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Author Topic: CO2 Duration Anyone?  (Read 8661 times)
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PeeTee
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« Reply #25 on: April 04, 2010, 10:28:03 AM »

Pete

I overlooked your question regarding filling nozzles. I too have Modellas & Telcos and as far as I can ascertain the same CO2 bottle holder will do the both. All it needs to do is depress the ball in the female socket and seal reasonably well. I've used the same K&P sodastream nozzle (insert) for both.

Hope that helps

Peter
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« Reply #26 on: April 04, 2010, 04:16:56 PM »

Speaking of which Grin

Here's the Bottle, adapter and bags of spares (balls, mesh and various sized inserts from KP)

Some interesting stuff coming out about these things - thanks folks

I was also asked about the numbers I use on models so here is the highly technical way to make 'em... Roll Eyes

Draw or print your pattern then lay this atop several layers of tissue and back up with another sheet of paper; staple the whole lot together and cut out using a new blade (I like 10a) on a pad of newspaper. To fit either flood on using cellulose thinners or, as I did here, paint the surface of the tissue with thinned banana oil, position the letter and give another coat to seal.

Final shots are the finished wing and the pylon/nose area. The pylon will be cut into the fuz to give 65% CofG when I've added all the other bits.

Total weight so far is @25gms

Paul
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Re: CO2 Duration Anyone?
Re: CO2 Duration Anyone?
Re: CO2 Duration Anyone?
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algy
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« Reply #27 on: April 05, 2010, 12:21:45 AM »

Hi paul,

Good stuff. You have got the K&P charger plus spares. The one to go for. Just to give you some further information that might help that I found in notes that I had made.

Firstly the adapter inserts. The yellow one is 1.6mm in diameter. The Orange 1.9mm and the blue 2.00mm . The old Shark/Telco co2 motors can both be charged with the Blue nozzle insert and the Gasparian GM120 with the Orange nozzle insert.

Always loosen of the Knuled Steel Nut on the charger at the end of your flying session and release the pressure by inserting an old filler nozzle or similar This ensures that the cylinder/adapter seal does not swell if left under pressure for a long period. If it does swell leave it in a pressure released condition for as long as possible prior to removal to allow the seal to return to size. How do I know all this is good manufacturer advise?  Cos it happened to me!

Here is my little tip if the plastic nozzle insert cannot be removed when trying to change. Put the end nozzle assembly in a small amount of water and lots of ice cubes in a glass then put it all in the fridge. The plastic insert will shrink and it can then be easily poked out with a bamboo skewer. Use bamboo or similar so as not to damage any threads or the nozzle.

Hope those little bits help.

Cheers
Algy

PS: I am off to order some spares from K&P. One never knows.
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« Reply #28 on: April 05, 2010, 11:53:44 AM »

You fellows build and write messages so fast that I just can't keep up. Forgive me then if I refer back to replies #20 and #22 which you have probably forgotten about by now. They talked about the great amount of upthrust on Steve Philpott's and Gerd Wobbeking's models. Am I being obvious when I say that Upthrust or Downthrust is a matter of how much the thrust line passes below or above the CG. On a typical CO2 model, with the motor mounted on a pylon above the nose, the thrust line is almost certain to pass several inches above the CG giving massive Downthrust. Even if the thrustline with respect to, say, the pylon is inclined upwards there is still almost certain to be a great deal of Downthrust.

Incidentally, although there may be practical reasons for putting the motor in such a position I would have thought the large moments created, which must be balanced by other moments, would not give the most efficient aeroplane.

John
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« Reply #29 on: April 05, 2010, 03:08:29 PM »

Thanks John

I wondered why very few other models used such a distinctive thrustline arrangement - that answers an unanswered (and unasked) question.

Suprisingly I noticed that Dave Hipperson's otherwise conventionally arranged model also required upthrust. The only slightly unusual aspect of the design being a flat bottomed wing section Undecided I'll see if I can find the drawing.

Thanks for the additional information Algy - I'll keep an eye on the seal.

Now starting to slow down, coz without a motor there's a limit to how much more I can do.

Paul
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algy
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« Reply #30 on: April 05, 2010, 09:24:45 PM »

Hi John,

On the Upthrust/Downthrust issue with CO2 powered duration type models I have only built one. It was from a free Aeromodeller plan published in the 1970s. Still have the model but cannot recall the name of the plan. Think it was an Ian Dowsett? design. (Swift) ?? It flys very well powered by a Shark CO2 engine and needs the D/T to get it down. But only with upthrust!!

