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OS GT33 33cc gasser

Old 12-01-2011, 10:42 AM
  #176  
racerman27410
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Default RE: OS GT33 33cc gasser


ORIGINAL: selnekav

Hi,
Do you see any difference in terms of vibration level between the DLE 30 and GT33 ?

Thanks

yes the OS engine is much smoother in operation.
Old 12-01-2011, 06:01 PM
  #177  
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Default RE: OS GT33 33cc gasser


ORIGINAL: racerman27410

My OS Gt33 runs fantastic....

it has ldled and carburated perfectly from the first tank of fuel. You just have to remember to crack the throttle open a bit on startup or it may run backwards.

the muffler does great at actually doing what a muffler is supposed to do..... its' at least as quiet as my DLE with cannister exhaust.


i have not flown mine yet as i'm waiting for my 44.5mm standoffs to arrive so i can put the cowl on (the 5x44.5 standoffs will let the GT33 perfectly replace a DLE30 V2... same footprint, same length)

from ground testing the GT33 is going to be THE engine for 3D.... it feels directly connected to the throttle stick just like an electric motor. The throttle response is THAT good. My engine runs just as good as the engine Joe is flying in that video.

the engine also had a lot of compression even before the first run.... my DLE could easily be turned over by hand (and still can be) this OS engine just pops! using the exact same prop as i was using on my DLE (20/6 Xoar) i can tell the engine has way more power than the DLE... which is amazing to me considering the lightening fast throttle response.

price is right in line with a DLE too... i got mine for 369 from tower w/ free shipping (super saver 50 bucks off coupon) but i had to buy the OS standoffs so that added another 31 bucks.... still for the way this thing is running i am completely happy with my purchase considering the quality of the piece, the nice muffler that actually works and the proprietary ignition that will let you run up to 7.4 lipos without the need for a regulator.

I think OS nailed it on this one.

I'll be sure and post a report once i actually get to fly it.

Fellas, you can get stand offs from Mc Master Carr. I use the 3/8" hex aluminum but the 5/16" work just as well and at lower weight. The 3/8" hex comes threaded with anything from 4-40 to 1/4-20. Lengths are standard so if need custom, you will have to cut them yourself. These are much less expensive than anything stock from the engine makers
Old 12-01-2011, 06:08 PM
  #178  
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Default RE: OS GT33 33cc gasser



BTW- spoke with a guy at Hobby Services. Guy didn't know anything about where my engine repairs stood. Took 10 minutes of waiting on the phone to find out anything. At first it was "They haven't got to your engine yet" Then after I pressed a little, "oh they started working on it".

Finally, it was "we'll have an answer for you in a few days".

I am not feeling the love from these people. I have a bad feeling that this one will be chalked up to a bad experience
Old 12-01-2011, 06:18 PM
  #179  
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Default RE: OS GT33 33cc gasser

Yep, Hobby Services sucks.  The last time I had an engine start in reverse was a 72 Yamaha.  This is 2011, there is no excuse for that and it is very dangerous.
Old 12-01-2011, 06:49 PM
  #180  
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Default RE: OS GT33 33cc gasser

Wow,

Hobby services must have changed in the past few years. Never had a problem with them nor has my friend. As far as starting backwards, it doesn't happen if you simply open the throttle a little. Want dangerous, try peaking the needles on a YS and watch the double nutted prop and spinner pop off. That's dangerous!
Old 12-01-2011, 07:39 PM
  #181  
racerman27410
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Default RE: OS GT33 33cc gasser


ORIGINAL: ghoffman

Yep, Hobby Services sucks. The last time I had an engine start in reverse was a 72 Yamaha. This is 2011, there is no excuse for that and it is very dangerous.

not dangerous IMO.... if you open the throttle it will cut off..... then restart with the throttle cracked open a bit no worries.

Old 12-02-2011, 07:50 AM
  #182  
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Default RE: OS GT33 33cc gasser


ORIGINAL: racerman27410


ORIGINAL: ghoffman

Yep, Hobby Services sucks. The last time I had an engine start in reverse was a 72 Yamaha. This is 2011, there is no excuse for that and it is very dangerous.

not dangerous IMO.... if you open the throttle it will cut off..... then restart with the throttle cracked open a bit no worries.

The few early times mine was started (and actually ran well), the throttle was about 1/8 open. Flipping pretty hard still resulted in backwards starts. The engine was the first one I have owned that did that (I've owned 10 gas engines in the past 15 years and currently have 5 that I use regularly) None of my other engines ever started backwards. Very strange to me!

I tend to agree...not really a dangerous situation. Simply stopped and flipped again until it started right.
Old 12-02-2011, 09:33 AM
  #183  
Antique
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Default RE: OS GT33 33cc gasser

Something wrong with an ignition on a gasser that will let it run very well backwards...
Old 12-06-2011, 09:23 AM
  #184  
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Default RE: OS GT33 33cc gasser


ORIGINAL: MTK



BTW- spoke with a guy at Hobby Services. Guy didn't know anything about where my engine repairs stood. Took 10 minutes of waiting on the phone to find out anything. At first it was ''They haven't got to your engine yet'' Then after I pressed a little, ''oh they started working on it''.

