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HelicopterGasser Model RC HelicoptersOther › Suitable carb ?
01-01-2010 05:04 PM  7 years agoPost 1
cliffbarrimore

rrApprentice

Welcome Bay, Tauranga, New Zealand

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Hi All

Doing a glow to gas conversion, I am going to use the standard OS carb for a start point, But I was thinking of a Walbro type carb further down the line..

Now this engine is quite small <10cc .... Anyone know of a small size Gasoline carb, not bothered about fitments I can Bodge something together to make it connect to the engine.

someone mentioned the Walbro wta-2 but cant find any specs for it...

thanks

Cliff

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01-01-2010 07:28 PM  7 years agoPost 2
rccarguy

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Boston MA

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You need a setup something like this...

Nitro carb won't work very well if at all, the tuning will be a bear to get right and you'll likely torch the piston and ring before you get it right, needle settings are d**m finicky on converted engines as I found out first hand.

XCell Spectra G
Radikal G20
Some obsolete nitro helis too...

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01-01-2010 08:02 PM  7 years agoPost 3
Sean Bosse

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Germantown, MD.

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I think it mostly has to do with the appropriate air fuel mixture. Methanol typically needs to be run in the realm of 6:1 give or take a few points. Gas on the other hand runs happily at about 11.5:1 for peak power. Also, you need to take into consideration the cooling required for a gas engine as oppose to a methanol engine. Methanol burns significantly cooler than petrol, therefore needing less surface area for cooling than a gas engine. Not sure if this helps. Good luck with your conversion, and keep us posted.

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01-01-2010 08:45 PM  7 years agoPost 4
cliffbarrimore

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Welcome Bay, Tauranga, New Zealand

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Hi Those Pictures are pretty much what I want to do,
Whats the engine size of that and what carb are you using

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01-01-2010 08:54 PM  7 years agoPost 5
rccarguy

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Boston MA

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Whats the engine size of that and what carb are you using
The engine is a BME G90 http://www.bmeengine.com/

I just took it out of the box and looked, no markings or numbers on the carb that I can see, so I have no idea what it actually is.

XCell Spectra G
Radikal G20
Some obsolete nitro helis too...

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01-02-2010 06:08 PM  7 years agoPost 6
cliffbarrimore

rrApprentice

Welcome Bay, Tauranga, New Zealand

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No problem, I am going to stick with the carb on the engine to start off and see what happens, then maybe later see what I can knock up and what works, I guess its going to need to be weaker than on Nitro, currently runs at 3/4 turn out, I wonder if there will be enough range on the carb, Going to order the bits from justengines next week

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01-03-2010 03:11 PM  7 years agoPost 7
GMPheli

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W. Bridgewater, MA USA

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Don't you need a conrod with needle bearings to run gasoline?

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01-03-2010 04:59 PM  7 years agoPost 8
cliffbarrimore

rrApprentice

Welcome Bay, Tauranga, New Zealand

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Maybe, I can see the reasons why you would use needle rollers, and also reasons not to, Gasoline is more oily than Nitro, which is why Nitro is run at about 4 or 5 to 1 ratio and it takes the excess heat out with it, I plan on running a fairly high oil ratio and see how it runs, as long as oil is getting to the surfaces to lubricate them and the engine is not running lean, I cant see there being a big issue, I dont do 3D so I am not stressing the engine excessively. if the engine dies then it can be rebuilt. I used to run my Zenoah on AMSOil at 100 to 1 ratio where its stated that is should be 20-25 to 1, and there is oil available for mixes at 150 to 1, So I think a lot of it will be down to the quality of 2 stroke oil used. I still have 4+ litres of AMSOil 100-1 and various other makes so I will see how they run.

if someone makes a needle roller small enough for the OS 50 bottom end then I'll try it, but it will still need Lube.

Look at a car engine, OK its bottom end is in oil, but the bearings are only shells, no balls, no needles.

I have no Idea on the run times expected, I get 20 mins out of a tank of 12% nitro now on the Hyper 50 in my rex 600, so could be very interesting, Hope to order the parts Monday!

Just found this which explains quite a lot

http://www.rcmodelreviews.com/goodoil.shtml

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01-03-2010 05:42 PM  7 years agoPost 9
rccarguy

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Boston MA

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Look at a car engine, OK its bottom end is in oil, but the bearings are only shells, no balls, no needles.
But those are pressure fed from the inside, that's why they can run tight tolerances in automotive applications.

From my direct experience with the BME G90, I can tell you you're fighting an uphill battle, roller bearings would certainly be a "good thing".

XCell Spectra G
Radikal G20
Some obsolete nitro helis too...

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01-03-2010 06:14 PM  7 years agoPost 10
cliffbarrimore

rrApprentice

Welcome Bay, Tauranga, New Zealand

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Yep you maybe right, but if it all messes up, the bits can be replaced and I'll try something different, I just hate the zenoah engines (that'll get people going) I had a Predator Gasser with a Hanson G26 engine and it was awful, got through 2 carbs, I had similar problems with a Zenoah powered car,Just ran lean all the time, I see load of people on here with similar problems with Zenoah (and many who have no problems too), I just want to try something different and Cheaper, and yes you could say the zenoah problems were down to me, but I had many 'experts' look at it and none to get either to run consistantly, Should leave then in the strimmers where they belong

I think if I can get a good quality oil at the right mix, it will work, Gasoline is more oily so I have a good head start. 40-1 with the Amsoil 100-1 is where I have been pointed as a good start point and weaken from there, its only a bit of fun and everyone seems to get too serious and say things cant be done.

