Fuel cap lost

[Nev]

Rob we now have them working so they can be dropped into the filler neck very easily, and removed easily with one hand. I'll post a short video once we're confident they're working consistently. Using a tool to tighten and loosen certainly ensures they're tight enough. Having a pin to stop the lower from rotating inside the neck makes a huge difference.

[Nev]

Here's a short video showing where we're at with the fuel caps.

This isn't a mechanical lock, and it does benefit from using a tool to help tighten and loosen the cap. However, they are now very easy to install and remove, and appear to be quite secure in position.

We also think that when mechanically locking caps are available they should prove extremely popular.

We had hoped to avoid specialist machining, but after trying so many ideas and combinations, the solution we've got at this stage used a lathe to reduce the shank size from 34.35mm to 33.35mm, size -323 O rings, and the installation of a pin to prevent the lower body from turning. The pin made a significant difference, and would be a great addition even if you didn't change anything else. When loosened, the fuel cap inserts easily inside the filler neck with no resistance, and is lifted out with no resistance. We expect that after sitting in place for a week or two, there may be some slight friction to remove the cap, but it should be minimal.

Obviously time in use will be needed to highlight any issues. I'm very interested to see if there's any changes with the larger vent hole and the increase in tank pressure. I plan to test them inflight later this week.

Update: These caps worked well over many hours. The one downside was they required a tool of sorts to tighten and loosen them. I used a U shaped piece of plastic. However they were very secure, and very easy to install and remove. Once another set of fuel caps arrived, we modified them in a similar fashion but only turned the shank down to 34mm. These ones are easily installed and removed by hand (with no tool). See Bissetg's post below. Grant found he had a slightly different fit on each side, and didn't need to reduce the cap shank size at all. Simply by replacing the O rings with a smaller size (-323) he got a good fit. Others have reported this worked for them too, Due to the variation in filler neck Inside Diameter, and the variation in fuel cap shank Outside Diameter, you may or may not need to reduce the shank diameter.

[Linusbear]

Kevin kindly used my BH as a test bed for his personally designed fuel caps for the last several years, including several mods which improved an already functional design.

I cannot describe the pleasure of refueling now as opposed to four letter word blood pressure raising experiences with the original. I did lose two of the old ones.

Kevin has a box of the fuel cap parts but no time to organize assembly or order parts from machine shops. Full attention goes to his aircraft completion.

It will be worth the wait and he should be flying in time for Bob's BBQ.

Scott Williamson
924PL

[Nev]

Yep looking forward to seeing a couple of Kevin's fuel caps!

[Bissetg]

Nev kindly sourced some O rings of the smaller size. My ID on the filler necks is 44mm, the fuel cap inserts are 34.2 mm, by going to the smaller size O ring I can now very comfortably insert and remove the caps by hand. However I could only get one cap to lock as the base kept turning with the vent spigot, the other cap worked flawlessly. As a result at Nev’s suggestion we have put pins in the caps connecting the base to the top to ensure that turning the vent spigot at the top compresses the O rings.

The result is two fuel caps that are firm but not difficult to use, and lock effectively with a tightening of about 210 degrees consistently. The caps now work far better than I thought they would.

[kestrel]

Today is Thanksgiving in the U.S. and I am thankful to Nev and any others who have contributed to this investigation into improved fuel caps. Today was the first use of my recently modified caps and the experience was so much more pleasant! I installed O-rings that were one size smaller in diameter and engagement pins on all 4 of my caps. What an amazing improvement!!

[svyolo]

I did the fuel cap mod to my caps yesterday. I used the Dewalt "portable shop lathe" method. 1/2-13 bolt thru the cap, chucked into a 18v drill, held by my vise. 100-150-220-400 wet/dry sandpaper. My caps measured 1.35" before the mod and were nearly impossible to insert. Both are about 1.30 and still snug, but slide in. The roll pin was easy with the same drill. I thru drilled the. Thru drill the bottom, and drilled 1/4" into the top. Drill out the bottom about 8-10 numbered bits bigger. Very easy to do.

Great idea, whosever it was.

[Nev]

Dewalt portable shop lathe - Ingenuity at its best !

[Gerhard Rieger]

Covers still to be made to fit flush around the caps, keep it simple

[African Bear]

I've had trouble with galling in the threads to the point of seizure and having to machine out the male thread. I remade the inner from brass to get away from the same metal galling and have found that they are much easier to tighten and , touch wood, have been very secure.

[jaredyates]

It is very important to lubricate the coarse threads with fuel lune to prevent galling. I had one get stuck also.