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Author Topic: Engines for Slow Open Power  (Read 5591 times)
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faif2d
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« Reply #50 on: February 03, 2010, 04:53:51 PM »

Look for one of the XX versions. It was faster and will live longer.
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RobinB
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« Reply #51 on: August 11, 2010, 03:50:31 AM »

Update on the TD 15 'struggle' :- found some time to get to Sundays Area Event, and ran the Cox again.

On pressure and 25% nitro it ran clean and fast. Had it in a test stand mounted on a short plank of wood, so I could wave it around while it was running. (Anyone seeing me do this would have wondered what the hell I was doing!). Gave it a couple of runs like this, fueled it up for a third run and it wouldn't start. Plug had gone open circuit, and I have no replacement heads left. This was annoying, especially as ,having been advised to keep the plug voltage as low as possible, I'd checked that it was no more than cherry red. Clubmate Mike Wills advised getting the head converted to take a separate plug.

Anyone else had this happen? Any suggestions?
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Pit
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« Reply #52 on: August 11, 2010, 07:09:39 AM »

The idea for conversion to a standard glow plug is the best all-around solution. There was/is someone in the States who does such conversions, but I can't remember who (Eric Clutton aka Dr. Diesel?). OR, you can try here for replacement heads: http://coxengines.ca/. You might also check with RJL Industries http://www.mecoa.com/acc/index.htm (in stock).
« Last Edit: August 11, 2010, 08:21:37 AM by Pit » Logged

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Scottl0413
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« Reply #53 on: August 11, 2010, 09:39:29 AM »

Robin, sorry to read about your glow plug issues. If you're burning out glow plugs on 25% nitro it sounds like you're running to high on the compression scale. I would suggest adding another head shim to reduce the compression a little. This is common practice as you go up in nitro %.

Scott
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RobinB
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« Reply #54 on: August 11, 2010, 10:42:54 AM »

Thanks, Scott. That's the first time anyone's suggested that.
I didn't think 25% was unusual for these engines, so assumed it wouldn't be a problem.

I can get the head drilled and tapped for a plug, but does anyone know if there's more to it than that?
(I suspect there is Angry )

Robin
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« Reply #55 on: August 11, 2010, 11:03:36 AM »

Mostly just using the proper "reach" plug. I think the stock head, when milled for the seat, will only take a short plug.
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« Reply #56 on: August 11, 2010, 11:34:16 AM »

Robin, 25% nitro shouldn't be a problem with the standard glow head, but the symptoms point me to that conclusion. Give it a try and find out! I run 35% on my TD 09's and I think I have two head shims it them and I have yet to burn up a glow head.

Scott
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applehoney
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« Reply #57 on: August 11, 2010, 11:43:10 AM »

35% doesn't hack it for a Cox, they love nitro. I run 60% - 65% in my .09's, .049's and .020 with just the one head shim - rarely lose a head and even then mostly with the .049's.

Balljoints have to be reset periodically.
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glidermaster
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« Reply #58 on: August 11, 2010, 02:12:29 PM »

The best option, Robin, is to get the burnt out head drilled for a Nelson plug. I think Mike (Wills) had this done for at least one of his engines by Ed Needham. Alternatively Bob Mattes in the U.S. can do it. Actually Mike had a very good 'friendly' machinist local to him who made various bits. Bob Mattes is very good, but he doesn't do it for nothing.

There are alternatives to the Nelson plug, from Rossi and OS - known as Turbo plugs, like the Nelson they seal on a conical seat at the base, rather than a sealing washer like a normal glow plug. Performance will be as good or better than a std. Tee Dee head with a Nelson plug.

I somewhat agree with Jim, a bit more nitro is in order. The killer with Tee Dee heads (or any head come to that) is running lean. Too little nitro can encourage lean running as the engine will sound rich (crackly). When you lean it in to get rid of the crackling you can find you've killed the head. It's all very well recommending 60 to 65% nitro, and Jim's right, they do like it, but it can be difficult to get, and engines can be difficult to start on it. I recommend 40% and 50% as the max.

