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Author Topic: Hot start OS FP 20 ABN  (Read 1484 times)

Offline Joe Ed Pederson

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Hot start OS FP 20 ABN
« on: September 08, 2021, 08:27:15 AM »
I have two OS Max FP .20 ABN engines.  Both start on the second flip when stone cold.  But they need 30 minutes to cool down after a run before I can flip start them.  Less than 30 minutes and it takes an electric starter and even with the electric starter they don't start quickly.
 
One of them I bought "new" and it has a couple of hours of run time.  The other one I bought used, but while they are still hot (less than 5 minutes after a run) they both seem to have a lot less compression than when stone cold. 

I'm using 10% nitro, and 20 % oil (50% syn, 50% castor.)  Both are running an APC 9 x 4 prop and launch rpm is 11,600 to 11,700.

Is it normal for the FP series to need to cool down to room temperature to be able to flip start? 

Thanks,
Joe Ed Pederson

Offline Brad LaPointe

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Re: Hot start OS FP 20 ABN
« Reply #1 on: September 08, 2021, 08:59:54 AM »
Hot weather and mufflers are the enemy of restarts . My suggestion is that you bring out two models and alternate back and forth. This is also a good time to bring along the test stand and break ( run ) in that new motor .

 Years of using LA .25’s for sport race and combat tells me that each engine has its own “personality “ . Quick restarts take practice . The only way to quickly cool down an engine is some kind of external physical agent. Fuel ,water, F-1 uses dry ice . Easier to let nature do it’s thing .

Brad

Online Brett Buck

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Re: Hot start OS FP 20 ABN
« Reply #2 on: September 08, 2021, 09:47:14 AM »
Is it normal for the FP series to need to cool down to room temperature to be able to flip start? 

   No, mine hot-start just fine. I strongly suspect it is technique - very likely, over-choking. If you over-choke, raw fuel gets on the piston, causes it to shrink, the cylinder is still hot, so no compression.

   Mine start right away - when hot, one pull through with my finger over the venturi, remove and immediately flip forward. Note that this has to be *immediately*. All that pull is for is to get fuel up to the venturi.  Any more, and its too much, wait too long and runs back in the tank. If you then correctly diagnose that it didn't get enough fuel, and pull it through 3-4 times - cold fuel on piston, and endless flipping.

    This is not unique to FPs - same thing happens with PA, RO-Jett, etc.

     Brett

Offline Joe Ed Pederson

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Re: Hot start OS FP 20 ABN
« Reply #3 on: September 08, 2021, 10:08:23 AM »
Hot weather and mufflers are the enemy of restarts . My suggestion is that you bring out two models and alternate back and forth.

Brad

 Thanks, Brad.     I wish I could fly two models alternately.  I have more than two.    But my practice field doesn't have room for two circles and each plane has it's own set of lines/handle.   I could reel in the lines for the model I just flew and reel out the lines for the next model, but that strikes me as too much trouble.

Joe Ed

Offline Joe Ed Pederson

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Re: Hot start OS FP 20 ABN
« Reply #4 on: September 08, 2021, 10:13:51 AM »
   No, mine hot-start just fine. I strongly suspect it is technique - very likely, over-choking. If you over-choke, raw fuel gets on the piston, causes it to shrink, the cylinder is still hot, so no compression.

     Brett

Brett,

Guilty as charged.  I have been pulling through three blades of choke whether hot or cold.

I will definitely try your approach of just bringing the fuel up to the venturi when hot and immediately flipping to start.

Thanks,
Joe Ed


Online Brett Buck

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Re: Hot start OS FP 20 ABN
« Reply #5 on: September 08, 2021, 11:31:02 AM »
Brett,

Guilty as charged.  I have been pulling through three blades of choke whether hot or cold.

I will definitely try your approach of just bringing the fuel up to the venturi when hot and immediately flipping to start.

Thanks,
Joe Ed

   If it is on a profile, just watch the fuel in the line, and pull through just until it gets to the spraybar, then remove finger and flip forward  immediately.

   Brett

Offline Joe Ed Pederson

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Re: Hot start OS FP 20 ABN
« Reply #6 on: September 08, 2021, 01:20:18 PM »
Brett,

Yes.  It's on a Skyray .35 built as you describe.   I'll watch the fuel line for the fuel coming up to the spraybar and flip immediately.

Joe Ed

Offline Tim Wescott

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Re: Hot start OS FP 20 ABN
« Reply #7 on: September 08, 2021, 03:47:09 PM »
Yes.  It's on a Skyray .35 built as you describe.   I'll watch the fuel line for the fuel coming up to the spraybar and flip immediately.