We'd still have candles if it wasnt for Eddision trying and trying to make the electric bulb (or was it someone else?)

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01-03-2010 07:29 PM  7 years agoPost 11
rccarguy

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Boston MA

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We'd still have candles if it wasnt for Eddision trying and trying to make the electric bulb (or was it someone else?)
True, you won't get anywhere if you don't try!

As you can see from the previous pictures, I installed a converted 90 in a Fury Expert, trying to build a gasser on the cheap. It did run and fly a bit although no where near what I had hoped it to be. Biggest problem was trying to keep it cool along with very touchy carb tuning, I eventually went back to nitro power in the Fury and bought an RTF Spectra G.

If you think a Zenoah was a bear to tune, you'll look back and see it wasn't all that bad compared to what you're building. The converted nitro motors are way more sensitive to tuning on gasoline and they will burn up in the blink of an eye if you get it wrong, don't ask me how I know...

Good luck, let us know how it turns out.

XCell Spectra G
Radikal G20
Some obsolete nitro helis too...

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01-04-2010 01:09 AM  7 years agoPost 12
windy62

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USA

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Gasoline is more oily than Nitro
You can tell by all the mess that's all over the Gasser, whereas the Nitro is always clean as a whistle...

Or is it the other way 'round...

windy62

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01-04-2010 01:36 AM  7 years agoPost 13
Fixit

rrElite Veteran

UK

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Or is it the other way 'round...
That’s a hard one because my whistle is never clean either

I only like to fly gassed up

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01-14-2010 05:04 PM  7 years agoPost 14
cliffbarrimore

rrApprentice

Welcome Bay, Tauranga, New Zealand

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does anyone do a fitment for sticking a zenoah carb on a OS engine, I keep seeing the same fitment on lots of conversions, but not found anything on the http://www...

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01-14-2010 08:58 PM  7 years agoPost 15
rccarguy

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Boston MA

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does anyone do a fitment for sticking a zenoah carb on a OS engine, I keep seeing the same fitment on lots of conversions, but not found anything on the http://www...
I don't know of any off the shelf conversions parts available, the only ones I've dealt with have been as part of an overall gasoline conversion where you buy the engine already converted. You're pretty much on your own to fabricate the needed bits as there aren't many shops that do these conversions, I can count the number of them I know of on one hand and have fingers left over.

That said, there are three things required to make a gas conversion work, an adaptor plate to bolt the carb onto and then sit into the crankcase as per the stock carb fitment, add a pressure port to the crankcase to allow the diaphram pump to work, and an ignition trigger of some sort. The adaptor can be made easily enough if you have access to a metal lathe or have a friend who works as a machinist that can do it for you. The pressure port is nothing more than drilling a hole in an appropriate spot, cutting a bit of threads in the hole, and using a nitro muffler pressure fitting. Triggering the spark ignition system can be done using a govenor magnet set into the crankshaft collar, you'll need to use a degree wheel to determine where to put it. Here's a pic of my converted Super Tiger 90, you can see the fitting for the pressure port, a bit of the carb mount adaptor, and the crankshaft mounted magnet for the ignition module. Sorry about the pic quality, the batts are dying in the camera and the focus goes soft when that happens...

P.S. the carb on this engine is a Zama, it's a bit smaller than the Walbros on either of my gassers and probably better suited to the smaller displacement. I found these numbers on it M27D over 79A...

XCell Spectra G
Radikal G20
Some obsolete nitro helis too...

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01-15-2010 02:22 AM  7 years agoPost 16
Justin Stuart (RIP)

rrMaster

Plano, Texas

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That conversion seems like a lot more trouble than it's worth. But it's interesting. I hope you can get it to work.

Avant RC
Scorpion Power Systems
Thunder Power RC
Kontronik Drives

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01-15-2010 03:27 AM  7 years agoPost 17
rccarguy

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Boston MA

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That conversion seems like a lot more trouble than it's worth. But it's interesting. I hope you can get it to work.
They actually work quite well in airplane usage, but for heli use cooling becomes an issue, converted nitro engines don't have nearly enough fin area to cool properly inside a heli frame. On the front of a plank with a prop blowing air across the cylinder and head you can get away with it. I was never able to get the ST 90 to run cool enough to keep from cooking when I had it in the Xcell Fury, plus it was lacking in power compared to a nitro engine.

XCell Spectra G
Radikal G20
Some obsolete nitro helis too...

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01-15-2010 09:39 AM  7 years agoPost 18
cliffbarrimore

rrApprentice

Welcome Bay, Tauranga, New Zealand

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Hi Thanks for the info on the carb

I have just got the bits in the post, I shall have a play over the coming weeks and see how it all works. I shall initally use nitro with the cdi ignition just to see how it all runs, then add shims to the head and run gas/oil mix, seeing as its only a 50 size engine and is not stressed at all and the only power I need is to get it off the ground and soberly move around the sky, But thats what I like about RC stuff, you can experiment and develop things. I have people at my club who can only see the mainstream stuff and have to buy the latest bling and fastest servos, best exhaust, powerfullest engines, and then they just hover, not that I can fly any better, I just like to mess with things ..

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01-20-2010 01:21 AM  7 years agoPost 19
ChrisJ

rrNovice

MI

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C1Q-M27D $ 38.10 from Zama but it is probably to large for what your trying to do.

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