It is a normal pylon layout with the motor mounted in the normal position on the front of the fuselage. Not up on the pylon with or above the wing . It has a flat bottomed wing section as well. But it also requires upthrust to fly properly. Could never work out why. But there you are. One of life's little aerodynamic mysteries.

Cheers

Algy
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« Reply #31 on: April 06, 2010, 02:50:15 AM »

Upthrust, downthrust I know not the answer, but the motor on a stick/upthrust designs must have something going for them as Steve Philpott has won the British FF Nats CO2 event no less than 12 times, and Gerd Wobbeking, twice. That's good enough for me............... now where's that bit of carbon tube? Cheesy

Peter
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« Reply #32 on: April 06, 2010, 09:25:02 AM »

As a variation on the method to cut out numbers I offer the following. Get a piece of glass scrap, mine is about 12" x 12", and lay up several layers of tissue using thin dope. I use nitrate dope. Make a paper pattern of the numbers using a ink jet printer (that way the ink will not run) and dope that on the top of the tissue layers. Take a new knife blade, I use Excel #11, and cut out the numbers. Remove most of the bigger chunks of paper but do not try to remove intricate details. Flood the glass with thinner and keep it wet for awhile and the multi layer construct should release from the glass. Now drop the multi layer construct into a dish of thinner and all of the layers will release and fall apart. I have used up to 5 layers of tissue with this method. I use the one set of numbers and store the remainder in an envelope for the next model.
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« Reply #33 on: April 09, 2010, 06:02:22 PM »

Well you did it guys. Went and picked up a paintball tank to go with an adapter I've had laying around. Rather than the high tech duration stuff you're doing I'll build a little 21" Wedgy for my GM63 to start.

Ignorant question ... do GMOT and Telco use different filler nozzles? I picked up a Telco from a friend and another friend is giving me another. But with the small 8gm cartridge filler from GMOT I only get maybe 10 seconds of motor run at best. I wonder if maybe the tank isn't getting filled. Adjusting the head clearance didn't help either.

bill
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« Reply #34 on: April 10, 2010, 02:24:52 AM »

Bill

As far as I know, you can fill both the Telco & Gasparin tanks using the same filler adapter. I'm talking about the K&P one for a Sodastream bottle, and I can't recall changing the insert for a Telco. Are you holding the charging bottle inverted so that you get a liquid charge, as this'll give a longer run.

As for adjusting the Telco, you realise of course that the adjustment isn't made by screwing the head up or down. The adjuster is an eccentric crankshaft bearing & you'll see the metal adjustment flange just behind the prop driver. Telcos came with a little metal adjustment spanner, but I suspect that needle nose pliers work just as well. I apologise if you knew all of this anyway Embarrassed

Peter
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« Reply #35 on: April 10, 2010, 09:59:13 AM »

Thanks Peter. Glad to hear I don't need two different adapters. I did know about the Telco adjustment but only because I bought a book by Tony Peters on CO2 a few years back. I'm too lazy to use DT's with most of my other stuff but this CO2 will definitely be the exception. Getting pricey as someone mentioned a few posts back. Don't ever apologize when sending answers my way, assume ignorance and you'll be mostly right. Roll Eyes

bill
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« Reply #36 on: April 19, 2010, 09:29:20 AM »

Yippee, Father Christmas came a bit late this year Grin

I collected my CO2 motors yesterday and what a goody bag (or possibly that should be vanity case) Wink

In addition to 4 Telco's and a Modela there is a lovely little Gasparin GM24 which is far too nice to risk in a duration model... maybe destined for a peanut for indoors Undecided

There are also loads of Telco chargers and spares box with 'O' rings pistons and various important looking little dodads so I'm well chuffed.

The Modela will be sold and possibly a Telco too...

I'm going to use one of the Telco's in my CO2 Model and will play about to see which one I like the best.

Cheers for now

Paul
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« Reply #37 on: April 19, 2010, 10:19:42 AM »

Paul,
vYou are indeed a lucky fella! I took a few hours and built a fuselage for a set of wings & tail I had around. Original intent was to fit one of the Telcos I also received as gifts. But both are pretty rough right now. Need a bit of reading to get them running well. (would anyone have a Telco parts diagram and/or manual they could scan??) So I'll go with my GM63 for starters.

