Hirtenberger .61 with a sliding piston carburetor
 

I have been given this engine. It has a very unique carburetor in that it uses a sliding piston to control the air fuel mixture. I am interested to know if anyone has used this engine, how it performs and how fussy it is. The carburetor alone is quite unique and it would be fun to fly! Any information is appreciated. Hopefully the photos were loaded. Thanks for your input

RE: Hirtenberger .61 with a sliding piston carburetor
 

The HP is a fantastic engine...one of the early models was perhaps the first adopter of the schneurle porting system. You have the "Gold Cup" version...lots of power and outstanding Austrian engineering. I've had several over the years and loved them. Randy at MECOA.com still sells them and has parts. You've got a keeper.

RE: Hirtenberger .61 with a sliding piston carburetor
 

The HP Gold Cup 61 was a good light weight 10cc engine. She responds to a pipe better than most sport engines. The carb is very nice with a very crisp transition. Although the bell crank linkage can wear a little faster than one might want. She also likes lower nitro than some popular Asian brand. IIRC, I used 5% nitro with 100% castor oil with 18% total oil. But FAI 80/20 fuel would also work.

All the best,

konrad

RE: Hirtenberger .61 with a sliding piston carburetor
 

I've one like that and it works beautifully. Lots of power from the engine and easy to adjust. I also tried a more conventinal one, but I couldn't appreciate any differences. This one is so cool!
Beppe

RE: Hirtenberger .61 with a sliding piston carburetor
 

Unique, Ilike unique.

RE: Hirtenberger .61 with a sliding piston carburetor
 

Gentlemen, thank you for your comments. I appreciate your experience with this engine. So far I havelearned that it likes low nitro, high castor fuel, it is powerful and runs well. GREAT NEWS!!!. Is an OS #8 glow plug sufficient? It has a plug with an idle bar currently, but I have never been a fan of them. Thanks again for the information.... Great photos Beppe!

RE: Hirtenberger .61 with a sliding piston carburetor
 

You should not use an idle bar glow plug in a schnuerle ported engine, well only as a last ditch effort. Glow plug recommendations are a lot like carb setting. There is no one glow plug/setting that works for all. You need to set the engine up and test with a tach. But as a general rule if you are going to use low nitro fuel start with a hot glow plug.

I know just about nothing of the OS brand of glow plug. I had a full set of Rossi glow plugs that I used to set up my engines. Once I found the one that ran best I then looked for a cheeper version in an other brand.

RE: Hirtenberger .61 with a sliding piston carburetor
 

Properly designed it should not need an idle bar plug. I am not a huge fan of OS plugs, I prefer Merlin full reach plugs and he has a huge number of heat ranges to choose from. Probably would start with a Merlin 2003HD.

RE: Hirtenberger .61 with a sliding piston carburetor
 

Last time I looked the OS plug was nether a long or short reach plug. That was one of many reasons I stayed away from them. Your HP uses a long reach glow plug.

RE: Hirtenberger .61 with a sliding piston carburetor
 

I use Enya 4 on my HP engines.
Once I tried a Fox miracle plug and that worked good to.

RE: Hirtenberger .61 with a sliding piston carburetor
 

The O.S. #8 glow plug will work nicely in your engine. We used O.S. #8 plugs in HP engines when we were the service center for HP in North America a number of years ago.

RE: Hirtenberger .61 with a sliding piston carburetor
 

Bax,
Am I in error about the length of the OS glow plug?

Now I'm not questioning your operational success with the OS plug, but did it fit the combustion chamber? I often ask why wear a size 10 shoe when you have a size 11 foot?

Engine designers spend a lot of energy trying to make the transition from the glow element to the combustion chamber as smooth as possible. You will have noticed that in the sub 2.5cc class of engine they often use a glow head insert. Or for bigger engine you will see the Nelson type glow plug/head with its chamfered seal area used instead of the 1/4x32 glow plug.

Also what was the fuel that you used (as the agent for HP) were the OS #8 worked so well for you?

All the best,

Konrad

RE: Hirtenberger .61 with a sliding piston carburetor
 

The original poster asked if the OS #8 plug was sufficient and Bax answered that it is.

RE: Hirtenberger .61 with a sliding piston carburetor
 

Actually the sliding piston carb is not unique to HP - OPS and Picco are other examples of this style of metering.

RE: Hirtenberger .61 with a sliding piston carburetor
 

Thanks for the info. This was the first time I have seen this type of carb, so it would be better to say that it was unique to me. I am not familiar with the engines you mentioned either (and probably quite a few others). I wonder why the piston/sleeve metering is not more common?

