,
My name is Nigel and have just had my fuel tank repaired,restored and re painted.
Just now ready to put my bike together again.
However when putting the tank back I am having a problem slotting this in place.
The two brackets with the three location holes on it has seemed to of moved inwards by about 1 mm!
What is the
 best and safest  way to protect my freshly painted petrol tank in order to open the bracket (s).
Please help!
Trying to ride to the Hinckley motor show on this Sunday 19th.
 
( Normally the only Douglas on show!!)
Thank you in advance
Ps Any Douglas owners going on Sunday from Leicestershire/Warwickshire?

Offline eddie

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Re: Douglas Mk 5 Fuel tank
« Reply #1 on: 14 Sep 2021 at 18:16 »
Nigel,
         Before trying to put the tank on the bike, try offering up the strap under the front of the tank - if the restorer did a pressure test after repairing your tank, he probably put a band around the tank to prevent it from trying to open out. Subsequent releasing of the pressure may have resulted in the tank then pinching in. If this is the case, try wedging the tunnel open again until the strap will fit - but be careful - the new paint will probably cope with the flexing, but that may not be the case with any filler that may have been used.
   Do not attempt to run, or ride, the bike without the strap in place - it is there to prevent cracks generating from around the top, front of the tunnel.

  Regards,
                Eddie.

Offline Vitesse

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Re: Douglas Mk 5 Fuel tank
« Reply #2 on: 14 Sep 2021 at 19:06 »

Trying to ride to the Hinckley motor show on this Sunday 19th.
 
( Normally the only Douglas on show!!)
Thank you in advance
Ps Any Douglas owners going on Sunday from Leicestershire/Warwickshire?

Well I would (Mk4, live just S of Hinckley) - except my tank is still in Norfolk for repair! I might get over to collect it this week but I doubt it.

Offline Pallijen15

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Re: Douglas Mk 5 Fuel tank
« Reply #3 on: 15 Sep 2021 at 14:07 »
Hi Nigel, when I bought my MkV the front part at the start of the tunnel had been brazed due to a hairline crack. This must have been due to having no strap in place because when I took the tank off there was an obvious home made strap fitted. It's important to have the correct thickness rubber buffers for the rear tank to frame mounts also. If the tank is in contact with the frame it will crack there as well. Paul J

Offline HughesNigel924

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Re: Douglas Mk 5 Fuel tank
« Reply #4 on: 16 Sep 2021 at 10:38 »
Hi Eddie
Thank you very much for your reply.
When you are explaining about the strap I have a black bracket to attach the fuel tank on.
I am wondering now if the strap is missing?
Also when offering up the tank to the head stem the problem is the location bracket is too narrow to slot on.
I am still unsure how to open this up as this only needs to opened up by about a mm.
Sorry if I am not understanding your resolve as I feel to me this is delicate process as not for me to damage the tank. Thank you again.
Nigel.

Offline HughesNigel924

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Re: Douglas Mk 5 Fuel tank
« Reply #5 on: 16 Sep 2021 at 10:48 »
Hi Vitesse,
I hope you get your tank back in time from Norfolk.
With my Mk 5 I am not confident of solving the problem of fitting my fuel tank due to it being a little narrow to slot straight on. I have asked Eddie again to help so l can get the right advice.
I was also going to ask if you would like to meet up as we are both live locally? ( Covid dependent of course)
I live very near to the Triumph factory who offer fantastic coffee.
Nigel.

Offline HughesNigel924

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Re: Douglas Mk 5 Fuel tank
« Reply #6 on: 16 Sep 2021 at 11:08 »
Hi Paul J
Thank you for your reply.
I only have a black bracket to hold the fuel tank . I am not sure what the strap is I need to investigate

Regards
Nigel.