John
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danberry
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« Reply #59 on: August 11, 2010, 07:15:48 PM »

Lower the compression with a gasket.

One issue with drilling the glow head for a regular plug is the softness of the original glow head.

What prop are you running?
Remember to use castor oil in that fuel.
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RobinB
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« Reply #60 on: August 12, 2010, 05:46:02 PM »

Thanks for all this info - wish I'd known earlier Sad . From what you say, John, it sounds as though lean running might have been the problem.

I'm making inquiries about having the head converted, but will also shop around for some more heads.

Dan, I was running it on a thin-bladed 8 x 4.

I'll let you know how it all ends up

Robin
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« Reply #61 on: August 12, 2010, 05:54:45 PM »

8x4 is good. If you'd said 6x4 , well, anyway.

Secure mounting is important. They do vibrate a lot and that can affect plugs.
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glidermaster
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« Reply #62 on: August 12, 2010, 06:58:51 PM »

MECOA list a plug adapter head for Cox 15 - $15. It suits a K&B 1L plug but would be OK for a Taylor, too. They show it as suitable for the Medallion and TD 15 which I'm not sure about. The original Cox heads for Medallion and TD were different in combustion chamber contour.

An alternative, if you have a lathe or friendly lathe owner, would be to machine the old head into a clamp ring and use it to hold in an FAI motor insert, either a Rossi, Irvine or Cox Conquest one or better yet, one that's been made for the Nelson plug. I'm guessing a bit here, as I don't have either a TD15 or an FAI insert in my hands, so it might take a bit of thinking about.

The TD is a bit hard to gap, but based on FAI engines, shim the head for about 8-10 thou clearance from the squish band to the piston crown. If you want to run high nitro that gap can be higher, but if you want to stay with the 25%, that should make a fair starting point.

Dan's right about vibration, I hadn't thought of that.

When you run any engine, always start from a rich setting.

John
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RobinB
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« Reply #63 on: August 13, 2010, 03:26:59 AM »

Jeez, this thing has become a project in itself! As I already have enough projects to see me out I'll just put the word out and see if anything comes up. This motor didn't cost me anything anyway, and I don't have a model waiting for it.

If anybody hears of an available head, please let me know.

In the meantime, I have a pair of diesel-powered SLOP models to complete. After that my next engine 'sort-out' is to convert an OS Max15 III and an OS Max 19 which have R/C carbs. By that time we may know if pressure feed is going to be allowed in SLOP, which affects whether they go in SLOP or Classic models.

Plenty to do!
Robin
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« Reply #64 on: August 14, 2010, 08:55:26 AM »

Hi Robin

I extracted the following from my website. Jon Fletcher makes them and I recently bought one for my 15. They take a Nelson plug.
Contact details for Jon Fletcher Products will be found on www.pelaero.com.au
Cost from memory was AUD35.00 plus postage

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3. Nelson plug heads
Cox 049 & 15. Others to follow. (the 15 one is MUCH faster than the original Cox plug)

Ployd on OZ
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« Reply #65 on: August 14, 2010, 01:39:39 PM »

I put one of the Dodge-Nelson Glo bee heads on a C*x Conquest when this head and plug were first designed. I got a Nelson head from Henry and made a shrink fit band to match the slightly larger bore of the Conquest. It added 1000 rpm to the motor using the same prop and fuel on the same day. That was really dramatic!
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« Reply #66 on: August 15, 2010, 11:13:20 AM »

Peter, thanks for that lead - I'll contact Jon.

Robin
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« Reply #67 on: October 19, 2010, 04:30:01 AM »

Thanks again, Peter - the Cox now has a shiny new head (with Nelson plug) from Jon Fletcher.

Jon was very helpful, and his prices very reasonable.

Robin
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« Reply #68 on: December 28, 2010, 06:06:56 AM »

Some of the foregoing begs the question (to me at least) - what's available in terms of new engines?

Nearly all of the engines discussed so far are off eBay - nothing wrong with that, but is there anything suitable in current production (other than PAW)?

The last suitable engine that was generally available was the Norvel Big Mig .15, wasn't it?

