A post-event education on exhaust flap valves
One thing I have become exceptionally good at, is doing my homework after I start something.
In the old image below, circled in red is the top of the RFM exhaust, which features a flap valve and arm / hinge mechanism in the centre. I had gotten pretty far down the rabbit hole of scratching a replacement when I decided to find something out about it. And I did find two important things out.
Thing #1: Tigers didn’t always have these flap (or non-return) valves, they were standard issue only until around September of 1943… so I could in hindsight have omitted them… which would have been much easier, and preferable! The RFM kit doesn’t give you the option of omitting it, but perhaps they could?
Thing #2: The flap valves in normal operation were locked open with a pin, so they are always canted up, as shown in this sketch found on David Brydens Tiger 1 website (link to actual page, where I learnt all of this is here - Mufflers | TIGER1.INFO). The RFM kit part is shown closed, which would be uncommon. (The purpose of the valve is that when closed, it enables the Tiger to deep water wade).
Now, I really wish I knew these two things before I am where I am now, because i’ve ended up where I have to fit a flap valve, and I have to fit it closed, due to me not drilling a hole for the exhaust but instead gluing a solid round block in the exhaust centre as can be seen in my previous post.
I wish I wasn’t here, because my scratched flap valve is a bit ugly, and a bit oversized:
But now I know for next time at least!