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NGH 38cc Petrol Four Stroke - now at JE


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Posted by Bob Cotsford on 08/08/2015 17:01:09:

Well, I am impressed. Last night I checked the valve clearances for the first time blushand they were around 10 thou out, so I closed them down to spec 'that's about right'. Today I maidened the Acrowot XL and the NGH ran an absolute treat, no deadsticks, quiet, smooth (for a big single) and started easily on a starter. Did I mention economical? 10 minute plus flights were using well under half of the Acrowot supplied tank.

It's still slightly lumpy at 1/4 throttle, but it's still running in and rich. What have I done to it - 1/8 turn in on the low speed needle, retard the ignition as far as the slots allow and set the valve clearances.

Oh yes, the cheapo noise meter that normally shows 1dBa high compared to our club one was showing under 82dBa at a regulation 7 good paces. That's using the Just Engines exhaust and an APC 18*8. It's not particularly powerful for nearly 40cc, but for the money? Brilliantlaugh

Hi Bob

Thanks for posting your info on the engine particularly the exhaust, could you tell me what the parts you ordered were? I can't fing it on the JE website unless I am missing the obvious!

I could of course give them a ring but I am in a secure environment working at the moment so it is not that easy.

Cheers

Nige.

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Nigel, it's not listed on the JE website, I had to rang them up and ask if they could supply the exhaust separate from the engine. The silencer is just an ASP FS 180 unit with a 90 degree male to female adaptor, but the cylinder head fitting is unique to the NGH and not listed as an accessory.

Sorry

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  • 1 year later...

Ian, I've got them in both the Acrowot XL and WotsWot XL. I can't comment on their longevity as I didn't get a lot of opportunities to run them last year. Probably no more than an hour on the WW one and a couple of hours on the AW one. They start easily enough and run ok with no obvious signs of premature wear though I'm sure they will benefit from more running and a little fine tuning of the carbs. They are no powerhouses but they fly these models ok on 18*10 Hobbyking Aerostar wooden props.

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Bob, Ian, they do get better the more they are run had mine in a Great Planes Curtiss p6e for a while now turning a 20x6 Windsor prop it's a little flexible but it pulls the model around very nicely, it's not an engine I would recommend for the 3D guys but for sport or scale models I think it is perfect, so much so I am thinking of putting it's smaller partner the 30 in a Duncan Hutson Se5a, it's not built yet so that may change but I think it would be a very good match.

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How much use has your NGH 38 had Tony? I am interested as on another thread (?) it was reported that the cam suffered from 'excessive ware' after a short period of running (1h). That may have been a 'Friday afternoon' engine and hopefully a one off, or perhaps the tappets were not set correctly causing some damage? I bought one of these engines from HK when they were 'on special', as I planned to put it in my World Models PA25 Piper Pawnee. Does anyone think it will be man enough for the job? I am not planning on any 3D flying with it!

Thanks for all the info Bob, that is very helpful. Keep us posted of how the engine performs as it gets run in.

Edited By Piers Bowlan on 13/03/2017 19:21:40

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Piers this summer will be my fourth with this engine in this model, it has had about four gallons ( imperial ) through it at the moment, I bought this from a club mate who bought it new from a source here in Canada and he had bench run it only enough to break it in. I have tried several different size props of different brands and have settled on the master airscrew as the most appropriate for this model, l do not have a muffler fitted just the pipe it came with and 84db seems to be the norm at 10 feet and even less at the field boundary where local council bases its recommended sound levels.

Edited By Tony Richardson on 13/03/2017 21:59:36

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Thanks for the info chaps, very much appreciated and a decision is made, I'm having one!! I seem to be collecting projects again at the moment and the 1/4 scale Pilot Kit built Tiger Moth this engine is destined for is another. I met my old Tiger again last week, I built it whilst at uni in the winter of 1992, sold it on soon afterwards to raise funds for more beer!! I'd start a thread on its refurb but fear another unfinished thread might annoy more folk!

Thanks again chaps. How are they on fuel, what size tanks are you all using? I'd like long flight times.

Ian.

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Posted by reg shaw on 13/03/2017 22:10:12:

Thanks for the info chaps, very much appreciated and a decision is made, I'm having one!! I seem to be collecting projects again at the moment and the 1/4 scale Pilot Kit built Tiger Moth this engine is destined for is another. I met my old Tiger again last week, I built it whilst at uni in the winter of 1992, sold it on soon afterwards to raise funds for more beer!! I'd start a thread on its refurb but fear another unfinished thread might annoy more folk!

Thanks again chaps. How are they on fuel, what size tanks are you all using? I'd like long flight times.

Ian.

I don't think it's annoying watching one of your builds....finished or otherwise. Just great to see skills and techniques that other flyers use. Very interesting.

Crack on, Ian.

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  • 3 months later...

Screw the adaptor into the head as far as it will go without forcing it and dont use any thread lock as it just melts with the temps that four stroke heads reach, just a touch of oil on the thread .Back it off to the position you require and snug it up with spanner. Now run engine until nice and hot . Now tighten the locking nut firmly while hot. Use a good fitting spanner or you can distort the nut. If engine suffers from excessive vibration as some occasionally do despite balancing props etc then fabricate a support for the silencer that bolts to the silencer and engine mount. 

Edited By Engine Doctor on 03/07/2017 11:20:12

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I had a problem with the later machined alloy version that uses 3mm c/s allen screws, I think the key size is just too small to tighten them enough. I had planned to counterbore the alloy adaptor to take a standard size screwhead wich takes a larger allen key but sold the model before I could try it. The earlier brazed adaptor from JE used normal M3 allen screws and didn't come loose so I think the counterbore idea should work.

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Bert, in almost all the petrol engines I have experienced trouble with gaskets that would just disintegrate with heat. I stopped using them and instead now use high temperature RTV to form gaskets and that has worked perfect for me. Yes you will have to clean and reform every time you take the muffler down but I have seldom had that requirement after switching to the RTV

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Sorry to hear that Martin, you must have got one of those 4-00 pm Friday afternoon specials, there are 2/3 of these engines in our club plus a half dozen of its smaller brother the 30 four stroke and none have had that issue, sorry to hear that, they really are not a bad engine for the money.

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