The OS 10LA& LA15 are both good powerful engines and lighter than the FP range-you may have to buy a R/C version and convert. No current OS 20s are made. I have a K&B 20 Sportster on order from Mecoa for next season (it`s on their pricelist) which I will build a T34 or Graham Shacklocks 540 sq.in.SLOP for. I won our club 2010 SLOP event and State Open Power events with a OS FP10 Dixielander so power isn`t everything either. I have just machined a S/H K&B 20 Sportster down to 185gm.
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« Reply #69 on: January 06, 2011, 03:29:07 PM »

Hi Sandgroper,

Isn't T34 a Dave Hipperson 1/2A (TD 049) design?

........ if so, it might be a bit hairy with a K&B 20 (as well as a bit nose heavy) ........ (just kidding!)

John

p.s. The OS10 FP with a bit of nitro would be putting out about as much power as an AM35 (although on a smaller prop.) so it would be a decent combination in a Dixielander (in my opinion, anyway).
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« Reply #70 on: January 07, 2011, 03:38:50 AM »

John

The original T34 was a free plan in AMI and is SLOP/Small Open Power size, so a K&B 20 should be OK, but possibly a bit hairy. I recall Hippo writing that he was an AM 35 fan, but can't remember the precise motor he used in the T34.

A later issue of AMI did have a small 3 view of a 1/2A size T34. Both mags are in my 'pile', but could probably be found if anyone wants info.

Peter
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« Reply #71 on: February 03, 2011, 08:46:15 AM »

Sorry Glidermaster I was not very clear about the models-Dave also made a SLOP T34, a free plan was given away in A.M.Int or Aeromodeller years ago.We have a few built in West Aussie and they are very impressive with a good 15 or 20 up front.I have a new OS15LA converted from R/C and with a 7x4 APC on 15% and A3 short reach plug it pulled 18,700rpm after running in.

The short reach plug falls short of the combustion chamber by 1 1/2 threads or so,I put in a OS LC4 long reach plug and got 19,000 with 5%(ran out of 15%). The 15LA is the only OS I have found with this built in detuning and it may be to suit an R/C plug?

I also removed the exhaust stack,lightened the prop driver and machined the head down and it is now 123g-very very hard to beat a Fox 15 or TeeDee 15 for lightness.I also have a turbo plug head from a OS15 car engine which fits and will do some testing later.

I have just converted an OS10LA to diesel,it pulled 14,600 on 5% and a Taipan 7x4 black running in on glow.After conversion it weighs 109g and pulls the same RPM on the Taipan and 14,700-14,900 on an APC 7x4 with 20-25% castor oil fuel and runs very clean for a diesel and starts well.It sits in a 13oz-370g Dixielander.I have a couple of NIB OS20FP`s due soon and will convert one to diesel using a modified RJL 40 diesel head-$30 as against a Davies head which costs around $90 and more than the engine itself.

A diesel conversion for the OS15LA is also on the cards as in SLOP a diesel gets a 12 second run against 10 seconds for a glow.

Only Western Australia runs SLOP as a club and state contest in Australia with the eastern states running Aus Diesel as their restricted event.
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« Reply #72 on: February 03, 2011, 09:22:40 AM »

We also run SLOP as a 5x 3min max contest
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« Reply #73 on: December 11, 2011, 03:34:06 PM »

This is a K&B 20 Sportster which John, a clubmate of mine, has done some work on for me.
He didn't go as far as to slim down the prop driver, so it doesn't quite match Sandgropers version. It's 190 gm.
I was going to fit a K&B nva, but John said he'd like to fit something of his own and made the venturi and needle to fit where the original
radio carb had been. It's a 'Cox' type venturi, with 4 holes around the bore.
I don't have rpm figures for it yet, but John test-ran it and described as 'rather lively'  Smiley

Robin
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« Reply #74 on: December 12, 2011, 01:24:13 PM »

'Rather Lively'

Rather an understatement, I'd say! A good set of dihedral braces would be in order I think.
Got something in mind for this one, then Robin?
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