SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
12-14-2009, 02:20 PM
#54
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RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
The theory is that with a T and blind end to the carb, the dead end can get gummed up. I've made the route from crankcase to inlet via the carb so all the whole route has flow all the time. I did this by putting two external taps on the lid of the carb.
Stock is glow. I am running 20:1 mineral oil and plain bearings as I don't have the facilities to fit needle rollers (nice job on yours by the way).
Carb is #28 with accelerator pump and this is vastly superior on this 4 stroke to any of the non-pumped versions I tried. Electric motor type pickup.
Power is slightly down on glow at 28 degrees timing. 7700 on 16*8 Graupner. Think I was getting something similar on an 18*8 on 5% glow but never tachoed it.
Idle speed is lower and is generally stronger.
Run it on the bench for an hour or so total now. Awaiting Santa for an airframe
Stock is glow. I am running 20:1 mineral oil and plain bearings as I don't have the facilities to fit needle rollers (nice job on yours by the way).
Carb is #28 with accelerator pump and this is vastly superior on this 4 stroke to any of the non-pumped versions I tried. Electric motor type pickup.
Power is slightly down on glow at 28 degrees timing. 7700 on 16*8 Graupner. Think I was getting something similar on an 18*8 on 5% glow but never tachoed it.
Idle speed is lower and is generally stronger.
Run it on the bench for an hour or so total now. Awaiting Santa for an airframe
12-15-2009, 07:19 AM
#55
RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
Doghome:
Thanks for the explanation. Due to not knowing your vernacular, I think I need an explanation to your explanation. So here are my questions:
What is the entire carb part #? (#28 doesn't mean enought to me). Is the accelerator pump difference from the fuel pump via pulse diaphragm we're all familiar with on standard Walbros?
Electric motor type pickup. What is this? Are you talking about the ignition pickup? How does this fit in with the carb you were discussing?
Were the non-pumped carbs similar to barrel type glo carbs with no fuel pump whatsoever? (but perhaps with gas-compatible orings?)
I get what you mean about the pump diaphragm non-fuel side getting gummed up. I don't know what tee you're talking about. The gumming occurs with one straight run from the crankcase to the pulse port inlet.
"from the crankcase to the inlet via the carb" is hard to understand. What does "via the carb" mean? How about sketching a labelled plumbing diagram, taking a picture of it, and posting it to the forum? I know that's a bit of trouble, but I think you're knowledge would be helpful since you've obviously been sucessful.
In return, I'm going partially disassemble my Saito to post a picture of the completed needle bearing modification. Note that the journal wall is a bit thin, but is wider than the standard lower rod journal wall thickness. Also, the backplate is shiny instead of black because it had to be faced off in the lathe to make room for the wider (thicker?) rod journal.
Much thanks.
Pull Up Now!
Thanks for the explanation. Due to not knowing your vernacular, I think I need an explanation to your explanation. So here are my questions:
What is the entire carb part #? (#28 doesn't mean enought to me). Is the accelerator pump difference from the fuel pump via pulse diaphragm we're all familiar with on standard Walbros?
Electric motor type pickup. What is this? Are you talking about the ignition pickup? How does this fit in with the carb you were discussing?
Were the non-pumped carbs similar to barrel type glo carbs with no fuel pump whatsoever? (but perhaps with gas-compatible orings?)
I get what you mean about the pump diaphragm non-fuel side getting gummed up. I don't know what tee you're talking about. The gumming occurs with one straight run from the crankcase to the pulse port inlet.
"from the crankcase to the inlet via the carb" is hard to understand. What does "via the carb" mean? How about sketching a labelled plumbing diagram, taking a picture of it, and posting it to the forum? I know that's a bit of trouble, but I think you're knowledge would be helpful since you've obviously been sucessful.
In return, I'm going partially disassemble my Saito to post a picture of the completed needle bearing modification. Note that the journal wall is a bit thin, but is wider than the standard lower rod journal wall thickness. Also, the backplate is shiny instead of black because it had to be faced off in the lathe to make room for the wider (thicker?) rod journal.
Much thanks.
Pull Up Now!
12-15-2009, 10:38 AM
#57
RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
ORIGINAL: gkamysz
What is your application for this engine? Did you find the friction bearing to be unsuitable?
What is your application for this engine? Did you find the friction bearing to be unsuitable?
12-15-2009, 02:08 PM
#58
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RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
ORIGINAL: Pull Up Now!
What is the entire carb part - WT38 (includes piston accelerator pump). 28/64ths bore size. Standard Diaphragm i.e. with no return spring.
Electric motor type pickup - Sorry, I knew what I meant [
]! Meaning accelerates like an electric motor with no stumbles or hiccups.
Were the non-pumped carbs similar to barrel type glo carbs with no fuel pump whatsoever? (but perhaps with gas-compatible orings?) - No, other walbro WT types in smaller and larger bores, but without the accelerator pump. The two strokes I have run fine on the non-accelerator type, but this four stroke would not tune up properly. A very rich idle was needed to get a reasonable transition.