RE: Hirtenberger .61 with a sliding piston carburetor
 

A few of the recent model car Nitro engines have slide valves

RE: Hirtenberger .61 with a sliding piston carburetor
 

You're quite right, it is not common among the engine brands most airplane folks deal with, no nitpicking intended. OPS and Picco are Italian engine makers, in fact the "P" in OPS is for the same Picco, but these are different companies. Rossi is another but AFAIK they use rotating barrels, I don't own any. Personally I am a bit of an OPS fan so have 5-6 engine with this style of carb. OPS was a very popular brand in AMA pattern in the heyday of the pattern 10cc engines, the gold head "Super 60" is a classic and still a performer by anyone's standards. They are still popular in marine, the .67 and .80 are killer engines. Picco is a significant player in the car engine market and that's one place you'll often see slide valve carbs. For aircraft they require a bellcrank mechanism to give the side to side linear motion while keeping a low frontal profile.

I have no idea if there are functional advantages to one or the other, could be as simple as two different design philosophies.

RE: Hirtenberger .61 with a sliding piston carburetor
 

I also asked with what fuel, this is very important when selecting a glow plug. Not sure the OP knew to ask.

The slide valve carb shown is a great design as it does NOT result in a plenum around the spray bar as the throttle in closes. I seem to recall it also has an accelerator pump function (I may be in error about that).
http://www.rcuniverse.com/forum/fb.asp?m=10057899

Edited
To add the word NOT

RE: Hirtenberger .61 with a sliding piston carburetor
 

I am quite lucky in that the original manual came with the engine. The manufacturer indicates that the piston carb "injects" additional fuel into the intake manifold when it is rapidly opened. Naturally I will try to verify this when I have time to attempt starting and tuning the engine. As far as the glow plug is concerned, a "long reach" plug is recommended. In addition a colder plug is recommended for higher nitro content while a hotter plug is recommended with lower nitro. Comparing the OS "F" plug to a "#8" plug, it appears the filament should extend further into the combustion chamber with the "F" plug. The "F" plug should be a pretty hot plug since it is recommended for four stroke engines. I have never ordered a Merlin plug and it is difficult to see from the web site, which might be a long reach plug and which are not.

RE: Hirtenberger .61 with a sliding piston carburetor
 

Glow plugs aside, You'll love the carb!

You might want to keep an eye on this thread.
http://www.rcuniverse.com/forum/m_10015277/tm.htm
That HP carb might come up for discussion. Since I have one I can say it will at some time.

RE: Hirtenberger .61 with a sliding piston carburetor
 

Merlins are all long reach unless specified, such as 1/2A plug, Nelson, etc.

RE: Hirtenberger .61 with a sliding piston carburetor
 

While I like and use some of the Merlin plugs, I have to agree, their website is about as clear as mud in some cases.

Why can't they just say "long reach" or "short reach" or provide more pictures?

RE: Hirtenberger .61 with a sliding piston carburetor
 

Wait till you have a few of the Merlin plugs rolling around in the field box, then try to sort out their model and heat range without any markings.... [:'(]

RE: Hirtenberger .61 with a sliding piston carburetor
 

Ihave taken to marking them with a scribe but most people open the package and install the plug then dont remove it until it burns out anyway.
And the color on the plug indicates its heat range. Red Green and Blue, hot ,med and cold.
We have discussed the web page and Iwish Icould take charge of it and make it more clear but he is having it professionally run and it costs money to make changes. Ihave a few too many projects now with my own web page to administer.

RE: Hirtenberger .61 with a sliding piston carburetor
 

Quote:

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ORIGINAL: ABORH

...Is an OS #8 glow plug sufficient? It has a plug with an idle-bar currently, but I have never been a fan of them.

---

Aborh,


The OS #8 has a correct heat range for this engine - a bit on the high side, though.
The OS #10 (formerly the A5) is what OS subscribes for engines over .60 in displacement.

But this plug and all other normal OS glow-plugs, are of medium length.
If this plug is fully tightened into the head of your HP engine, it will remain slightly recessed; i.e. sunk into the head and shy of the combustion chamber surface.

This is even the case in all OS mid-large engines and I have no clue why OS chose to do so.


Any other full-length (i.e. 'Long') mid to cold glow plug will do the job right.
Rossi R4, or R5 are good, as is the Novarossi C-6S. The Fox standard and 'Pro' long, the Traxxas Super Duty long and many others, don't cost nearly as much as the OS and do have the right length.


Your engine is schnürle ported and needs no idle-bar to run well.