Rcplanedan

Thats a strange place for a boxer aircraft engine!
would like to have a fan and some ducting for the engine, probably wouldn't like running on gas conversion with no cooling anyway....
ive seen rc cars with 4 stroke aircraft engines, but never noticed heli,s with one ,,something different

1967brutus

there absolutely is an engine-driven cooling fan, all the way at the bottom of the mechanics. It draws air through the ducting that is visible in the vid John posted, and discharges that air downwards. That cooling fan also contributes about 2 or 3 N (almost 5%) of the total lift generated...

And indeed, I don't think it would like a gas conversion... My fourstroke (vid posted earlier) allready ran CHT's well in excess of 150 deg C in normal flight, and a muffler temperature of around 400~450 degrees. Hot enough to let the aluminium my muffler was made of, sag...

Raleighcopter

it's probably not great to spin up that boxer without blades on the helicopter.

Rcplanedan

Rcplanedan

Could end with a failure like that one,

1967brutus

I advised him to keep it under 9K and that that prop was too light, but he insisted the manual allowed higher RPM than 9K...

EDIT: I see in the vid, that it even failed below 9K...

Rcplanedan

definitely an expensive lesson that one....i would have taken your advice for sure..the instructions are a little adventurous! I wouldn't like to be searching for spare parts for the engine these days.
that was definitely an interesting video to see

John_M_

Keep in mind that David had just completely dismanteled that engine just for a butchers prior to that disastrous video... he may have under torqued, or over torqued those rod cap screws... I think he just used an small allen key is all, finger tight... those cap screws are questionable in their spec out of the box, let alone taking one apart.

1967brutus

I have sought high and low, but never found torque specs other than "generic for the thread size" and without bolt material specs, that is a bit pointless. Hence my extreme hesitance to dismantle the engine further than the pistons off the rods. Crankcases are rare, rods also.

But I seem to remember that he made a video prior to the disaster vid, but post-reassembly, where he went to 9,5K
Andrew from JustEngines sternly warned me to keep it below 9K when I bought mine. Mine still lives after a LOT of use, having been broken in on gas and never seen anything else... I normally use the engine fairly moderately, but absolutely don't spare it when it has to do towing duty. Then it is full throttle all the way to 600 ft, multiple times in a row if needed..

Cat 1

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Teaser…Full report and video tonite. Air under wings

1967brutus

First impression, that thing runs BEAUTIFUL, Chris!

Yeeeee-Haw!

Cat 1

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Ok.. First impressions.

Plane flies beautifully - Well matched tot he power of the 1.60 - going to be one of those "go to" planes for everyday flying. Came out at 5.5KG (12lbs). I was close on my balance design estimate but had to add 100g to the tail so if I did it again I would push the tail back slighly.. but all up its a very nice plane to fly - Very "ugly stik" like. Nice presence in the air

Engine - almost enough power to pull vertical but not overpowered - 70+ deg climouts are slow - but in full control - For a quick tune the engine is running great. There are many parameters to play with with the solenoid curve the pump curve and the Air Bleed pressure. In the video I'm a bit rich at midrange. There is a "new" and unique characteristic with he "barf" tank is that the pressure is slower to respond when tank is low so it can get "lean" on a throttle application too quick and gets rich on a quick pull back - but engine stays running though those. I have some ideas to tune them out. Other than that change - the engine runs absolutely the same at full tank or empty, so the "uniflow" seems to work..

Spinning a 16X8 - both an APC wide and a MA classic.. The classic turns 8000 on the ground and might be approaching the "danger zone" in the air. (pass at 3:50 in video below). Have to get my telemetry setup working now.

8oz tank was lots (thanks Bert) as I flew for 15 minutes on a quite spirited flight with reserve. Cruising I think I could get 30+ as it flies well at low power settings.

With the big bore straight pipes the exhaust note is "crisp". Might have to consider some type of "can" but we don't have any noise issues where we fly.. Sounds very unique on approach where you only really hear one pipe.. Runs "clean" as the exhaust is directed to keep most of the splatter off the airframe.

Here is a quick flight.

https://www.youtube.com/watch?v=YQHt...ature=youtu.be

1967brutus

Naw... that is neither new nor unique... My .50 heli allready did that extremely noticable even without the solenoid and fuel curve. It is why I had to resort to an RPM governor, that would keep the throttle a bit more open during the rich seconds at pullback, and keep the throttle a bit more tempered at the lean periods after giving it a handful. Governor coped with that effortlessly (but of course, in those conditions, the load was controlled by the pitch commands.
But my engines do that also, albeit barely noticable, when the tank is near empty. A bit more slowdown on both up- and down-throttle cures it.

Edit: Having seen your vid: take it a bit easy at a cold start, Chris... Mine needs about 1 minute @ 3500 RPM, before the heads even get to 65 deg C. Starting it and giving it full throttle within 10 or 15 seconds causes extremely large temperature differences.
But it most definitely flies excellent and has a beautiful sound!

Glowgeek

Looking great Chris.

As Bert said, mine react more sluggish wrt to mixture changes, throttling up and down, once the tank is below 1/4 or so. Also, once you get that midrange leaned up a bit you will likely not be able to rev the engine as aggressively from a cold start. Mine take a while, as Bert said, about a minute before they'll rev normally.

