Otter LRC CM4647296 comes home

[Jordan Baker]

Hi David.

Yes it’s one tank construction but divided in the middle. There is also a baffle on each side. Two drains and two fill ports. Two fuel senders as well. Two fuel lines run in the frame rail up to a standard CMP type 3 way fuel selector valve. On the dash there is one fuel gauge with a tank selector switch.

[Grant Bowker]

I think I'd be willing to give it a go for repair.
The obvious caution is to be at least 100% sure any gas fumes are gone before applying heat/flame to restore the solder joint(s) that opened up (or for any other reason). When I was doing my CMP tanks, I put a shop-vac to blow into the tanks for a couple of days out in the sun to warm and ventilate. I used the mark 1 nose as fume detector, do you know anyone who has access to combustible fume detectors? (Occupational safety, fire investigator, police/military bomb section etc.) There don't seem to be sharp creases - good news - gentle persuasion can work instead of needing brute force. If you aren't sure of safe soldering in your shop, you might be able to do the straightening and joint preparation and farm out the soldering to a radiator shop. One of the challenges will be to get to the corners of the tank to apply outward pressure if needed. One end looks as if it is enough de-soldered that it might be worth considering finishing removing the end cap to make it easier to restore the end cap and tank body and then reinstall the refurbished end.

[David Herbert]

Since it has already been in a fire and exploded I doubt that there are any combustable fumes in it ! I think it will straighten out quite well once you remove the damaged end plate which will probably be the hardest part. I assume it is spot welded or crimped on prior to soldering to seal it ?

David

[David Dunlop]

Based solely on your photos, Jordan, that tank looks a lot shorter than a pair of 15-cwt tanks would be, sitting end to end, but it looks a lot chubbier. It must have been fun to fill in the field.


David

[Jordan Baker]

I took another quick look at the tank tonight. Both ends are ruptured so I’ll have to remove the end pieces and figure out how to undo the crimping. I suspect both baffles have popped looking at how the parts of the tank are more “round” than other parts. Removing the end caps will also be good for getting the inside completely clean.

As for lingering fumes. The fire would have burned off anything that was still there.

The double tank is 41” long, 18” high and 12” wide. It works out to about 30 imperial gallons. The filling spot definitely isn’t handy.

[David Dunlop]

I have been thinking about the fuel tank situation with your Otter, Jordan, and wanted to offer some observations and ideas on the topic.

Essentially, you have one large fuel tank, sealed and divided at the centre-line, mirror imaged outwards from that point, and it needs a bit of TLC.

If it were my tank, Jordan, the first thing I would do is study the hell out of it to learn as much as possible before attempting any disassembly. It should be able to tell you a lot about itself. You already know the tank was in a fire with enough volatiles still inside it to cause it to explode. If both tanks were expanding under pressure at the same rate during the fire, then the internal pressures on either side of the centre dividing plate would be equal and that plate would stay in place and should be OK. As pressures built within the tank, the external sheet steel would start to stretch and expand and the end plates begin to stretch and bulge out until one, or both ends ruptured to release the internal pressure. Did both ends eventually rupture, or just one? Also look at the amount of stretching evident on the sheet metal of both sides of the tank. Do they both look equally bulged out, or is one side more pronounced than the other? The side with more stretched sheet metal was likely the tank with the most volatiles in it during the fire. As an aside on this point, and bearing in mind potential years of fiddling may have happened, but did the fuel tank selector valve still point to the tank showing the greatest expansion/rupture? That would show the valve was still it its point of last use when you obtained the Otter, still set as left.

Then take a close look at the centreline of the tank, where the dividing wall is fitted. What you would like to see here, is that the dividing wall survived the stretch and rupture process of the tank in the fire. If you have a large roofing square handy, it will help in the analysis. If the dividing wall held its ground, visually, you should see something of a wasp-waist effect on the sides of the tank at the centreline. The centreline will reflect the factory shape and dimensions of the tank with things getting bigger as you move away, either side. All four sides at the centreline should also be very close to square and flat, versus other cross-sections moving towards the ends of the tank.

At this point, you might want to jury rig a small inspection lamp from an automotive lamp socket and bulb with enough leads you can lower it into one side of the tank through the filler and cover the filler with a rag in a dark room. What you don’t want to see when looking into the other filler tube is any sign of the light being visible from the other tank. You may want to use a flex mirror to have a better look. If all looks dark, the dividing wall is likely in good shape. If you do see some light, see if you can determine if it matches up to the most bulged side of the tank. The dividing wall may just have been pulled away from the one side and it may be an easy fix once you access it.

The baffles should have been immune from any pressure imbalances during the fire and rupture, but it is possible one, or both might have been torn free from a side of the tank that suffered a lot of expansion stretch. I am not sure how the baffle plates are designed or mounted, but if the edges were folded to 90 degrees for spot welding to the sides, it is possible that as the sides expanded, they may have pulled some of these tabs beyond 90 degrees, opening some up enough they might break free.

The stretched sides of the tank can be shrunk back to normal with a little time and patience, a blow torch, or heat gun, cold water and rags, but you will need to have a good look inside the tank to fully assess the amount of work involved. Both end plates will need to be studied to see how they were put together. Not an impossible task overall, but certainly an interesting one.There are likely not many original Otter fuel tanks out there today. Don’t rule out restoring this one until you absolutely have to, Jordan.

Best regards,


David

[maple_leaf_eh]

^^^ I am fundamentally lazy, and always try to be respectful of the craftsmen who designed and built machines long before my birth. They knew what they were doing. So, repairing the tank would be my first encouragement. And how you do it is a matter of applying old-style skills, which seems to be exactly how you are approaching all the steps of this build.

As the others have said already, keep up the good work and thank you for sharing the journey.