Thinking of building another Tom Thumb for CO2. Think a GM120 would be too much motor?

bill
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« Reply #38 on: April 19, 2010, 10:52:39 AM »

Paul

A goodie bag indeed. May I suggest that you test run each of the Telcos to see which performs best (rpm & motor run time). the Modellas are lusty runners, but you can't use that tank as it's 5 or 6cc at least - the 3 cc ones are about half the height (and Flitehook used to have some in stock). The G24s are lovely motors but as you say, too good to lose in a duration model!

Does this mean that you'll be flying CO2 at the London Gala next Saturday? If so I'd better get trimming my model Grin

TTFN

Peter
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« Reply #39 on: April 19, 2010, 12:30:36 PM »

I suspect that the Gasparin G63 is a better bet Bill, it's just that I don't want to lose one! (Actually that presupposes that I get one beforehand, but you know what I mean. Oddly enough losing a rubber model is one of those things that you get used to... losing a motor however)Undecided

Blimey Peter - bench running... testing... ain't that what the rounds are for? Wink

I doubt I'll get much time this week to finish the model; maybe the Nats?

So the standard tank on the Telco's is too big eh? I did wonder... best have a chat with Pauline and flutter my eyelashes at her (Can you do that over the phone I wonder) Kiss

I expect to be shown how these things are supposed to fly - No pressure though Peter.

Your fans await...

Paul Cheesy
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« Reply #40 on: April 19, 2010, 03:41:19 PM »

Paul,

It is the Modela that has too large a tank.

Telco std tanks are fine (I think).

John

p.s. Pete's right, bench test 'em beforehand.
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« Reply #41 on: April 19, 2010, 03:59:42 PM »

Cheers John Smiley

I'll run 'em up sometime this week...

Paul
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« Reply #42 on: April 19, 2010, 06:21:50 PM »

John beat me to it Grin

Although I often work on the trim as you go basis, if you have a knackered (good technical term that Cheesy) motor, that's the flight gone for a chop, and changing them in the field should be done as a last resort. It would help if you could beg, borrow or steal a rev counter (I assume being a glideriste that you don't have one). Another snippet, for what it's worth, is that the standard Telco prop is too small for our purposes. I use a Modella prop on my Tornado 69 (which is of a similar capacity) and a GWS 7x6 is worth trying, but in both cases a test flight is beneficial to ensure that the model climbs away. Flying in ground effect for 2 minutes is not good for the nerves!

As for feeling pressure, I'm happy that I got lucky last year Roll Eyes, and will work on the basis of the moving hand, having writ, moves on (well that's my excuse anyway!).

Nighty night

Peter
ps I owe you an answer on oil - I've not forgotten
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« Reply #43 on: April 19, 2010, 10:47:26 PM »

Hi Bill,

I have the Telco Parts/Instruction information sheet you are after and have scanned it into a PDF file. Send me you email address and I will get it to you. It is for the Telco Turbotank model but it is exactly the same motor. I still have two of these turbo tank models and they go very well.

The first lot of original Telco moters released in the mid 70s are the ones to get. I bought one and it is still going strong. Their manufacture was then taken over by another company and the subsequent engines never lasted as long. I know cos I bought a few. They used different metals in the crankshaft bearing which wore rather quickly. But I have many spares and am able to soldier on. These small CO2 engines can be a bit cantankerous/challenging/frustrating but I find it all part of the fun. Some were very good with no problems. Some were not so good.

Incidentally to all who have the English Telco or Humbrol/Shark I have just recently found a very good supplier for the 1/2 inch 10BA steel propeller retaining bolts.  It is "BA Bolts Engineering in the UK". They gave me brilliant service at a low cost. I bought 50 0f them so they should last a while. To contact them email: [email protected] or goggle on the net. These steel bolts can prove elusive to locate. Brass 10ba bolts are easy to find but they bend to quickly.

I have already posted the name and contact details of the supplier/manufacture for any one looking for spares for the KP sodastream CO2 adapter. I ordered two sets and Icelandic Volcanoes permitting , they should be in the post box any day now.

Cheers

Algy
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« Reply #44 on: April 19, 2010, 11:29:46 PM »

Thanks a ton Algy, sent you a PM.

bill
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« Reply #45 on: April 20, 2010, 06:02:45 AM »

Algy,

The Telco that I have, I picked up on a temp. duty assignment to Greenham Common around 1975-6, so hopefully it's one of the "good" ones. I've run it a few times, but still gets stored in it's original (somewhat tattered) truncated triangular box. The instructions have gone AWOL over the years, so I would also like a copy also.

