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OS GT33 33cc gasser

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Old 10-05-2012, 11:44 AM
  #351
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Default RE: OS GT33 33cc gasser

Thanks MTK. I did just that. They said it is the TT-0522-A. Got one coming. Your right on about the 1.60. I already had the spacer for the backplate. Just finished the installation today in a Black Magic Pattern Plane. Need to balance her out and fly. Thanks much for your reply.
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Old 10-05-2012, 12:15 PM
  #352
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ORIGINAL: dobro

Thanks MTK. I did just that. They said it is the TT-0522-A. Got one coming. Your right on about the 1.60. I already had the spacer for the backplate. Just finished the installation today in a Black Magic Pattern Plane. Need to balance her out and fly. Thanks much for your reply.
Oh cool....Did you install a soft mount? Pipe?

The OS33 GT, piped, is an OS160 FX on steroids. Hold on to your socks; you're gonna love the authority the engine will fly the BM with. Go straight to a 19x10 prop for break in. Don't use anything smaller since it will give you a false indication of the power.

I'm using a 20x10.5 PN now, but have used several different props in this size and they all work great. Tremendous top end which is completely unecessary for an 11 pound pattern plane. I fly at half throttle, maybe 6K rpm but probably lower. I've got some info in the Pattern pages
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Old 10-08-2012, 08:36 AM
  #353
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Default RE: OS GT33 33cc gasser

Hi MTK, Yes I'm using a carbon fiber pipe. I was able to modify the header from my 1.60 to fit the 33. I'm experimenting with the engine mount. If it doesn't work well, I'll make a soft mount like some of you have already done. I used 3/4" stand offs with a 3/4"soft lined bushing. Basically what I did was make 4 aluminum bushings the same size as the dubro anti vibration mount. I used the rubber inserts from the dubro mount in the bushings. To help keep the motor mount bolts from backing off, I backed them up on he backside of the firewall with a 5mm lock nut. Man the only bad thing about these pattern planes is not being able to have full access at the engine. Kind of like building a ship in a bottle so to speak. If I have to make a soft mount, the carb will have to be inside of it for the engine length to work. Ever seen this setup done before? What kind of prop are you using? I have all apc but I see references to using wood to prevent bent shafts with a prop strike. Thanks Bob.
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Old 10-08-2012, 08:57 AM
  #354
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Default RE: OS GT33 33cc gasser

Bob,

If I understand your soft mounting right, you will use 4 Lord type rubber isolators, one for each stand off. That's worth a try. Don't know how long it would hold together. BTW- the Lord mounts (Mc Master Carr ) can be purchased with studs on both ends. You first would screw the Lord onto the firewall and then screw the stand off onto the Lord mount

Take a peek at the pattern forum on my OS33 for Pattern thread. I have photos that show some of the carb inside the rubber isolator. I don't like putting the needles inside. I keep the carb out far enough to have access to the needles
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Old 10-08-2012, 09:21 AM
  #355
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Default RE: OS GT33 33cc gasser

Thanks, I'll check out those lord mounts. If I get a chance later I'll take a pic and post it. This is definitely a learning curve for me on soft mounts.
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Old 10-15-2012, 07:54 AM
  #356
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Default RE: OS GT33 33cc gasser

Hey there MTK, Finally had a chance for a pic. This is the mount set up I'm going to test . I have the bolts backed up with a lock nut after the blind nut on the backside of the firewall. If there's too much vibration I'll back track and make a soft mount .
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Old 10-15-2012, 07:57 AM
  #357
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Default RE: OS GT33 33cc gasser

Ok sometimes things just don't go right the first time. Here's the pic to the above post
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Old 10-15-2012, 08:13 AM
  #358
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Default RE: OS GT33 33cc gasser


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ORIGINAL: dobro

Ok sometimes things just don't go right the first time. Here's the pic to the above post
Bob,

It looks like the Dubro grommet set-up as spacer on your stand offs. Be careful with that one, it doesn't actually isolate much. Plus, a bolt running through the whole thing couples the engine to the firewall directly.

