Freeparaglider

Hi Tyor,

Can you tell me what kind of dimensions your fuelcan is for the Storch. I have bought it second hand, with an electric motor on it, but will put my NGH38 on it. The fueltanks I have do have problems with the cockpit underside......
can you make a foto for me from your inside of the Storch.

Many thanks from Belgium

Peter

SrTelemaster150

Now there's an ideal airframe for a gas 4-stroke.

james88

The new 38cc A38 OHC

SrTelemaster150

I fail to see see the advantage of overhead cams in an engine that will only turn 7000 RPM.

Freeparaglider

Hi Sr T,
I'm not sure what you mean.....
I just want to see with the 112' Black Horse Fiesler Storch users, which fuel tank dimensions they are using in there Storch.....because I have trouble to fit mine....with the removable cockpit....

Peter

SrTelemaster150

.

I'm saying that with the limited power output of a 4-stroke gas engine, the Storch is an ideal airframe. As far as your gas tank mounting issues, the fuel economy of a gas 4-stroke will require a very small fuel load for a reasonable flight time. That & the fact that location will be less of an issue than with a glow engine due to the gas engine's pumper carburetor makes the options for fitting a suitable fuel tank very broad.

I would venture to say that an 8oz tank would have plenty of capacity for a reasonable flight time.

Freeparaglider

Ha, thx for the reply...will keep in the mind...have some small ones here. Now busy with the balance of the storch, damn that tail is quit heavy, how many weight did you guys put in front, using the NGH38. The manual states that 140mm of G is mandatory and even 150mm is ok, for slow landings, etc.....but still I have the idea, to need quit a bit of weight extra ( even with ignition battery and servo power in front ( NiMh 5 cells- 4500mah) x 2 ( ignition and one for the servos, just for the weight).......would prefer using LiFe...

grts

peter

SkyPilot101

Allways nice to see a new engine! BUT that A38, with it's open valve train, with no oiling to the cam looks like a Bad Idea ! http://www.google.com/url?url=http:/...cH892CSt5YEGsw

SrTelemaster150

I wonder what happens when the belt fails.

ALFIEV

All goes quiet........ except for the RC pilot who is heard repeatedly yelling F$$k F$$k F$$k!!

SrTelemaster150

I would expect a little bit of noise until the valves auto clearance themselves with the pistons. Then it goes quiet.

earlwb

Well it is likely a toothed belt, so its highest stress would be at idle. So the teeth on the belt would strip off at idle. I used to have a Chevy Chevette that like clockwork every 12,000 miles it would stop running in rush hour with me at the front of the line waiting for the stop light to turn. Sure enough the teeth on the drive belt for the cam would strip off at idle.

the pope

Anyone heard from Turk 1 lately ? He used to be on these forums regularly with his words of wisdom . Cheers the pope

Mikola

this is the fail 70cc version with cam cover and metal chain LOL http://shop.pichler.de/Gas-Engine-Air-Power-A70S

SrTelemaster150

You were lucky it wasn't an " interference" engine. Many OHC engines eat the valves/piston when the belt fails.

earlwb

Yeah I remember quite a few people with Ford Escorts having the cam drive belt fail at highway speeds with the obvious consequences of the pistons and valves making contact. For whatever reasons the Chevy Chevette's cam belt would fail at idle though, which was nice in the sense that it didn't damage the engine from the failure. But it always liked to do it when you had the car in the worst place ever to have it quit.

Now then I ran and flew a Webra T4-80 four stroke engine for a long time in a P-51 Mustang and the engine never had problem with the drive belt. I regret selling the engine and airplane, but that is life.

So I don't see it being a problem with the drive belt on the OHC gas four stroke engine. But like someone mentioned, there is little to no reason to have overhead cams on a engine that runs in the 7 to 8 thousand RPM range. But the OHC engine would be interesting though. I think that maybe going with a desmodromic OHC valve setup (like Ducati uses) would be better as one could reduce the valve spring tension a lot and maybe improve valve life and reduce wear on the valve seats, etc. But then if the engine is only running in the 7 to 8 thousand RPM range would it even be worth it.

SkyPilot101

The limiting factor probably is due to valve float. These overhead cam engines have a major flaw in that there is no direct lubrication to the cam/valve area in either of them. Well, just add a drop of oil to the moving parts before each flight, how long you think that's going to last on the hot head of a petrol burner!

Mikola

drop of oil before each flight ? wouldn't it be better to add automobile grease on the cam area ?
anyway this engine will have to be installed in inverted position

PARDAL

Why not use Molykote spray??

SrTelemaster150

It has more to do W/valve train geometry than engine speed. Even @ idle some of the valves will remain open. If the geometry is such that the open valves will interfere W/ the piston, then it is an "interference" engine & damage will occur.

I had an '85 VW Golf 1.8L strip a belt while accelerating. It did no harm to the engine.

mpascual

My Feedback: (1)

I'm testing the new OHC A38 engine and i'm very impressed con how ir performs.

Is not a hi-rpm engine, better with a hi-load prop.
With a 20x8 wood prop, it's about 6.100 rpm.
No belt-drive problems yet

Soon i will show the results

PARDAL

Finally the parts for my ngh 38 arrived and now it is runing ok.
I made some mods, first the conrod bearings, both had clearece of 0,05 mm that I judge too much. I milled broze plain ones with clearece of 0,015 to 0,02 mm, I trough in the litter the oil ring and stended oil connection to the nopple in the camshaft position.
Now it is running happily in the nose of a Miles Sparowhawk 62cc.
Th oil now is 20;1 as in my Saito 57t in the nose of a J-3 1/3 scale. Saito uses plain bearings bare aluminun.
By the way, with crank balanced it is not vibrating. The pics show running full bore.

earlwb

I am surprised they didn't have needle bearings on the connecting rod. Although a bushed rod is fine, it is just that I thought it had needle bearings on the rod.

mogman

It does have needle brgs. on the rod.

captinjohn

The photo shows a bushed rod!!!