Dempster bonnet

[CTXmiller]

While skimming the FB Marketplace, I saw this Dempster which had a unique bonnet with a filler spot and/or dipstick. Hadn’t seen this before.

[Wayne]

Pretty neat. Southern Engineering at it's best. Never need to remove the bonnet and loose your seal.

[FlJet]

Well crap. When you install a bonnet what do you use to seal it? Wasn't on my radar until I read this.

[Wayne]

Some had gaskets I think. We need Windy Bob he could answer all these questions in an intelligent manner. No guessing!

[CTXmiller]

Some had gaskets like the Baker Monitor (WB, etc.) and some had lip joints (maybe not the correct terminology there). Keeping rain and dust/debris down from accessing the internals of the gearbox was desired. Using non-detergent oil allows the dust/debris to sink to the bottom of the gearbox as opposed to suspending the grudge and clogging any oil passages necessary for oiling bearings.

[FlJet]

"Lip Joint" sounds like my situation. My bonnet sits onto of the case, the case and bonnet overlaps, the bonnet on the outside, the case on the inside. I'll get humidity condensing in my case but there's nothing I'll be able to do about that even if I sealed the bonnet to the case.

[Terry]

On the last Dempster I worked on the gasket was gone. So I went to the hardware store and bought the cotton clothes line rope. The kind grandma used for her clothes line and glued it in the lip with gasket sealer.
Right or wrong that is what I done. Seams to work.
Terry

[Ron Stauffer]

Burdick & Burdick out of El Paso did helmets like that on the bigger E & F Aermotors. I dont think they ever were a Dempster so maybe they were copied. There was no dipstick just a filler tube and a cap.

B & B helmet.jpg

Ron Stauffer
Montrose CO

[windybob]

That is not original to Dempster. lol Looks to be a radiator cap. If it has a pressure reading on it, don't exceed that oil pressure in the head. Oh make sure you glue, gasket, weld, or anything else to keep the helmet on airtight. lol then you can fill the oil up to the neck on the filler tube, and try to keep dumping it in while it's all leaking down the pumprod and out the snout. lol

I use rope for a gasket in the helmet. A little glue holds it in. 3-M super weatherstrip adhesive.