I'll try to post a photo tonight of what I thought you were trying to do....
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Old 10-15-2012, 08:28 AM
  #359
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Default RE: OS GT33 33cc gasser


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ORIGINAL: theKM

I gotta say, I'm loving my GT33 so far... it does start backwards every now and then, just kill it and flick it again, I can't say I've ever had a problem starting it by hand... just a few flips and it's purring like a kitten. Simply a wonderful engine so far. On my 74'' 3DHS Edge (10.5lbs), it hauls the mail. I had a 20x10 falcon on it and it's great, smooth and quiet... but I'm propping down now for break-in, I may return to the Falcon.

Here's a video of it flying on the 20x10 without any real effort to tune it properly at this point (just set the high for a little richer than peak RPM and went flying)...

https://vimeo.com/39382446
Really with the GT33 10.5 pounds, is that weighted with a scale? I just weighed my DLE30 3DHS slick with the lighter DLE and it was over 11 pounds on my digital scale, and I have nothing added to it all stock except a JTEC inverted Pitts that is like 2 ounces heavier.
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Old 11-09-2012, 12:52 PM
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Default RE: OS GT33 33cc gasser

I'm in the process of installing an OS GT33 and am wondering about fuel consumption. I've been known to use as large of a tank as I can get into the airplane. That needs to change to cut down on excess weight. Can anyone give me an idea on a 16 or 20 oz tank considering most of the flight will be around 3/4 throttle, I'm guessing.

Thanks,
Richard
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Old 11-09-2012, 01:11 PM
  #361
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Default RE: OS GT33 33cc gasser

I use a 16oz tank. I get 20 mins with at least a 1/3 to spare.
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Old 11-09-2012, 02:04 PM
  #362
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Default RE: OS GT33 33cc gasser


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ORIGINAL: RHarding

Can anyone give me an idea on a 16 or 20 oz tank considering most of the flight will be around 3/4 throttle, I'm guessing.

Thanks,
Richard
I had to reduce my tank from 500 ml (about 17 ozs) down to 340 ml (about 12ozs). The 500ml tank was giving my flying buds fits since I'd hog the sky for 25 minutes every flight.

I run my engine at 2/3rds throttle most of the flight so a 12 oz tank made for a more neighborly 15 mins...YMMV
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Old 11-09-2012, 05:15 PM
  #363
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Default RE: OS GT33 33cc gasser

Thanks guys. I guess 16 oz is it. Anything else about the GT33 I should know.

Thanks,
Richard
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Old 11-09-2012, 05:45 PM
  #364
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Default RE: OS GT33 33cc gasser


Quote:
ORIGINAL: RHarding

Thanks guys. I guess 16 oz is it. Anything else about the GT33 I should know.

Thanks,
Richard
The only thing i noticed was if you run the engine leanat all, even just breifly the exhaust will come loose, even when using nord lock washers. I'm running the stock exhaust, it may be a different story with a pipe and manifold.

I have to say i'm really impressed with this engine, it's had around 8 litres through it turning a G=sonic 18x12 @ 7800rpm (2 blade)
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Old 11-10-2012, 06:20 AM
  #365
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Default RE: OS GT33 33cc gasser


Quote:
ORIGINAL: RHarding

Thanks guys. I guess 16 oz is it. Anything else about the GT33 I should know.

Thanks,
Richard
Yeah there area couplethings that can be a little tricky at first. Starting the first of the day without a starter is a little finicky. After you choke it and get it wet, open throttle a few clicks and give the prop a strong,fast flip. The CDI has to sense the prop moving through at about 150 rpm equivalent.

A starter makes this simple enough. I use a Dynatron. You don't have to have but it just makes for simple starts

If the engine all of a sudden won't start or it runs super lean, suspect the rear cover. After only 4 runs mine did that early on and it just gave me fits. Had to send it back to Hobby services where they found a cracked rear cover. Musta been a factory defect because the replacent cover has been working great.