What Brett said -- but I'll add that you need to develop the right touch.  I understood the theory of this for quite a while before I got the practice down to where it actually worked for me.  If Brett says it's easy -- he's an engine whisperer.  Just keep trying, you'll get there.

If you do screw it up and you're desperate, try some fuel on the cylinder fins.  That may cool it down quicker, and probably won't harm anything.  Maybe.  Probably.  Or if you're not at a contest, just take some time out to do something else for a bit.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Tim Wescott

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Re: Hot start OS FP 20 ABN
« Reply #8 on: September 08, 2021, 04:39:22 PM »
They're not exactly fit like a Pico or Rossi. Those engines are fit for RC fliers that take them out of the box and bore a hole in the sky with who knows how much nitro. Could be too loose from new. Lucky if you get one that's tight for CL stunt work.  I think you're a little past the break in period at 2 hrs. not going to get better, might even have peeled lining by now.

If I had two like that and they weren't peeling, I would take both piston and sleeves out and send them to www.rayaracing.com and get them pinched. The only other thing would be to see how the bigger of the two pistons feels in the smaller of the sleeves and also use the best two wrist pin pads to make one good engine if you have those skills.

Motorman 8)   

If it's broke, I can fix it, if it ain't broke, I can fix that?

All of the ABN OS FP and LA engines have worked this way for me, while at the same time being reliable runners in general.  I don't think I'd want to mess with 'em.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Paul Smith

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Re: Hot start OS FP 20 ABN
« Reply #9 on: September 08, 2021, 05:34:27 PM »
You buy an electric starter and battery for less than an engine.  If the starter doesn't work, the engine is probably used up and needs to be swapped-out for a  good one.
Paul Smith

Offline Brian Hampton

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Re: Hot start OS FP 20 ABN
« Reply #10 on: September 08, 2021, 08:14:18 PM »
I have two OS Max FP .20 ABN engines.  Both start on the second flip when stone cold.  But they need 30 minutes to cool down after a run before I can flip start them.  Less than 30 minutes and it takes an electric starter and even with the electric starter they don't start quickly.
I had (have) a similar problem with the red head (ABC) version of my Enya 61CXLS. Nice pinch when cold but on its first run after it stopped I gave it a quick flip and almost no compression and impossible to restart until it cooled to barely warm and compression had returned. Fuel used was my usual 25% castor no nitro and I've never experienced this with any other engine. Eventually I sent the piston/liner back to Enya who sent me, free of charge, a replacement. Fractionally better but still hopeless for hot restarts so it's been relegated back to the box it came in.

There's one thing I still intend to try and that's to see if the head from my earlier model ringed CXLRS will fit. That head and button are finned while the later red head has no head fins. My reasoning is that possibly the unfinned head gets much hotter and differential expansion rates between the head and liner causes the clamping pressure from the head bolts to pull the top of the liner away from the piston.

Online Brett Buck

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Re: Hot start OS FP 20 ABN
« Reply #11 on: September 08, 2021, 10:08:33 PM »
They're not exactly fit like a Pico or Rossi. Those engines are fit for RC fliers that take them out of the box and bore a hole in the sky with who knows how much nitro. Could be too loose from new. Lucky if you get one that's tight for CL stunt work.  I think you're a little past the break in period at 2 hrs. not going to get better, might even have peeled lining by now.

  I assume this is all well-intended, but you are right about the fit - it fits *better* than a Picco or a Rossi for our purposes. It's not peeled, it's not a matter of luck if you get a good one, it is a *far superior* fit for CL stunt purposes, and *far superior* in that regard to almost any CL engine ever produced by a major manufacturer.

   We - if we are smart - run it almost exactly like those RC sport fliers and trouble-free "boring holes in the sky" is *exactly what we want from a stunt engine*! It was designed to do precisely what we need.

   Joe Ed has a minor technique problem that he can fix in about 5 minutes by doing something slightly differently -  and now we are talking about "peeling liners"  and completely unnecessary radical "fixes"! Oy Gevalt!

    Brett

Offline Gary Dowler

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Re: Hot start OS FP 20 ABN
« Reply #12 on: September 10, 2021, 08:52:50 PM »
This is interesting.  While my two FP's on profile ships restart fine, where this might help me is with my Fox 35 on my Cobra.   Starts very well the first flight, and runs beautifully after Paul helped walk me through shimming the intake port.  But subsequent flights see starts that are time consuming.  Still runs great once going, its just getting it to that point.  Second flight takes a minute or two of flipping, third flight is worse yet.  I don't like to use my electric starter on it, especially since it has a prop shaft extension,  but the endless flipping gets tiring and time consuming.
An idea I came up with, and might try next time out, is to take a battery powered Coleman air inflator for an air mattress with me.  I can set it to just blow air over the motor for a minute or two after each flight and see if that aids the process.
I plan to try Brett's suggestions on technique first, with the cooling air idea in reserve.
Gary
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Online Dan McEntee

