mtntopgeo

My Feedback: (12)

Got hold of a NIB HB .15 this morning. Before running it, I tore it down to check the innards. No swarf, dirt, or even a sign of dust or other foreign matter. Also beautiful machine work. (things are looking up.) Then, the big end of the con-rod caught my eye. It is unbushed. I have been using 15% Omega, with 4 OZs, per gallon, of castor added, (Comes out 'bout 19% oil, with castor making up 'bout 41% of the total oil content.) on my old baffled, cast iron piston Enyas. Planned on using the same fuel on the HB, but that unbushed rod has me concerned. Re-assembled the engine, & mounted it on the test stand. No instruction sheet, so took a guess at the prop size (7x4.5). Compression was "sky high" so I started with 5% nitro. That rod had me concened, so I went with 25% castor. I found a few threads where advice was given to use castor because of the cast Iron piston, but no-one even mentioned the unbushed rod. Maybe I'm overly concerned. Anyone have any experince with fueling this engine? Anyhow, I fired the thing up (third flip), got the needle close, let it run a few min., then twicked the needle a tad, & made a WOT rpm check. Got 16,200, so I feel that the prop is definetely in the ball park. Home for this engine is gonna be an original Lil' Extra. (The last two Counterfit Lil'Extras that I bought were very tail heavy with a lite engine mounted. The HB is only 5 & 1/8 OZs, so should do well in the "better balanced" original unit. Besides the fuel thing, I'd also like to know where (RPM) these things like to be run. I'm feelin pretty comfortable at the 16K area, but that may change when I get some response from you guys. ............. George K.

ffkiwi

I think you're on the right track-but check the MECOA website-they now own HB (as well as HP.....which causes a bit of confusion from time to time)-there is probably an HB instruction sheet somewhere there on the website-failing that you can ask the question on their forum and Mr RJL will probably answer your query directly. The original HBs were German made (HB= Helmut Bernhardt) till MECOA took over the brand about a decade or so ago. IIRC they did a .12, a .15, a .20 and perhaps some larger sizes..............I don't think the brand made a lot of market penetration in the US or anywhere else other than its native Germany.

ChrisM
'ffkiwi'

Mr Cox

Both the HB .12 and .15 are nice engines and very light for their size, 5.6 oz with the muffler, not bad for a ballbearing (single) engine . The .15 beats the Norvel .15 in terms of weight (but not power), and if you use the included radial mount option you'll save even more. I only run full castor 20-25% in lapped engines, and have not seen any problems with the unbushed conrod. Unbushed rods were a very common thing (still is) and it is not a problem on castor fuel for sure. You might want to check the surface finish of the crank pin, it should be near mirror finish even before it is run-in, or it will quickly grind away on the conrod (I've had that problem on another engine brand).

HB made a whole series of engines (up to .61) but I have only used the smaller ones. The .021 and and up also came in hotter versions with PDP porting (I have one NIB) but not the .12-.15 so they are a bit timid by todays standard. At their time they were the very highly regarded with the fashionable Perry carb and the little muffler. There are also extensions available for the muffler.

The manual doesn't state any prop sizes, but I have tried 7x4 -8x4 props and I think 7x5-8x4 is about right. You have to remember that these are old designs which gave their max power at much lower revs compared to the more modern ABC engines. The manual state a maximum power of 0.375hp at 13000rpm and recommended revs up to 16000rpm. Your 7x4.5 should be fine but you might want to try an 8x4 too, depending on the plane.

Meccoa still has some parts for the .15 (I bought a spare piston/liner set not long ago) but they're out of piston/liners for the .12.

combatpigg

My Feedback: (3)

I run my 200 mph Nelson .40 on 25% straight castor oil, even though the experts say you can run on 20%.....
If you ever run into a scenario where running too much oil in an airplane engine did harm, please make me one of the first persons on your emergency list to notify.

I don't care what brand your engine is, if it wont run good on 25% castor, then it doesn't deserve to be mounted in an airplane.

mtntopgeo

My Feedback: (12)

OK guys, thanks for the input. The mecoa site list the engine as out of production, but they do have spare BUSHED connecting rods in stock. (at least they say that they are.!!) For now, I'll just use the stock rod with the 5% nitro, 25% castor. Made another run on the engine. Same fuel, but with an 8x4 MAS S2 prop. Got 15,200 RPMs. Not bad for an old cross scavaged relic with a cast iron, baffled piston. Looks like either prop will do well. Generally with this size, 15 powered sport plane, I favor the 8x4 prop for all 'round performance. Plane is gonna come in 'bout 26 OZs (I was hoping for < 25). This engine is a tad heavier that that of MR. COX. Have only seen one of these before, & think that the radial mount was removable (screwed into the crankcase???) On this unit, the radial mount is part of the crankcase casting. Also, the muffler seems to be more "stout" than the one I've seen before. Still, the weight (with muffler, + extension) only comes out to 6.0 OZs. Now for the 6 & 1/2 month wait for flying weather. Time to start on another project. ...................... George K.

Mr Cox

The .12 and .15 are identical apart from the liner and both have a cast in radial mount at the back. The stock muffler is very lightweight, about 1/2 oz if I remember correctly. 15200rpm is a very good number, I think mine only did about 14000-14500rpm (that was on a Graupner 8x4 though). I haven't checked, and can't remember, if mine are bushed or not on the conrod, it shouldn't be an issue as I see it (you still need the castor oil for the piston/liner). I've had mine in a stick-type plane (Topstick ARF), here is a shot of the stock muffler with the muffler extension mounted:

Walther

My Feedback: (1)

If it is still needed, I think I have the manual for this engine. These are some really good engines.

Mr Cox

I have manuals for .12, .15 and .21 PDP engines, they are more less the same. Once you know how to run lapped engines it is pretty much the same. Kind of an Ikea instruction sheet that one doesn't need to read...

The manual does not give any recommended propsizes.

Mr Cox

I checked the manual a bit more in detail, it is the regular stuff with safety warnings etc.
Recommended fuel; anything with 20% of oil (this was before the synthetic oils I guess)
Run-in time: 1-2 hours
Glow plug: HB or KB long reach, with or without idle bar (the one without idle bar is hotter)

So common sense works just as well. Use 25% pure castor for running in and one can drop to 20% once run in. The piston and liner looks like steel piston in steel bore to me. So short runs, and heat cycling (finishing lean) is the way to go. Nitro around 5% will do, no need for excessive nitro levels here.

mtntopgeo

My Feedback: (12)

Mr. Cox, Thanks for digging up the extra info. ................. George K.