HB .40 PDP Engine - RC Groups
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Nov 01, 2012, 12:41 PM
What, Me Worry?
edbu1's Avatar

HB .40 PDP Engine

I recently acquired an HB .40 PDP 2 stroke engine at an estate sale. The sellers didn't know the history of it since it belonged to grandpa who has passed. The engine did not come with a box, but appears to me to be un-run and un-mounted. Don't see any marks on it at all, and the finish looks great. Piston looks very clean looking through the exhaust.

What I want to know is, were/are these strong running engines? If it was/is a strong runner, I may decide to sell it. If they were average, then it's probably not worth much and I may as well keep it and use it. So, is this a strong engine or a so-so engine? What does the PDP stand for?
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Nov 01, 2012, 01:52 PM
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surfer_kris's Avatar
The HB engines are very nice engines, and in particular the PDP ones. The engines are oldschool cross-scavenged, while PDP stand for Perry Directional Porting (extra ports on the side of the piston baffle) and that gives the engine an extra umpf over the non PDP engines. In fact these can compete with the more modern schneurle ported engines.

You'll need a full castor fuel and only 0-5% nitro, a long run-in and they'll last for a long time.
Nov 01, 2012, 03:48 PM
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earlwb's Avatar
Yeah they are quite strong runners compared to the regular baffled piston engines of that time. They are sort of in between a baffled piston engine and a Schnuerle ported engine in power. The larger crankcase with a larger crankshaft and intake valve porting meant that the engine could breathe better and run higher RPMs too. We ran a couple of those many years ago in our local Quickie 500 races. Back then the rules were the engine had to have a baffle on the piston and not exceed the .40 engine size displacement. The HB PDP engines left the K&B .40 engine powered planes in their wake and just ran off and left them all behind. The racing committes then prompty amended the rules banning PDP porting too.
But it was fun while it lasted.
Nov 01, 2012, 08:11 PM
I am 5' 8" the Taube is 7' 4"
Clancy Arnold's Avatar
I had two HB .40 engines in a Control line scale model years ago. The model was a C-7A Caribou with 76 inch WS and 14 lbs. I entered it three times in FAI F4B at the US NATS. In 1985 it took 4th place,1986 it took 3rd place in 1988 it took 2nd place. I was a judge in 1987.

The HB .40's I had turned 10 x 6 wood props at 14,000 RPM on 10 % fuel. When flying the Caribou I leaned back about 20 degrees and adjusted the throttles to just keep me from falling over back-wards.
Nov 01, 2012, 09:26 PM
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downunder's Avatar
If yours is the black head "Blitz" then I have a scan of a review done by Peter Chinn here.
Nov 01, 2012, 11:55 PM
the great Gassif´er
Originally Posted by surfer_kris
You'll need a full castor fuel and only 0-5% nitro, a long run-in and they'll last for a long time.
Max 5 Nitro is correct, but the PDP has no special oil requirements.
If your locally availlable synthetic oil does not give problems in other engines, it will not in the HB too.
If your locally availlable Synthetic is no good, then yes, I would say use castor.
But the HB's never needed castor to survive like the lapped piston/steel liner engines.

It has just an anluminium piston with (if I remember correctly) Dykes piston ring, and that tends to gum up and stick more if full castor is used.

Run in time is AFAIK just the normal 2 hours: 1 hour on the teststand, one hour in the air.

I really liked those engines, had several of them way back. They all managed to survive my lack of knowledge of those days long enought for me to think of them as good engines

Brgds, Bert
Nov 02, 2012, 12:44 AM
jeffie8696's Avatar
IN an older engine like that I would use a generous amount of lube, about 20% lube minimum would be my personal choice just out of paranoia maybe.
Nov 02, 2012, 01:58 AM
the great Gassif´er
Yeah, probably.... Note, I didn's say anything about the amount of oil, just that it doesn't need castor to survive, depending of course on the quality of the oil you are using if it is something different than castor.

It is not paranoia I think, older engines did not have the material quality and surface finish modern engines (can) have.

Brgds, Bert
Nov 02, 2012, 12:16 PM
jeffie8696's Avatar
It confuses me when people choose the fuel with the "minimum" suggested oil percentage. Why would I want "minimum" protection and lubrication in my engine?
As an example Cool Power is advertised as having 17% lube, however many engine manufacturers state 18% "minimum" fuel required.
Nov 02, 2012, 12:33 PM
Registered User
I checked, MECOA (www.mecoa.com) does indeed have a sheet on the HB. They recommend 20% total lube for breakin, then any commercially available fuel thereafter. No 100% Castor recommendation either, blended fuel is just fine. The key is the 20% lube. They also say it takes about an hour on the test and a hour in flight before it is broken in.

Anyway you can read up on it and get prices from the web page. HB were good engines, still are, just dated.
Last edited by Chip01; Nov 02, 2012 at 12:35 PM. Reason: Spelling
Nov 02, 2012, 12:40 PM
the great Gassif´er
Because manufacturers hate claims.... that's literally all there is to it.

For example OS knows perfectly well, that their engines can survive on less oil.
They design engines, they are not stupid.... they KNOW, that a 15 cc fourstroke needs less oil than a 1.5 cc 2stroke....
They KNOW, that there are synthetics that perform better than castor (not all, and this is not meant to start the discussion about that) but still they only HAVE to warranty your engine if it is run on fuel containing at least 18% Castor, regardless of engine type or size.

They do give good service, and they still will repair most things under warranty, but it just gives them a legal possibility to refuse warranty.

It is not an uncommon practice for manufacturers of whatever item, to put one or two conditions for warranty in their statements, that are very hard to comply to or very likely to be ignored, so if they want to, they have a legal ground for not honouring a claim.

People don't want "minimum" protection.... the just figure that the fuel blender probably has tested the stuff otherwise he would not dare sell his blend.

Brgds, Bert
Nov 02, 2012, 01:22 PM
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surfer_kris's Avatar
These engines are from the 70-ties and they need the fuel of that time. Castor was the lubricant and nitro was expensive in europe (it's a German engine). For the non-ringed engines 20-25% all castor is the way to go, with 0-5% nitro. I can check the manual too when I'm back home.

Sure you can try with a mix of synthetic and castor oils etc., but you cannot use a fully synthetic oil in the non-ringed engines, that I'm sure of.
Nov 02, 2012, 03:41 PM
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surfer_kris's Avatar
Just checked the manual, it is very unspecific and only states 20% oil.
Nov 02, 2012, 04:04 PM
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kimchiyuk's Avatar
I have this engine in a hobbico superstar with 88 flights. Before that I had the engine on an airboat with around 30 hours use. And...I got this engine used. It still has the same compression as the day I got it. Im not big on worrying about the fuel I use as I personally would rather spend time on other aspects of the hobby, but I use S&W 10% which is a blend and is what I've always used in it.
Nov 02, 2012, 10:46 PM
jeffie8696's Avatar
Methanol is cheap.

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