Thorp Air Command - T18.net

Hey all,
I have piston pins and buttons in the works and should have them the next 2 weeks. I have rings in hand. The rings are moly and as such will work in steel or plated cylinders. The pistons will get ordered as soon as I get 2 orders of the same item. 8.25:1 or 10:1, standard or plus .020. Email me to place you order. darmah@ftc-i.net

$1295/set of 4 cylinders.

Thanks,
Dana LaBounty

Hey all,
I had pins made from H13 tool steel that are far superior to anything Lycoming ever made for the O-290. Pistons are being made from 2816 forged slugs and machined to be as light as a cast 6.5:1 piston. Rings are a straight cut moly face top ring. If some one wants a bad ass O-290, get your cylinders plated to standard and have them STRAIGHT bored. You will have a non oil consuming and combustion efficient engine just like all the other modern engines. Talk is cheap, it cost money for this level of quality. 150hp O-290. I have close to $6000 of my own money into these piston sets so far. If anyone has interest let me know.

Dana, I sent you a PM.

Thanks, Keith Schneider

The manufacturer contacted me today with an update. These piston sets are less than 2 weeks out so if anyone wants a set let me know. Keith has spoken for a set and I'm keeping one set for my engine. That only leaves one set.

Dana LaBounty

Dana,

Are the OEM wrist pin plugs also steel? I thought mine were made of aluminum. Changing to steel will add to the reciprocating weight. Also if there are less that 7 HRC points difference the H13 plugs could gall against the cylinder walls.

Just wondering,

Jim

The OEM plugs were aluminum for steel cylinders then bronze for plated cylinders. As the aluminum plugs were used up Lycoming parts manual goes to the bronze for either steel or plated cylinders. I have a stash of new old stock plugs. When exhausted I can have them made for $15/cylinder. Reciprocating weight? You have a 3lb piston, pin and plugs spinning at the awesome speed of 2800rpm. What's a few ounces one way or the other? I had the wrist pins made from H13 so I would have less weight and the strength of the heavy wall pin. The pistons also have been through a internal lightening process. Want to buy a set?

Regards,
Dana

Dana,

No, I have an IO-320 in my plane. I only responded because I thought it was interesting. Did you make the wrist pins dimensionally the same as the OEM ones? I ask because if the wall thickness is less they might be as strong with respect to tensile strength but the stress /strain curve for most tool steel sis virtually the same. This means the pins, although having higher strength properties will deflect more under the same loads.

Regards,

Jim

Jim,

The pins were made with the same internal diameter as the stock pins. Engineering showed these pins to be more than enough for the application and clearly as strong as the Lycoming thick wall pin. The original Lycoming pins usually withstood compression increases well. It's when the engine started getting run at 3000rpm that they had failures. Back in the '60's when gpu's were being converted some were set up with 10:1 compression or more to go racing with the standard pins of late 1930's technology/metallurgy.
I've been told that I have strong survival instincts(chicken shit). These are what I'm building my engine with and will operate such within the prescribed range of the O-290D2.

Dana

I 'won' a new O-290G crankcase on 'epay' last week. I called DIVCO about boring it to accept O-320 cylinders, they charge $200 for that service. However, the person to whom I was speaking said some O-290g cases are too thin and prone to cracking when bored for O-320 cylinders. Modern O-290 pistons save the day!
I asked if there was a way to adapt the single sleeve bearing to the nose of the case in lieu of the two standard main bearings; he said 'no'. I didn't want a constant speed prop anyway...but a little more stability in this area wouldn't hurt.
I have another O-290g case, which has been bored (poorly) for conical mounts. I check it periodically when I think of O-290 upgrades and mods. It was taken from a T-18 that had sat un-flown too long and the steel parts had some rust.
One of the advantages of the O-290G, O-235 and early O-290 mechanical tappet engine case is a set of catch basins along the tappet guides that collect oil thrown off the crankshaft. This oil drains through drilled passages into the pushrod tubes, and over the top of the head where it carries away heat and lubricates the valve stems.
I wonder if adding these catch basins and drillings would improve an O-320 or O-360 case. Just a life extending mod for the engine. Kinda like Ney Nozzles for cam life, or piston cooling jets, or oil cooling tubes to the exhaust valve guides like used on Helicopter engines.
http://occonline.occ.cccd.edu/online/rf ... appets.PDF
This link describes the problems Lycoming has experienced with hydraulic tappets over the years, and some efforts to correct them. It's a little antagonistic, but a good read.

_________________
Scott Emery
EAA Chapter 326
T-18 N18TE

Proper operation of the engine and regular oil changes will most likely give the best longevity with less machine work.
I getting excited as the first batch of pistons should be done next week hopefully.

Everyones best friend, the UPS driver delivered the first batch of pistons today. They are pretty things. I do have all parts on hand now ready to ship. There are a couple guys I have to place calls to as they have said they want a set and I don't wish to disappoint them. If for any reason they don't want them I need $1350 for a full set. Pins/rings/buttons and shipping included. That for all 4 cylinders!