Cat 1

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Great Advice Guys - I am usually a bit eager when it comes to that. It was however just running on the stand adjusting stuff - Got to get the telemetry working so as I can monitor closer..

Here is some "BARF trap action". Seems to work as intended.


While I have never noticed this before it stands to reason that a muffler pressure or tank pressure setup would react slower on an empty tank - the barf trap catches a lot more at empty by watching it - I assumed it was a reaction to the lines having to "clear out" and return the fuel to the tank. I think bigger lines here might be helpful.

I know some of my setup is probably not needed but as an experiment I thought it would be easier to install the full "setup" then work back by bypassing it. That way its all in there and an assessment can be made wether its worthwhile or not - I have a good baseline as it seems to work well in this full house configuration... By changing only lines I can revert back to any configuration setup

Cat 1

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Forgot to mention that it does catch the full volume even at empty tank. No overboard venting has been observed....

1967brutus

That's a very good way of documenting and for later analysis of events. Compliments!

John_M_

I agree, leave well enough alone... those are common allen head cap screws, probably no better in quality than what you can get from harbor freight... of course one hopes OS uses better spec'd screws... but dealing with such small fasteners, manufacture defects are more common... David's curiosity may have stressed an already defective screw... If I were to take one apart to that extent, I would replace those cap screws with some from an reputable source, possibly from an aircraft surplus supplier... it wouldn't take much rework to improve the reliability of those fasteners.




Nice job Cat... engine sounds good. 👍

1967brutus

I would concur... better to replace them with some high and known quality, than to re-use them bolts.

Glowgeek

I can't speak to ASP engine varieties but I have done complete overhauls on a half dozen OS and Saito boxers. Have yet to have rod cap issues/complaints from customers.......knock wood. I throughly clean the rod cap threading and torque using 100% castor for thread lube. I have little respect for that particular youtuber.

Cat 1

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Thanks John... think its going to be a keeper....

On the issue of "Aircraft Hardware" - Being in the industry I was surprised but some of the ratings and issues we see with Hardware.. Many industrial bolts (high grade cap screws) exceed any strength ratings of stuff available in the aviation streams - Its one of those monikers added to make people believe that "Aircraft Grade Fasteners" or Fords famous "Military Grade Aluminum" are much better than other items.. Most AN hardware has lower ratings than a grade 8 equivalent (or 12.9).. The only difference is the quality control of the aircraft stuff - But we see some real misses there also - machine screws without head recesses or threads are plentiful. The full on critical bolts are always tested and certified - But run of the mill fasteners are not - but everything is traceable to source... Not saying the aircraft stuff is junk - but its not guaranteed that its any better than good quality industrial hardware - in many cases its a lower rating strength wise.

That Said... we fly little airplanes so we should use little airplane bolts...

1967brutus

As you say, and there's the thing: it is about consistency, repeatability and tracability more than anything else. "Airraft grade" or "Mil Spec" are not about the quality itself but about the fact that the LEVEL of quality is known, constant and can be relied upon. At least, that is the theory.
It is a bit like that ISO9002 thing you see behind many company names. "ISO9002 certified"... That means something WRT quality, but not what the public thinks it means. What it means is that the level of quality control is documented, it does not mean that the quality is good.
If your company has a document somewhere that states that critical bolts are made out of chocolate and nuts out of cookie dough, then it can be ISO9002 certified as long as those items are actually made from said materials.

Now THOSE are wise words, Chris, again you dazzle us with your wisdom...

Cat 1

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Very well described Bert. Here is an example of what can go wrong. This one gave me sleepless nights as my Son flys the “Bell mediums” like the one that went down and we also had a medium in the air when the initial AD came down -with recently changed pins…

https://www.tsb.gc.ca/eng/rapports-r.../a21w0045.html

How this could happen on a super critical piece such as this shows how the systems can fail. How this could happen given the depth of control systems to stop this type of thing is mind boggling. I know engineers that now check every critical part with a magnet -and will for the rest of their careers -

1967brutus

A horrible story to read...Especially the fact that numerous steps in the entire process Could, but above all SHOULD have identified the sub-spec parts, but failed to do so for about 25% of the parts.
But here's the thing: THAT is why such systems are in place, to trace back where it went wrong, and at exactly that tracability, the actual manufacturer of those pins failed to provide tracability (the helpers who messed up could not be identified).
Meagre solace for the pilot and his family, but that FMC company at least has been weeded out from the process, and rightfully so....

Raleighcopter

My last company, Gannett Fleming was iso 9001 certified (also quality related). They had more quality related paperwork and processes than I have ever experienced. They also had an entire company of employees who had figured out how to fake actually doing those quality procedures. In fact, in many cases they skipped quality all together and just filled out the forms. The place was filled with unqualified reviewers who were fine with falsifying forms so they could claim they met the quality requirements when the annual audit came around and auditors didn't look at actual work product, just forms.

They were responsible for dropping a 22 thousand pound slab of concrete on a car during "the big dig" project in Boston and they did the inspection on the bridge that collapsed in Pennsylvania a few years back. Still, they were iso9001