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Author Topic: Engines for Slow Open Power  (Read 5589 times)
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RobinB
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« Reply #25 on: September 15, 2009, 07:38:25 AM »

I emailed Chris Murphy, who's my usual source of info on engines. He replied that he had one (also without paperwork) which he'd received as a wedding present from Dave Hipperson!

When I've got a spare evening to listen to Dave ;-) I'll try to find out more.

I may get to run it this weekend when I'm at Merryfield.

Somehow I don't think I'll flick this one - I can scarcely turn it over as it's brand new.
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applehoney
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« Reply #26 on: September 15, 2009, 09:33:40 AM »

When I've got a spare evening to listen to Dave ;-)  I'll try to find out more.

Give Dave and Sue my best when you do? Long time no hear....
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PeeTee
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« Reply #27 on: September 15, 2009, 09:58:35 AM »

Dave & Sue came to a FF comp for the first time in yonks - the Southern Gala at Little Rissington a couple of weeks ago. They were acting as J O'D's fetchermite & time keeper respectively!
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applehoney
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« Reply #28 on: September 15, 2009, 11:26:28 AM »

Encouraging...

I only timed for J O'D once, at a Winter Rally. After standing in a freezing wind for 40 minutes holding his glider, waiting for him to signal a launch, I vowed 'never again'. He maxed, of course ....
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RobinB
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« Reply #29 on: January 18, 2010, 11:06:39 AM »

I just dug out a Cox TD15 which I got from a club mate donkeys years ago, and I've never used. Before deciding whether to sell it or use it I thought I'd better give it a run on the test stand. Cleaned the ancient gunk out of the carb and checked that the plug was ok, and then spun it up.

It fired on a prime but wouldn't run after that. It didn't seem to be drawing in enough fuel, even with the needle almost falling out of the spraybar.

I messed around with tank height but it didn't help.
Then I remembered to check if it had been run on pressure before, and found that it had. Plugging the pressure takeoff got it running , but still a bit unresponsive to needle adjustments. Then I remembered John B. saying that it would like 30% nitro, and I was using 15%. Time to get some more nitro. (And also replace that annoying screw-head prop retaining bolt!).

Anyway, the ongoing problem I have is this: how do I keep anything attached to that little pressure nipple? Every bit of plugged pipe I've used has vibrated and/or slipped off. What sticks to Cox black Delrin? Anything?

Robin
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danberry
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« Reply #30 on: January 18, 2010, 11:16:09 AM »

You very likely have gunk in at least one venturi orifice. Pop the venturi, remove the needle and do some soaking and poking (careful poking) to clear them.

The old hard clear plastic might be the best best for that nipple. Or backfill it with epoxy.
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glidermaster
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« Reply #31 on: January 18, 2010, 01:55:26 PM »

Hi Robin,

Dan's right, make sure all the little holes in the venturi are clear.

So far as the pressure tap is concerned, I would dismantle the engine, and put a small plug into the hole in the crankcase material - i.e. in the main bearing area. A 10BA countersunk screw would be my choice - make it short so that it doesn't go through into the main bearing. The countersink head will retain it and stop it vibrating into the engine. Be scrupulously clean with any swarf, of course, and seal with thread seal or some such when you finally install it. Clean up the outside with a fine file so that the plastic cover will go back on. No need to worry about the hole in the plastic housing then, of course.

Check on eBay; there's a guy selling all sorts of neat after market parts for TDs including the 15, and he makes a pressure tapped backplate for the 15, although putting a nipple into the original backplate is not too hard.

Also, check with Mike Wills (if you can find him) - he had someone put a Nelson plug into a burnt out TD 15 head - definitely the way to go.

John
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RobinB
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« Reply #32 on: January 20, 2010, 04:35:30 AM »

John, Dan, the holes are clear ok.

I couldn't get the black housing to come off and didn't like to get over-persuasive with it in case I damaged the seal. Instead, I cut away the plastic round the hole, cleaned the metal and put a blob of JB Weld over it. I'll see if that holds - that stuff is usually ok on clean metal.

I know the website you mentioned - I got a TD049 housing from there a while back. It's for the engine I bought new and then lent to
Derek Wain for his 1/2A model. Housing had split in the usual place. I should get round to sorting that one out soon.