Finally, it was ''we'll have an answer for you in a few days''.

I am not feeling the love from these people. I have a bad feeling that this one will be chalked up to a bad experience
Spoke to them again today. The latest is that a mounting lug was broken during shipping so the backplate needs to come from Japan. Been over 3 weeks and it looks like another 4-6 before I see the engine.

They said that they ran it twice and it ran fine. Why don't I believe that ?

Very disappointed in this whole ordeal
Old 12-06-2011, 10:46 AM
  #185  
texasclouds
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Default RE: OS GT33 33cc gasser

That kind of 'customer service' is typical these days. :-(
Old 12-09-2011, 04:20 PM
  #186  
hobby_man
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Default RE: OS GT33 33cc gasser

so guys thumbs up or down on the gt33???? can you hand start the gt33 or do you have to use a starter?

do I buy a gt33 or the syssa?
Old 12-09-2011, 05:49 PM
  #187  
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Default RE: OS GT33 33cc gasser

You should be able to hand start either one?
Old 12-09-2011, 08:11 PM
  #188  
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Default RE: OS GT33 33cc gasser


ORIGINAL: hobby_man

so guys thumbs up or down on the gt33???? can you hand start the gt33 or do you have to use a starter?

do I buy a gt33 or the syssa?
The SAP 180HP is great little engine that is simple to set-up, start and feed. Excepting for a few very early starter starts while I was getting familiar with it, I have always hand started them ( I have a couple). Very straight forward stuff. Very good power especially when piped; just a forewarning, this engine is a revver so suggest that you prop it to run at 8500 rpm min and it will be happy

The OS has been an absolute bear to start and feed. However, the power is tremendous in this size gas engine, except the blasted thing just won't start. Unfortunately I got a taste of its power in the first couple runs when I actually got good starts out of it and I am definitely interested but not when it's unreliable as it has been. The other unseen problem is apparent lack of tech support (my perception is lack of knowledge) from Hobby services. I'd hazard a guess and say I won't be seeing mine for at least another month from the repairs HS is doing, and it's been over 3 weeks (Nov 18) since I sent it in. Don't ask them what the repairs were, they don't know....very frustrating

So the answer I'd give you is to go with the SAP for reliability alone

Another choice is the Mintor 38...Excellent handling, simple starting and feeding, terrific throttle response but only fair power. However this one tends to turn much larger props than the SAP at lower rpm. Your decision should depend on how you want to use the engine. If you want to race it, get the SAP. If you want scale like speeds, get the Mintor. If you want both, get the OS but be prepared to suffer with that one
Old 12-14-2011, 03:19 PM
  #189  
Capt G
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Default RE: OS GT33 33cc gasser

First runs today on the OS GT-33. Very easy to start but first starts ran backwards until I remembered the info to open the throttle about 1/4". Then started ok every time. Numbers with a Xoar 19x8 prop were: idle @ 1900 and top at 7080 (running a little rich). First flights tomorrow weather permitting.
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Old 12-16-2011, 08:58 AM
  #190  
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Default RE: OS GT33 33cc gasser

Awesome looking bird Capt G!

Steve


ORIGINAL: Capt G

First runs today on the OS GT-33. Very easy to start but first starts ran backwards until I remembered the info to open the throttle about 1/4''. Then started ok every time. Numbers with a Xoar 19x8 prop were: idle @ 1900 and top at 7080 (running a little rich). First flights tomorrow weather permitting.
Old 12-16-2011, 09:12 AM
  #191  
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Default RE: OS GT33 33cc gasser

Thanks. Didn't get to fly it yet. This engine hand starts very easily - in fact - I haven't even had the starter on it. My one complaint is the crankshaft thread size - 5/16 - 24. Why OS chose this size when all the props come with 10mm holes? This means you have to shim the props - very inconvenient.
Old 12-16-2011, 09:14 AM
  #192  
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Default RE: OS GT33 33cc gasser


ORIGINAL: Skaluf

Awesome looking bird Capt G!

Steve


ORIGINAL: Capt G

First runs today on the OS GT-33. Very easy to start but first starts ran backwards until I remembered the info to open the throttle about 1/4''. Then started ok every time. Numbers with a Xoar 19x8 prop were: idle @ 1900 and top at 7080 (running a little rich). First flights tomorrow weather permitting.
Don't know how you are related to Hobbico Steve.... Maybe you can light a fire under Hobby Services.

Spoke to them again yesterday with the same outcome...No engine repairs have been completed, and backplate is coming from Japan. When I quizzed them about why they would run an engine with a broken backplate I didn't get a satisfactory answer; only that it ran fine, twice. Then the guy proceeded to tell me that I needed a starter to turn it over; Tower has the heavy duty starter and lipos and charger in stock. Pure, unadulterated Bovine Skat. Wanted me to buy another 200$ worth of stuff from Tower so that I can start this engine. I've been in this sport for 43 years and never have I encountered worse incompetence

Old 12-16-2011, 09:23 AM
  #193  
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Default RE: OS GT33 33cc gasser

[/quote]
I've been in this sport for 43 years and never have I encountered worse incompetence
[/quote]

That is the experience I had with them with GT-55, and why I bought a DA-60 to replace it. I think OS makes some nice stuff, but they need a new US outlet for their products. BTW, I have a friend that had an almost identical experience with his GT-55 as well.

