Otter LRC CM4647296 comes home

[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.

[Jordan Baker]

Great observations David.

The tank was held down by three substantial metal straps so that kept most of the tank in shape and forced the weaker end plates to pop. Both ends are popped. I can tell the interior baffles have come loose on one of their four sides. This goes for both baffles.

Plan is to remove the end plate and then further inspect and see what’s going on. Right now I’m working on removing the senders. Got some screws backed out. Working on the others.

I firmly believe this tank is repairable. The steel is in great shape with next to no rust. Most of the tank still has its exterior KG#3 paint.

Ultimately the tank will not be visible except for a small part at the top where the fill ports are. The rest is all behind and inside a plate steel box.

[Jordan Baker]

Removed the ends of the fuel tank. At first I tried melting the solder out and uncrimping the edge. It wasn’t working too well and was making a mess of the edge. I ended up using the flap disk in the grinder and simply took the top of the fold off. This went very quick and I was able to remove the end panels. They will get formed back into shape. As suspected the internal baffles were popped from a few tank walls. I will remove them as well. This will give me the access I need to get the rest of the tank cleaned up. This will also let me work on getting the side walls of the tank back into shape. I also removed the senders and the pickup tubes.

[Jordan Baker]

Lastly I found some kind of screened filter loose inside the one tank. Not sure if it’s original but more research is required.

[David Dunlop]

Not exactly a ‘Holy Grail’ but quite a surprise inside the tank.

It looks far too course to be a fuel filter in the conventional sense, but it looks like it might slip into the throat of the filler pipes to catch larger objects. If filling these tanks was an awkward task in a confined space, the filler caps might have had chains fitted to prevent their loss into an inaccessible place. One would also not want to lose one of those chains into a fuel tank, so those screens might have been used to prevent important stuff from falling into the tanks for all eternity.

Another long shot.

Back in the 70’s, I worked up in Yukon doing geology, using helicopters in remote areas. We had a string of 45 gallon drum fuel cashes strung up the Richardson Mountains to give the pilots the range and endurance they needed to move us about. Part of the kit they carried for refuelling was a chamois and a large hand fuel pump for the drums. They would wet the chamois and give it a good ring out and line their fuel funnel with it before pumping the fuel in. For some reason, the chamois let the fuel through but stopped any water from getting into the helicopter fuel tanks. It also stopped sediment passing through.

Maybe that screen served a similar purpose when used with a petrol can and flex hose fitting...?


David