The engine is a stump puller;turns surprisingly big props. My set-up is at least the equal of a YS175 4stroke, on 25% nitro....YMMV

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Old 11-10-2012, 07:03 AM
  #366
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Default RE: OS GT33 33cc gasser

Matt, I have found another neat header/mufferly that may be worth a look for folks on a budget. Here is the link. The low $80ties price make it worth a look. The header looks very adaptable to this engine.http://www.horizonhobby.com/products/silencer-system-complete-35gt-2-40gx-EVO30984268E-http://s7d5.scene7.com/is/image/horizonhobby/EVO30984268E_a0?$pdpLand$-I found this item on eBay. The muffler itself is around 8oz-Bob (Sorry for the dashes, but I can't seem to upload returns.)
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Old 11-10-2012, 11:16 AM
  #367
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Default RE: OS GT33 33cc gasser


Quote:
ORIGINAL: MTK

If the engine all of a sudden won't start or it runs super lean, suspect the rear cover.

Matt, after reading this you got me thinking. Two weeks ago when i last used the 33 the enging stopped in flight, i dont get dead sticks, i hope i dont sound arrogant but it just doesnt happen i'm far too carefull with my stuff.

When i took the canopy off and held the aeroplane vertically up and there was only a tiny amount of fuel in the tank (maybe about 3=4 mm) so i put it down to running out of fuel and thought nothing more of it, untill i read what happened to you. I use a felt clunk in the tank so it should really have used every last drop of fuel.

Thia afternoon i filled the tank up and tried to start it......and yip.....i could not get it started. This engine was running really sweet before so i dont want to play around with the needles at this point. I'll pull the engine out later and check the rear cover before i do anything.

Cheers for the heads up
john
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Old 11-11-2012, 01:13 PM
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Default RE: OS GT33 33cc gasser

Managed to take the engine out this evening and i found the plywood bottom coming apart on the engine box, but the rear cover/backplate were fine.




The engine looked like it had never been run


I repaired the enging box, bolted the engine back on and tried to start it.....again it wouldnt start so i opened up the low end needle by exactly 1/8 of a turn and this time it started as normal.

I would expect the engine to 'richen up' as it runs in and not go lean as abruptly as it did ?
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Old 11-14-2012, 06:46 PM
  #369
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Default RE: OS GT33 33cc gasser

I am thinking about replacing a worn out Zenoah G-38 that is on a 71" Ziroli P-47. On the G-38 I has a toggle switch on the fuse that is connected to the engine to ground it out for a kill switch. What type of Kill Switch would be best for the OS GT33 Gasser?
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Old 11-15-2012, 08:28 AM
  #370
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Default RE: OS GT33 33cc gasser


Quote:
ORIGINAL: ekir

I am thinking about replacing a worn out Zenoah G-38 that is on a 71" Ziroli P-47. On the G-38 I has a toggle switch on the fuse that is connected to the engine to ground it out for a kill switch. What type of Kill Switch would be best for the OS GT33 Gasser?
I used the powerbox switch that lets me kill it from the transmitter. i'm sure there are others.
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Old 11-15-2012, 08:49 AM
  #371
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Default RE: OS GT33 33cc gasser

On my gas engines I use an Mpi heavy duty switch with a charge port. Mount it between the ignition battery and the ignition module. It works good plus it's easy to plug in for charging. You can get these from Maxx Products. www.maxxprod.com

Richard
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Old 11-15-2012, 10:36 AM
  #372
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Quote:
ORIGINAL: RHarding

On my gas engines I use an Mpi heavy duty switch with a charge port. Mount it between the ignition battery and the ignition module. It works good plus it's easy to plug in for charging. You can get these from Maxx Products. www.maxxprod.com

Richard
Richard,

You may not know about the Tech Aero Ignition Battery Eliminator or IBEC. You could look it up on Tech Aero's website.