Old 12-18-2011, 10:44 AM
  #194  
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Default RE: OS GT33 33cc gasser

I recently ran my OS GT33 for the first time. I am using a home made isolator mount. It can idle around 1800 RPM but my mount shakes too much. I get a good reliable idle at 2300 RPM. I tested two props on the standard muffler. I got 7800 RPM with my 17-12 pattern prop. I am getting 7200 RPM with a Xoar 18-10 swoard. I too had to start at 1/4 throttle to keep it from running backwards. The engine is very easy to start. Attached are some photos of my set-up.
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Old 12-18-2011, 06:16 PM
  #195  
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Default RE: OS GT33 33cc gasser

You are running a GRP prop on that. How good an idea is that?

Ameyam
Old 12-19-2011, 02:58 AM
  #196  
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Default RE: OS GT33 33cc gasser

ORIGINAL: ameyam

You are running a GRP prop on that. How good an idea is that?

Ameyam
Nothing wrong with APC prop. Some may be slower to spool up than carbon or wood but they have very good airfoils and many times far superior performance over wood.

They do need to correct the reverse starting, change the start timing or something. My larger glow engines used to do that when flooded so I'd flood them and bounce'em off compression backwards and they'd start fine every time.
Old 12-19-2011, 05:42 AM
  #197  
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Default RE: OS GT33 33cc gasser

Basically, SI engines need to be set to fire (produce the spark) a few degrees after the piston has passed TDC. That way, the momentum of the piston (and hence the direstion of rotation) is maintained. This time gap between the piston reaching TDC and the firing of the plug is called ignition delay. The igition delay should be such as to maintain the rotation but not so large that the spark plug fires after there is significant loss in compression as that leads to loss of power and inefficient combustion (smoke). Also, the spark must be produced so that there is sufficient time for the flame propogation (in the fuel air mix) while the engine is within its compression range (which is around 5-7 in gas engines, if I remember correctly. This is the sweet spot for max power). However, as the engine revs up or heats up, the ignition delay has to reduce (this is called advancing ignition) as the crank speed gives a shorter time for compression to be in the sweet spot. On the other hand, flame propogation time is fairly constant (it can be reduced by additives such as TEL). Thus there is a minumum ignition delay. This is also the reason why gas engines are limited in their max RPMs to around 8500 rpm or so.

Reverse starting happens because of pre-ignition in spark ignition engines. Preignition occurs when the plug fires before the piston reaches TDC pushing the piston in the opposite direction to that in which it is supposed to rotate. It usually happens because the ignition delay is not properly set for a cold low speed start. You will not see this problem if using a starter because the starter turns the engine over faster. When the engine backfires like this, it usually dies or auto corrects on the next revolution as the ignition fires at the correct time after TDC. However, if the ignition only counts time after TDC, it is possible to sustain the reverse rotation. Usually, cutting the engine and then restarting it in the proper direction after a reverse run will get it running correctly. Its jsut a matter of knowing what you are doing.

So much for theory, I hope they get the reverse running problem sorted out, I intend to get this engine soon

Ameyam
Old 12-19-2011, 06:26 AM
  #198  
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Default RE: OS GT33 33cc gasser


ORIGINAL: PlaneKrazee

ORIGINAL: ameyam

You are running a GRP prop on that. How good an idea is that?

Ameyam
Nothing wrong with APC prop. Some may be slower to spool up than carbon or wood but they have very good airfoils and many times far superior performance over wood.

They do need to correct the reverse starting, change the start timing or something. My larger glow engines used to do that when flooded so I'd flood them and bounce'em off compression backwards and they'd start fine every time.
X2 on the APC props. Lot's of guys running them without issue. Much sturdier than wood if flying off a rough grass field. My only cautions would be regarding balance (DO IT!!!), and careful removal of flashing/sharp leading edges.

Re: starting backwards, that used to be SOP on the big Supertigers! They'd start very easily, but opposite of the way they were flipped almost every time! So, didn't take many long to learn to flip them backwards. You didn't even have to go all the way through the compression stroke....
Old 12-19-2011, 10:00 PM
  #199  
racerman27410
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Default RE: OS GT33 33cc gasser

As sweet as this engine runs and carburates i can forgive the occasional starting backwards.... i honestly think it has to do with all the compression... once you pull the prop thru it will bounce back off the next compression stroke and start backwards.

Being left handed i can stand behind the wing and can get a really good stroke on the prop.... 95% of the time it starts correctly.

When my brother starts it from the front 2 out of three times it will start backwards.


i'm going to let him try the reverse flip tomorrow and see how that works.
Old 12-19-2011, 10:46 PM
  #200  
Capt G
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Default RE: OS GT33 33cc gasser

First flights today - plenty of power. No backwards starting if throttle is opened aprox 1/4. Engine runs very smooth.
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