# "Dorothy" - Choppergirl's $38 Volmer Jensen VJ-24W antique ultralight motor glider ### Help Support HomeBuiltAirplanes.com: Status Not open for further replies. #### TFF ##### Well-Known Member Re: "Dorothy" - Choppergirl's$38 Volmer Jensen VJ-24W antique ultralight motor glide

It might take a couple of trips to prove you say who you are, when cold calling; so what, that's what puts value in it.

#### Pops

Log Member
Re: "Dorothy" - Choppergirl's $38 Volmer Jensen VJ-24W antique ultralight motor glide My grandson started out going with my neighbor all summer for 3 years selling tickets and refueling the Stearman used in giving rides at airshows starting at 15 years old. Then got a job at an FBO refueling airplanes. Has 7 type ratings and now flys a Cessna Citation X. Flew for the airlines for about 3 years and didn't like it, happy now. Where there is a will, there is a way. It will be hard work, but you can do it. Dan #### BBerson ##### Well-Known Member HBA Supporter Re: "Dorothy" - Choppergirl's$38 Volmer Jensen VJ-24W antique ultralight motor glide

I use Ospho (from hardware store) for removing light rust on steel.
Just spray with squirt bottle or dip some on scotcbrite pad and scrub, let set 5 minutes and scrub again, then rinse with water. It converts rust to iron phoshate, ready to paint when dry.
Cleans aluminum corrosion also.
Stings some, mostly phosphoric acid.

#### Angusnofangus

Re: "Dorothy" - Choppergirl's $38 Volmer Jensen VJ-24W antique ultralight motor glide My wife used to know an employment councillor, and he told her that if you want a job at a certain place, you might have to go there at least three times. Usually by the third time they will give in and give you a job. If you get a job at an FBO or somewhere similar, you might be able to work overtime and then take that out in flying. That's how I learned to fly. In the end, I was making parts runs in a 150 when we needed something from a nearby field. Free flying, the best kind. #### choppergirl ##### Banned Re: "Dorothy" - Choppergirl's$38 Volmer Jensen VJ-24W antique ultralight motor glide

A picture down the spark plug hole of my front cylinder, and the Autolite sparkplugs that made me suspicious....

Did I just figure out the cause of a GA pilot crash?

For all the Cuyuna/2si engines the recommended plugs are NKG B8SE. http://zdenterprises.net/2055054.html "...and standard B8ES spark plug used in virtually all Cuyuna & 2si engines."

These spark plugs on my engine are Autolite 4054, which according to the Autolite catalog are equivalent to NKG B7ES:

Autolite - Part Details

If that's the case, they would of run hotter than B8ES which is recommended for normal operation. However I found this in a motorcycle forum:

Forum - Forum - KZrider.com

Skip down to post by "Patton":

"Would mostly rely on using factory recommended sparkplug (B8ES) for most of us under normal riding conditions using the full rpm range in a mix of city and highway riding.

Hotter sparkplug (B7ES) runs hotter to help keep plug cleaner and avoid carbon loading under conditions of sustained lower rpm usage such as plonking around town all the time without some regular higher rpm usage (such as an occasional hard acceleration rip through the gears to "blow it out.") The original Z1 Owners Manual said B7ES could be used during the break-in period if B8ES plugs were fouling, but cautioned in bold print to use B8ES after break-in because continued use of B7ES for hard acceleration or high speed could cause engine damage from overheating. The FSM warns further about preignition and burning holes in pistons."

Well that's exactly what I have here, a hole in the piston.

From: https://en.wikipedia.org/wiki/Engine_knocking

Causes of pre-ignition: "An engine that is running hotter than normal due to a cooling system problem (low coolant level, slipping fan clutch, inoperative electric cooling fan or other cooling system problem)"

and

"While it is not uncommon for an automobile engine to continue on for thousands of kilometers with mild detonation, pre-ignition can destroy an engine in just a few strokes of the piston."

A hot sparkplug that is abnormally hot, from running at high rpm, can cause the fuel to ignite before its suppose to when the spark occurs, correct? I'm thinking like so hot the tip of the plug is borderline glow plug perhaps.

Now I'm conjecturing (having never actually flown one), an ultralight engine is probably going to be run at a very high rpm (90%-100%) during take off climb out and a fairly high rpm (1/2 to 3/4 or 50%-75%) for sustained flight, converting high hp into torque. So normally they run at pretty high rpm where you get the most power out of a two stroke on the power curve.... maybe 75% for fast cruise, 50% for slow cruise.