It's a device that serves as switch connecting between the CDI and into a spare channel such as retracts on your RX. You can then switch the CDI On and OFF by flipping the retract switch on your TX.

CDIgets its juice from the regular radio battery which you charge before flying anyway. No second battery charging required.

Since it's a remote switch thatyou actuate from your TX, it is safer.....no more reaching behind a prop to turn ignition off. Plus, because it is connected to your radio, you can set-it up to a fail safe position in the event your signal fails for some reason. Shutting off the CDI in the event of signal loss, is a good move....no fly aways. You still crash but it's findable

If you are using a 20 year oldor newer radio in 72 MHz of 2.4 GHz, the IBEC is an excellent filter for RFI noise. It's all built in. There will be no radio interference as some might claim. I use the device in all of my gas airplanes. And BTW, you will save around 4-5 ounces of extra battery weight and switch
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Old 11-16-2012, 08:45 AM
  #373
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Default RE: OS GT33 33cc gasser

Thanks for the info. Sounds good. I will definitely check it out. I like saving weight. Question, if one battery powers receiver and engine, what mah battery do you use? If I'm using 7 high output digital servos on a 6 volt 2500 mah and the same for the engine what would you recommend? I'm thinking maybe a 4000 mah 6 volt sub c as a minimum.

Again, thanks for the info.

Richard
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Old 11-16-2012, 09:08 AM
  #374
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Default RE: OS GT33 33cc gasser


Quote:
ORIGINAL: RHarding

Thanks for the info. Sounds good. I will definitely check it out. I like saving weight. Question, if one battery powers receiver and engine, what mah battery do you use? If I'm using 7 high output digital servos on a 6 volt 2500 mah and the same for the engine what would you recommend? I'm thinking maybe a 4000 mah 6 volt sub c as a minimum.

Again, thanks for the info.

Richard
My pleasure, glad to help. My models are 30-60cc gas models and practically all use2 digital high speed and torque servosdriving ailerons, 2 moderate torque, high speed digital servosdriving elevators, 1 heavy duty/high torqueand speed digital servo driving rudder 1 std servo driving throttle and occasionally 1 std servo driving choke.

My battery driving both CDI and radio is 1800 LiPo regulated to 6.4 V or a 2200 Li-Ion regulated the same. The IBEC takes the 6.4 V and regulates further to 5.5 V to drive the CDI with. The IBEC has 3 voltage selections available by using a jumper, from 5.0 to 5.9 V if I recall. You may want to contact Tech Aero directly and askthem to set it for you in the middle.

I get 75 minutes of flying time on my set-ups; that's 5 15 minute flights. I check the LiPo voltage and make certain I don't fall below 7.4 volts (fully charged voltage is 8.4V). Your 2500 should get you similar flight times. 4000 would be way overkill unless you fly 2 hours of actual flight time per session.

All of my engines are soft mounted so vibration level is lower in my set-ups and the servos don't have to fight as hard to maintain position. My battery usage therefore is very predictable at just about 250 ma per 15 min flight. Yours may be a little higher at maybe 300 ma per flight assuming your engine is hard mounted

Good luck
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Old 12-06-2012, 06:27 PM
  #375
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Default RE: OS GT33 33cc gasser

Those interested in quieting the 33 or any smaller gassie up to a 60cc give or take, here's a Utube link to a model I designed and built. The engine is the OS33 GT, on my soft, rubber isolation mount, ESComposites 40G tuned pipe and apc 20x10.5 prop. Quiet enough to where background noise drowns me out in places

I did not discuss the Tech Aero IBEC used in the model. But I've discussed this unit's benefits before. Have it set-up on the retract switch, a very convenient spot on my TX. The convenience and safety is worth a lot.... Check the Tech Aero site for details

Enjoy! http://www.youtube.com/watch?v=iAd8d...ature=youtu.be
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