My MODELA is going into a Citabria, but I might try an enduro model for the Telco.

Pete
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« Reply #46 on: April 20, 2010, 06:32:17 AM »

Okay just been playing with the motors... I see what you mean Algy Tongue

You will have noticed that none have the long coil of tubing which is good in some ways but makes the soldered joints a little vulnerable if you run 'em holding them in your hands.

The Modela needed a few squirts of oil to free it up and then hammered away quite happily Cheesy

Of the Telco's none have been run since the late 80's apparently and I suspect that seals etc. will need changing. All did run though, as is, which was encouraging. I used a Telco prop since one was in the box to get a setting that they seemed happy on and then switched to a GWS 7x6 (same as I use in the E30) which was full size and it was clear even doing these rudimentary checks that one motor seems better than the others.

The only slight problem is the Ali nut behind the prop used to set the motor speed unwinds in use Sad
Any suggestions?

I was using the sparklet bulbs in one of the little hand chargers and when I held the nut (to stop it unwinding) I was getting 50-60 seconds which seems reasonable...

Paul
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« Reply #47 on: April 20, 2010, 08:57:59 AM »

Hi,

Pete send me your email address and I will send you the Telco instructions PDF file. I am not the worlds expert on these engines but it sounds like you might have one of the original manufactured Telco CO2 motors. Mine also came in a triangular box. The other clue is the the speed control nut behind the propeller. They were originally round with a serrated edge. Later models swapped to an hexagonal shaped speed control nut. There were also a few changes to the cylinder head fins to along the way but I lost track of those.

Paul glad to hear they are at least running. I had a look at the photos you posted. Yep you have been short changed with the copper feed pipes. Who ever shortened then was a very very silly person.

One they will be hard to install in a model and second as you pointed out it will make it very likely that the pipe will fracture from movement. They are originally supplied with a longer feed pipe to enable a small coil to be made above the engine to stop this happening. I do not know where you can buy this copper pipe. It has a very small diameter. All is not lost though. You you should be able to get some aluminium or similar tubing from your hobby shop of the same outside diameter of the copper feed pipe and Araldite in a section. This will work. It will take the pressure I have done it. To loosen the Arildited joint if you have to later, press a hot soldering iron on the joint. It will make the Araldite crumble. The pipe will become loose. This also works. I have done it.

You will have to find a supplier of "O" rings to renew those if you have to. Auto shops can be a big help. Take the old ones to match them up. Mine seem to last a very long time. You have already found out that these engines love being oiled so keep that up.

I have never had the problem of the speed control nut moving after being set. They are a push interference fit into the crankcase. They actually work by moving the crank shaft up and down and so raise the piston up and down to alter the speed.

All I can suggest is unscrew the propellor retaining bolt. Take of the propeller and try and gently pull it out. You will probably have to take the piston out also. To do that pop out the small rear white cap on the back of the crankcase. Then when you get it out clean every bit of oil from it and try a few coats of paint. This might increase it's diameter and make it make it grip tighter in the crankcase. I have not done this but it is something I would try. Just a word of advise when working on these little beasts. Do it all over a tray and work slowly and carefully and do not use force on anything.

60 sec is quite a good run so all is ok there. You should be able to get it a bit longer by adjusting the speed control nut.

Cheers

Algy
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« Reply #48 on: April 20, 2010, 09:15:36 AM »

You're right about the speed control. Mine is the round 'un. PM on the way, but you should be able to access my addy thru my profile or the letter icon below my screen name in the message.
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« Reply #49 on: April 20, 2010, 09:18:16 AM »

Thanks Algy that's very helpful

Fortunately I've got several packets of spares which includes O rings and the balls from the top of the cylinder so I should be okay for a while there.

I'll try the paint idea - sounds like a good plan. Failing that I'll try swapping it for one of the spares to see if I can get a better fit.

The reason the pipes got shortened originally I suspect was the engines were used in indoor duration models and knowing the records being broken I can see why an extra 3" of pipe was deemed surplus weight. Incidentally I've got a number of the props used in these attempts; large diameter single bladed folders Shocked
I'll post some pics when I get a chance

Cheers
Paul
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