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Re: Hot start OS FP 20 ABN
« Reply #13 on: September 10, 2021, 09:10:47 PM »
  One problem with restarting hot, especially fox .35s, is that the head and cylinder temperatures soak down to the crankshaft pretty quickly and any fuel padding through the crankshaft can boil. Just try dropping a few drops of fuel on the crank case when the engine stops running and watch it boil right off.  When I first tried Fox Racing at the SIG contest, I had trouble restarting hot engines just like everyone else. I would see guys dump a syringe of fuel on the cylinder to cool it off, and while this worked, my first thought was "fuel is expensive!" and my second thought was "water had a higher boiling point and will chill faster!", so I started to take a syringe of ice water along to pit with and dumped it on the bottom end of the crank case. This worked better and I often got one or two flip starts at pit stops with REAL stock .Fox .35's !!  If you are careful with it it doesn't make a big mess!!
   Type at you later,
    Dan McEntee
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Online Brett Buck

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Re: Hot start OS FP 20 ABN
« Reply #14 on: September 10, 2021, 11:15:58 PM »
This is interesting.  While my two FP's on profile ships restart fine, where this might help me is with my Fox 35 on my Cobra.   Starts very well the first flight, and runs beautifully after Paul helped walk me through shimming the intake port.  But subsequent flights see starts that are time consuming. 

       I got to the point of being able to hot start my Foxes very reliably. I don't guarantee results but, this is in a Nobler, cylinder down. Attach battery, pull through forward with choke, finger completely covering the intake. Keep pulling through forward with finger over until you get one bump. The, immediately, flip forward while removing your finger. If you don't do it fast enough, or you pull your finger too soon, you will get too much (not fast enough) or, not enough (too soon).

    If you do get too much, take out the glow plug, flip it over forward a bunch of times, put the plug back in, then attach battery and flip forward.

   It doesn't work on a profile (but what are you using a Fox on a profile for?) and I have all sorts of problems getting all types of engines started, hot or cold, when mounted upright.

  I think the only reason this works on a Fox is that the intake stack is short enough that it doesn't hold a lot of fuel. When I first got my ST46, I tried the same technique, and when I went to flip it, I almost broke my finger, because it was hopelessly flooded to the point of hydraulic lock.

    Note that this was, to my astonishment, *40+ years ago*, but my condition makes me recall it like yesterday, and physics and chemistry haven't changed too much since 1978. 

    In all these cases for hot starts, the critical matter is to get *just enough* fuel in the engine to get it to bump without getting too much. The tolerance for "too much" is nearly zero, even a little bit over with some engines, and you are in trouble. The Fox is particularly tricky and notorious for bad hot-starts, but I that is all I flew back in the day and got flight-after-flight-after-flight as fast as I could put in the fuel, and, I couldn't flip it over if necessary because I was using a stooge.

   With big ABC/AAC engines I never ever flip them forward with the battery attached, but I it safe enough with the Fox and a wood prop. Back-bumping is the only safe way to start them with your fingers, and it also has a lot more tolerance to excess fuel, because it blows the excess backward out the venturi. Even a pretty good Fox tends to have such low compression that it doesn't easily fire off with a back-bump.

      In almost all cases, the trick is to get just the right amount of fuel

     Brett

Offline Gary Dowler

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Re: Hot start OS FP 20 ABN
« Reply #15 on: September 11, 2021, 12:53:02 AM »
Brett, cant thank you enough.  Ive copied and pasted this to the notes on my phone, and will try on my next outing, which I hope will be in the next few days.  If I get out, Ill post a proper after action report on the result.

Gary
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Offline Gary Dowler

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Re: Hot start OS FP 20 ABN
« Reply #16 on: September 25, 2021, 03:37:05 AM »
Brett, I finally got a chance yesterday to get out, however briefly.  Your suggestions on hot starts with the Fox we’re very helpful.   Can’t say my results were perfect, but second flight was ready to go much faster than has been the case. I’m sure it’s just perfecting the technique at this point. 
A couple more patterns in the books, however rough they may have been…..lol

Gary
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Offline Mike Urban

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Re: Hot start OS FP 20 ABN
« Reply #17 on: November 17, 2021, 05:49:34 AM »
I learned a trick from Pat Willcox, watching him pit Fox 35’s in speed limit combat. In addition to the syringe full of water, which is dumped right on the cylinder, lay a few drops of light machine oil on the piston through the exhaust port. The compression comes right back. Doesn’t work if you’re using a muffler, but this was unmuzzled competition.