According to Page 1 of the ULII-02 manual during the break in period the engine shouldn't be run more than 1/2 throttle, then more than 3/4 throttle for the first 12 hours or so, varying the speed under that up and down to wear in the new rings on the honing. A hotter plug would of kept them from fouling at these low speeds, and made sense to be used during this low rpm up and down revving fiddle farting, but past the break in period should of been swapped out for the colder normal B8SE equivalent.

Break in procedure for Cuyuna, Cuyuna UL 430, Cuyuna UL 215, Cuyuna UL11-02

Engine hour meter shows 118 hours. Could it be he forgot to swap in the standard plugs and swap out the hotter plugs after the first 12 hour break in period, and for the first 100 hours got lucky as he babied the plane watching his CHT, not exceeding some temps, until the GA pilot took it up... and not mind the CHT as closely, or even knowing the high end to avoid having not been told that because he wasn't suppose to take it up... blew a hole in the piston cause it was still running those hotter break in plugs... and he aborted a landing and then gunned it to 100% at the end of the runway to clear an upcoming fence...

Did I just figure out why a GA pilot may have crashed the ultralight my engine came off of into fence... sudden loss of power (like 50%!)... from detonation in one cylinder blowing a hole in piston... thusly unable to clear fence after an aborted landing, totaling the ultralight, when he suddenly ramped up power again on an already hot engine to climb and make another go around?

And also thusly figured out, what killed my engine, a spark plug one notch too hot for normal application?

They just assumed it was the GA pilots fault, being he was a GA pilot flying an ultralight and wasn't suppose to take it off in the first place? And they just started salvaging what they could, never once trying to crank up the engine in their garage, being disgusted with the whole affair, after they cut it off the plane from the gas tank and other wires necessary to crank it up. And everyone *assumed* it still ran just fine, cause it was the "GA pilots fault" for running into a fence, not the engines. When maybe it was the owner having the wrong spark plugs in... to begin with... and it was the engine dying at a very in opportune moment that led to the crash?

All speculation, but... this hole in my piston is telling me... then why am *I* here? Holes don't magically appear in pistons.... and the owner and then his friend, the seller, never once trying to start the engine again, just stuffing it in their garage and assuming it still ran, as it was running when the plane crashed (sort of, on one piston!)... before they cut it all out of the wreckage... never to fire it up again.

~

If an HBA consensus agrees my speculation, than TFF, you can now indeed bless me as legit ;-)

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#### blane.c

HBA Supporter
Re: "Dorothy" - Choppergirl's $38 Volmer Jensen VJ-24W antique ultralight motor glide Well say your prayers for the ignorant * that afforded you the opportunity to learn so much about your engine. I hear that snake venom is a growing enterprise. Are you into wandering around (with a trusted friend) gathering snakes and selling them in the venom trade? You seem quick and smart enough not to get yourself bit. Do some research it may be better than the dollar store. #### Dana ##### Super Moderator Staff member Re: "Dorothy" - Choppergirl's$38 Volmer Jensen VJ-24W antique ultralight motor glide

CG,

Could be. But 100 hours is a long time for spark plugs on a Cuyuna. I usually replaced mine around 25 hours; spark plugs are cheap. The engine also may have been running hot due to lean running. Could have been an air leak (crankshaft seals are a likely culprit), or improper jetting. The latter is probably why the Cuyunas got a bad rap; you must pay attention to EGT and jetting. Pilots coming from the GA world where you can just firewall it and forget it had problems. By the time Rotax came on the scene, people had learned how to handle 2-strokes, and though the Rotax engines weren't necessarily any better, everybody had better results with them than the "bad old" Cuyunas.

When I got mine, the engine had been freshly rebuilt by a snowmobile shop after the crankshaft center seal had let go. The engine quit, on the pilot's first solo in a fixed wing aircraft (he was an experienced gyrocopter pilot). He did a great job of getting it down almost on the runway, with nothing but a bent gear leg to show for it. After the rebuild, he put maybe another 5 hours or so on it before selling it to me, and I had some 250 mostly trouble free hours flying it before I sold it to buy my Fisher.