I also need to sort out the tank mount on my test stand - the old rubber band bodge-up can't cope with the Cox vibrations!

Thanks, Robin
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applehoney
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« Reply #33 on: January 20, 2010, 10:33:08 AM »

You've sealed off the pressure nipple - good move. Forget a pressure backplate tap and use a pacifier/surgical tubing tank. No more feed problems and a reliable run
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danberry
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« Reply #34 on: January 20, 2010, 11:43:05 AM »

Sealing the case is a good start.

You described a fuel-flow problem. If the needle and orifice are clear, then it must be a problem with tank height, length of fuel line or a venturi that is bored out for pressure. I don't know the stock hole diameter. The pressure tap being opened is a red flag for too much venturi opening to draw fuel. Try a bladder (not the Haggis kind).

20% all castor oil is a good idea.
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RobinB
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« Reply #35 on: January 20, 2010, 12:13:06 PM »

Thanks for your comments, gents. I certainly wasn't going to bother with an alternative pressure tapping - too much plumbing.

George Fuller converted me to the joys of latex (!) some while ago.

Now the engine is a bit cosmetically-challenged I'll probably be keeping it rather than sell it. Can't use it in SLOP with pressure feed, so it'll be in a Classic model. Where's that Creep plan Jim sent me? Smiley

Prop :- 7x4 or 8x4?

Robin
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glidermaster
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« Reply #36 on: January 20, 2010, 06:09:33 PM »

Try 7.5x4 - but start with an 8x4 and cut down - don't stick bits onto a 7x4 - I found that they come off (to almost quote the illustrious Ray Moore)!

If I remember the 60's correctly, the 'normal' prop for TD 15 was an 8x4, but it really is a bit too much for a 15. My OS15FP seems to like a Master 8x4 cut down to 7.5.

John
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danberry
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« Reply #37 on: January 20, 2010, 07:03:17 PM »

Yeah, adding to the prop is a bad idea.

Venturis shouldn't be too hard to get. Or try a bit of restrictor.

Does the slow event have a rpm limit? If so, I'm trying to fathom why forcing bad fuel flow onto a flyer came about.
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glidermaster
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« Reply #38 on: January 21, 2010, 10:46:59 AM »

No, Dan, there is no RPM limit.

Slow Rules;
3.5cc max engine size - plain bearing engines only.
No auto surfaces other than DT - including no folding prop.
Suction fuel feed only, fuel cut-off only, and no brakes.
No weight limit, no size limit.
10 secs engine run for glow engines, 12 for diesels (3 minute max.)

(Did I forget anything?)

John
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danberry
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« Reply #39 on: January 21, 2010, 01:53:01 PM »

Aha!

The diesel looks to have a distinct advantage in the event.
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RobinB
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« Reply #40 on: January 21, 2010, 03:22:11 PM »

Dan, you're right - the diesel-powered models have been successful in the class. Most popular diesel is the PAW19 CT3, partly because it's fairly powerful but also because it's about the only suitable engine still being made. It doesn't have the thrust / weight ratio of many glow motors, but the extra 2 seconds of motor run help!
It has been regularly suggested to the Free Flight Technical Committee, who make the rules, that pressure feed systems be allowed. They consider it, but don't change the rules.

However the same body introduced the Classic Power class a few years ago and allow any engine and fuel system. (And a 12 second run - diesel or glow).

So, if you want to fly a modern fixed-surface SLOP model you have to have a gravity-fed system. But if your engine needs a pressure system to get a clean run then you have to put it in a pre-1961 model, or fly it as a BMFA Power model (fixed surfaces any engine any fuel system 9 sec*. run).

Did I mention that we also have a Restricted Technology Power class now? Perhaps I'll leave that for another day!

* It's 9 seconds this month, but could change again Huh

Robin
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danberry
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« Reply #41 on: January 21, 2010, 07:57:33 PM »

Robin, you've rattled off a lot of events.

I note the engine runs. What are the maxes for each? Does the engine run reduce at some point?