Offline phil c

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Re: Hot start OS FP 20 ABN
« Reply #18 on: November 20, 2021, 04:22:06 PM »
I had (have) a similar problem with the red head (ABC) version of my Enya 61CXLS. Nice pinch when cold but on its first run after it stopped I gave it a quick flip and almost no compression and impossible to restart until it cooled to barely warm and compression had returned. Fuel used was my usual 25% castor no nitro and I've never experienced this with any other engine. Eventually I sent the piston/liner back to Enya who sent me, free of charge, a replacement. Fractionally better but still hopeless for hot restarts so it's been relegated back to the box it came in.

There's one thing I still intend to try and that's to see if the head from my earlier model ringed CXLRS will fit. That head and button are finned while the later red head has no head fins. My reasoning is that possibly the unfinned head gets much hotter and differential expansion rates between the head and liner causes the clamping pressure from the head bolts to pull the top of the liner away from the piston.

If the older engine hot restarts I think the head-finless engine has the problem.  If the finned head works that solves the problem.  If not theen it is maybe too loose a fit between the piston/liner/taper, the  liner/case, or the piston/liner/case materials aren't matched too well.
phil Cartier

Offline phil c

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Re: Hot start OS FP 20 ABN
« Reply #19 on: November 20, 2021, 04:31:06 PM »
I have two OS Max FP .20 ABN engines.  Both start on the second flip when stone cold.  But they need 30 minutes to cool down after a run before I can flip start them.  Less than 30 minutes and it takes an electric starter and even with the electric starter they don't start quickly.
 
One of them I bought "new" and it has a couple of hours of run time.  The other one I bought used, but while they are still hot (less than 5 minutes after a run) they both seem to have a lot less compression than when stone cold. 

I'm using 10% nitro, and 20 % oil (50% syn, 50% castor.)  Both are running an APC 9 x 4 prop and launch rpm is 11,600 to 11,700.

Is it normal for the FP series to need to cool down to room temperature to be able to flip start? 

Thanks,
Joe Ed Pederson
The ABN 20-25's all should hot restart with one or two flips if they didn't overheat from a too lean setting.  Either way they should hot restart IF, as Brett says, they got too big a prime.  We've been using both the FP20 and 25 and LA25 in combat  flying for years.  Even well used ones still start one flip when hot, if they haven't gotten too much fuel.
If they have, as Paul said, cool them off.  Easiest is to shut the exhaust and douse the cylinder and head with water.  Fuel can cause fires.
phil Cartier

Offline Joe Ed Pederson

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Re: Hot start OS FP 20 ABN
« Reply #20 on: December 03, 2021, 05:21:32 PM »
Well, I got to fly for the first time since late September and flew 4 flights on my Skyray .35 with the FP .20 ABN.  It got to near 80 degrees here today.

I had two hot starts and both hot starts took one flip.  On the first hot start, just filling the uniflow clunk tank sent fuel up to the NVA, so I just hooked up the glow driver and off she went on the first flip.  On the second hat start, I drew fuel up to the NVA slowly, and again off she went on the first flip.

I also had 4 flights on the box stock Banshee I bought from a club member when I first got back into CL about 3 years ago.  It came with a Fox .35 that I added the bypass plug to keep from having the Fox burp.  I had one hot start with it today and the same technique got a single flip start as well.

Thanks again everyone for the suggestions, especially to the engine whisperer, Brett Buck.

Joe Ed Pederson



 


Online Brett Buck

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Re: Hot start OS FP 20 ABN
« Reply #21 on: December 03, 2021, 06:45:01 PM »

Thanks again everyone for the suggestions, especially to the engine whisperer, Brett Buck.

  Glad it worked!  As always, I do not consider myself an engine expert. But I have done this long enough to have *made nearly every possible mistake* and due to my unfortunate condition, remember *every single one of them*!

    Brett

Offline Daniel_Munro

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Re: Hot start OS FP 20 ABN
« Reply #22 on: December 06, 2021, 10:13:29 PM »
I used to have similar issues with an LA25. Found the best way is to refuel, DO NOT prime. Just turn the glow on and smack the prop. It should fire up.
NZL7396

Online Brett Buck

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Re: Hot start OS FP 20 ABN
« Reply #23 on: December 06, 2021, 11:24:39 PM »
I used to have similar issues with an LA25. Found the best way is to refuel, DO NOT prime. Just turn the glow on and smack the prop. It should fire up.

    That works pretty good if the fuel line runs keep fuel in the line after you fuel it up, that is, it goes under the engine or is about level. All of mine have a problem when the fuel line is on top (like a profile with the stock rear needle), because while fueling it pushes fuel up the spigot, it all runs back from gravity. It won't usually run on the prime long enough to suck the fuel all the way to the spigot before it quits.

   You really don't want/need any significant prime to get into the engine, but you do need it pretty close to the engine.

    Brett


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