Hopefully your cylinders are OK. New pistons, rings, seals, maybe bearings if it's been sitting long, and you hopefully will be good to go. Oh yeah, and new plugs.

Dana

#### Little Scrapper

HBA Supporter
Log Member
Re: "Dorothy" - Choppergirl's $38 Volmer Jensen VJ-24W antique ultralight motor glide This is a small problem compared to the next 1,000 problems you'll encounter while working on this project. Try to make it fun, that's what it's all about. #### wakataka ##### Well-Known Member Re: "Dorothy" - Choppergirl's$38 Volmer Jensen VJ-24W antique ultralight motor glide

I put a hole in the piston of my Rotax 377 due to stale gas. I had left the cap off the gas tank it had set that way in the hangar for about 3 weeks. With the tank open, the gas had a lot more opportunity to evaporate than with the normal small vent hole. This didn't dawn on me until later. I topped the tank off with about a gallon of fresh gas. The plane made it to about 400 feet on climbout before the piston melted. Fortunately it was high enough to turn back and land on the runway. My partner was flying and wasn't watching the temp gauges, but it's possible there wouldn't have been much indication. If the octane in the fuel is too low, detonation can occur at normal CHT and EGT temperatures.

Gas is cheap compared to pistons.

#### choppergirl

Re: "Dorothy" - Choppergirl's $38 Volmer Jensen VJ-24W antique ultralight motor glide This flying business is complicated and fraught with danger, and seems to require a heck of a lot of inside knowledge and tweaking. I wonder if it's even worth all the hours of work, money, and hair pulling I have to look forward to, only to build something big that becomes a PITA to store and take care of, and then I stumble across a video like this... [video]https://m.youtube.com/watch?v=MKmmQSm7DX8&amp;feature=youtu.be[/video] I hoped my guess was right as the fix of the source of the original failure would then be easy to fix... different spark plugs. I guess I'll rebuild it following along the manual and videos and go easy with it on the ground past it being broken in until I get a notion of how the engine runs and what it likes and don't like and I know every bloody thing not to do with it... put several dozen hours on it just creating windstorms in my back yard. #### bmcj ##### Well-Known Member HBA Supporter Re: "Dorothy" - Choppergirl's$38 Volmer Jensen VJ-24W antique ultralight motor glide

CG, you continue to impress and amaze me! :gig:

#### Victor Bravo

Re: "Dorothy" - Choppergirl's $38 Volmer Jensen VJ-24W antique ultralight motor glide Uh Oh... I'm supposed to be the official smart-a** around here #### blane.c ##### Well-Known Member HBA Supporter Re: "Dorothy" - Choppergirl's$38 Volmer Jensen VJ-24W antique ultralight motor glide

I wonder if it's even worth all the hours of work, money, and hair pulling I have to look forward to, only to build something big that becomes a PITA to store and take care of,.
To late and no hope, you were a born addicted to flying. You poor soul you.

#### TFF

Re: "Dorothy" - Choppergirl's $38 Volmer Jensen VJ-24W antique ultralight motor glide Free plans! We want free plans! #### bmcj ##### Well-Known Member HBA Supporter Re: "Dorothy" - Choppergirl's$38 Volmer Jensen VJ-24W antique ultralight motor glide

CG, you should research for Dan Johnson and Budd Davisson. Maybe your dream job is doing what they have done, writing reviews of different planes. I suppose you could do that without first having your license (flying as a passenger), but could really grow into the field once you have your license and a decent level of proficiency under your belt.

Budd Davisson = http://www.airbum.com/
Dan Johnson = http://www.bydanjohnson.com/

#### Derswede

Re: "Dorothy" - Choppergirl's $38 Volmer Jensen VJ-24W antique ultralight motor glide Uh Oh... I'm supposed to be the official smart-a** around here Son, you got competition!!! And just wait till she mounts twin paintball guns on it for strafing runs!! #### Derswede ##### Well-Known Member Re: "Dorothy" - Choppergirl's$38 Volmer Jensen VJ-24W antique ultralight motor glide

Hmmmm....just did the math on the paintball gun...300 fps is around 200 mph, add 50-60 for aircraft velocity.....now how do you aim? Kentucky Windage or a HUD in your helmet? Next thing we will see will be replica WW1 birds doing dogfights. Winner has the fewest hits. CG, there is a new video game idea for you!