Over here, most of the country flys at Cat3 --- 2 mins at 7 secs X 3, 2mins at 5 secs X 2, the 2/5 mins at 4 secs until you drop.
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« Reply #42 on: January 22, 2010, 03:28:36 AM »

Dan

I'm not Robin (& certainly not Robin Hood Grin), but as I'm sitting at the keyboard I'll give you the information as best I can.

The classes Robin mentions all have a 2 1/2 min max for the specified motor runs. There are normally 3 flights, plus an unlimited fly-off for those who max out. For major centralised meetings (e.g our FF Nats in May) the CDs have some freedom, and if the weather is good, may increase the max to 3 mins. On the other hand, if it's really windy, it can come down to 2 minutes. This was the case at the Nats a couple of years ago, when 2 1/2 mins took you over the hills & far away - good job I was only flying CLG on that day!

Cheers

Peter

edit - I'd not spotted Restricted Technology, which is F1C lite, and will be flown to 3 min maxes I believe
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glidermaster
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« Reply #43 on: January 22, 2010, 03:28:07 PM »

It is rather odd that the BMFA has these variations on the max, but doesn't compensate engine run-wise. If you're going to fly to a 2 min. max on a windy day, knocking at least a couple of seconds off the run would seem sensible (to me, at least).

I was just browsing eBay again, and saw that the guy making handy-dandy parts for various Coxes now offers a machined carb body for the TD15 - $25 - not bad, really.

Are you building anything yet, Robin?

John
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glidermaster
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« Reply #44 on: January 22, 2010, 03:40:11 PM »

I should have tacked this onto the last message, but anyway......

I have been corresponding with John Thompson in the UK, and he's taken to the Classic Power and Vintage FAI Power thing more than just about anyone I've heard of, hanging up (figuratively) his foil winged F1Cs in the process. Stopping the F1C flying obviously rendered a Nelson or 2 spare, so what better way of using one than to put it in a Classic model - in his case a FAI size Jaysbird. No systems (other than pressure), an APC prop, and apparently it climbs to about 1100 feet. He described it as a model that is not for the faint of heart!

To use an English phrase, it's not really cricket, is it?
John
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RobinB
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« Reply #45 on: February 01, 2010, 06:20:26 AM »

Are you building anything yet, Robin?
John

John, I still have to get the Lucky Lindy finished, having decided to put an OS20FP in it. I also have 2 SLOP aeroplanes in progress. Originally, they were going to be about 400 sq.in. for PAW19 DS4 engines. However, the wings came out a bit too over-engineered (i.e. heavy!) so I cut out the bad bits and am now making extra centre panels for them, the idea being that they'll be bigger but lighter for their area. The DS4s have been sold and I'll now use PAW CT3s instead. That's the plan, anyway, but I'm currently using all my workspace on a foam cutting project making some sample templates and wing building supports for the local model shop.

I'll do some pics asap and put them in the Power model thread.
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craig h
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« Reply #46 on: February 01, 2010, 06:57:40 PM »

What about a Fox .15X ? I know this is a nostalgia legal engine but could it still be used in the Slow Open Power? And what design model would be a good match for such an engine.... couldn't you use a nostalgia design and use it in two different events?
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« Reply #47 on: February 02, 2010, 11:45:17 AM »

Craig, to answer your question about the Fox 15x and what planes to use for both SOP and Nostalgia. If you kept the wing area under 400 sq. inches the Fox would probably be ok. The Zeek, Kiwi A, Fubar, and Top Banana would be good choices to fly in SOP and Nos. "A" gas.

Scott
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RobinB
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« Reply #48 on: February 03, 2010, 07:15:44 AM »

UK SLOP flyer Dave Clarkson had a Fox 15 in one of his models. He had to mount the tank right next to the (sidewinder-mounted) engine.
Robin
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glidermaster
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« Reply #49 on: February 03, 2010, 01:26:28 PM »

I think the Fox would be quite a good choice for SOP - they're light, and respond well to nitro. There are various versions, of course, though I don't claim to know one from another. They are plentiful on eBay I observe, and I think they are fairly 'affordable'.

A Fox 15 in a Dixielander would be a good combination. Sub 13 oz. would be a distinct possibility.

John
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