Offline eddie

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Re: Douglas Mk 5 Fuel tank
« Reply #7 on: 16 Sep 2021 at 11:22 »
Nigel,
          In your original posting, you stated that the tank had been away for repairs, etc. I assumed this involved welding or brazing (and therefore some distortion). Subsequent pressure testing may also have affected the shape of the tank. Now, on Mark series machines, the rear tank mount is a shallow channel section on 2 legs. The front strap is an identical, but loose channel section that bolts to the 2 bosses under the front of the tank - this prevents the front of the tank from flexing (and cracking around the front of the tunnel). The pitch of the 2 bosses should be 4" - if it is less than that, the sides of the tank have been pulled in by the welded repairs - this will also affect the space between the 2 front mounting brackets (as you are experiencing). If the bosses are less than 4" pitch, you may be able to use 2 pieces of timber and a spacing block to wedge the tunnel open again until you restore the 4" pitch. With that done, check whether the front mounting plates will go over the front head lug on the frame - if it does, all well and good! - if not, then it might be better to ease a little off the width of the head lug - a local repair to the frame paintwork will be a lot less expensive than a tank paint job!

  Hope this helps,
                          Regards,
                                       Eddie.

Offline Vitesse

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Re: Douglas Mk 5 Fuel tank
« Reply #8 on: 17 Sep 2021 at 21:18 »
Hello Nigel,
Sadly I'm not getting my tank back - tank lining bloke is away till Oct!  Meeting up sounds good and after Oct I'll have a tank for you to compare to!!  As you can see I'm just down the road from you.
If you are at Hinckley I'll look out for you - I'll be on foot for a walk around rather than displaying anything.
Stephen

Offline HughesNigel924

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Re: Douglas Mk 5 Fuel tank
« Reply #9 on: 19 Sep 2021 at 07:52 »
Hi Eddie,
Thank again fo you advice.
My tank was sent to Kevin Newton@ Devon tank restorers and was really pleased ( be it expensive)with the work that was completed.As I wanted to make sure this was not a quick lining job the tank was opened up from the bottom.A process was used (as per their website) and then welded up.
So I will try your suggestions,
Thanks
Nigel.

Offline Pallijen15

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Re: Douglas Mk 5 Fuel tank
« Reply #10 on: 20 Sep 2021 at 17:19 »
Hi Nigel, since you have your tank off I wonder if you could do me a favour. I have just bought the front tank strap from the club spares to replace the home made one I have been using but it doesn't fit. I need to elongate the holes about 5mm each side. The tunnel on my tank measures 6cm width at the front and 7cm at the rear. Just wondering if yours differs from front to back. Thanks, Paul Jensen. P.S. My tank has had a (failed)brazing job done on it by a previous owner.

Offline eddie

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Re: Douglas Mk 5 Fuel tank
« Reply #11 on: 20 Sep 2021 at 18:01 »
The tunnel should be parallel at about 66mm wide.

   Regards,
                 Eddie.

Offline Pallijen15

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Re: Douglas Mk 5 Fuel tank
« Reply #12 on: 22 Sep 2021 at 14:31 »
Thanks Eddie, I am going to use an air bag which I can pump up by hand, see if it will push apart slightly. Before I bought the bike a previous owner  must have left the strap off. That must have been when it cracked and was brazed unsuccessfully, then a home made strap used
 

Offline eddie

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Re: Douglas Mk 5 Fuel tank
« Reply #13 on: 22 Sep 2021 at 14:52 »
Paul,
        Using an air bag may be the gentlest way of prising the tunnel open, but it is likely to deform the sides of the tunnel before actually spreading it. I would suggest it might be better to use a couple of pieces of timber (say 2 pieces of floor board about 600mm long) placed end on into the tunnel, then drop another block of timber in between them as you prise them apart, and lever the tunnel open. That will apply the load to the more rigid fold between the tunnel and the base of the tank. The timber can also be left in place while the original repair is rectified - the timber is expendable, rather than risk damaging the air bag.

   Regards,
                 Eddie.

Offline douglas1947

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Re: Douglas Mk 5 Fuel tank
« Reply #14 on: 25 Sep 2021 at 17:18 »
Hi,

the way Eddie tells works well.
I had the same problem after  I had tested a welded tank with air presure (very small preure!).
I wondered the tunnel was then too narrow.
To get it wide enough again, the timber blocks and timber wedges (and perhaps a lever for tyres) will give back the old shape.

Michael