I get what you mean about the pump diaphragm non-fuel side getting gummed up. I don't know what tee you're talking about. The gumming occurs with one straight run from the crankcase to the pulse port inlet. - I made two pump ports on the lid of the carb. This way the gas from the crankcase flows though the diaphragm chamber and there is no dead end in the pipework.
''from the crankcase to the inlet via the carb'' is hard to understand. What does ''via the carb'' mean? How about sketching a labelled plumbing diagram, taking a picture of it, and posting it to the forum? I know that's a bit of trouble, but I think you're knowledge would be helpful since you've obviously been sucessful. - I'll do a sketch.
In return, I'm going partially disassemble my Saito to post a picture of the completed needle bearing modification. Note that the journal wall is a bit thin, but is wider than the standard lower rod journal wall thickness. Also, the backplate is shiny instead of black because it had to be faced off in the lathe to make room for the wider (thicker?) rod journal. - I like that mod and I think you did well to squeeze that into the Saito [8D]
Much thanks.
Pull Up Now!
What is the entire carb part - WT38 (includes piston accelerator pump). 28/64ths bore size. Standard Diaphragm i.e. with no return spring.
Electric motor type pickup - Sorry, I knew what I meant [
]! Meaning accelerates like an electric motor with no stumbles or hiccups.Were the non-pumped carbs similar to barrel type glo carbs with no fuel pump whatsoever? (but perhaps with gas-compatible orings?) - No, other walbro WT types in smaller and larger bores, but without the accelerator pump. The two strokes I have run fine on the non-accelerator type, but this four stroke would not tune up properly. A very rich idle was needed to get a reasonable transition.
I get what you mean about the pump diaphragm non-fuel side getting gummed up. I don't know what tee you're talking about. The gumming occurs with one straight run from the crankcase to the pulse port inlet. - I made two pump ports on the lid of the carb. This way the gas from the crankcase flows though the diaphragm chamber and there is no dead end in the pipework.
''from the crankcase to the inlet via the carb'' is hard to understand. What does ''via the carb'' mean? How about sketching a labelled plumbing diagram, taking a picture of it, and posting it to the forum? I know that's a bit of trouble, but I think you're knowledge would be helpful since you've obviously been sucessful. - I'll do a sketch.
In return, I'm going partially disassemble my Saito to post a picture of the completed needle bearing modification. Note that the journal wall is a bit thin, but is wider than the standard lower rod journal wall thickness. Also, the backplate is shiny instead of black because it had to be faced off in the lathe to make room for the wider (thicker?) rod journal. - I like that mod and I think you did well to squeeze that into the Saito [8D]
Much thanks.
Pull Up Now!
12-15-2009, 02:17 PM
#59
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RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
This is my crankcase vent/pulse line setup. There are no T pieces and therefore no dead end for oil to sit in.
12-16-2009, 09:19 AM
#60
RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
Thanks for the diagram and explanation. Now it's quite clear how you've set this up. Question: Have you ever tested this setup to see how it deals with oil in the primary pulse line? For example, actually placed some oil in the line to see how it travels thru the system? Secondarily, have you ever put a tee and a pressure guage on either of the two lines (pulse and/or the "drain" tube) to see the extent, if any, of pressure loss from the presense of the "drain"?
12-16-2009, 02:13 PM
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RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
I didn't put much specification, detail design, review, verification or validation effort into this project. The commercial, technical and third party risks were low........
Against what data or standard would I perform the pressure tests?
Cue:- Roll Eyes Smiley
(it's still smiling though!)
Dead end + Cold and old stagnent oil = possible blockage.
Through path and no oil trap = probably no blockage.
I can see oily fumes moving along the pipes if that's what you mean!
Against what data or standard would I perform the pressure tests?
Cue:- Roll Eyes Smiley
(it's still smiling though!)Dead end + Cold and old stagnent oil = possible blockage.
Through path and no oil trap = probably no blockage.
I can see oily fumes moving along the pipes if that's what you mean!
12-18-2009, 12:47 PM
#64
RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
ORIGINAL: w8ye
he's getting there
he's getting there
Update: The 16x1mm tap and die have arrived, so this weekend I'll get the intake extension done, and braze in a tube for a vacuum tap. Material is brass. Yes, heavy, but pretty small. If I can find a threaded barb somewhere, I'll revert to aluminum material and tap the barb hole. Probably some smart person out there could ask "if you can machine an extension, why can't you just machine your own barb too?". Good point. OK I'll do it.
I'm hoping the carb diaphragm return spring will arrive today, too. If all this happens, there's no reason why a first test couldn't be done on Sunday 12-20-2009.
12-18-2009, 01:05 PM
#65
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RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
Let us know how it goes [sm=thumbup.gif]
I'll try and get a better video of mine running than the one I have from my 5 year old phone! Quite happy with the accelerator pump [&:]
P.S. I'm an engineer, so please expect 'banter' in all posts
I'll try and get a better video of mine running than the one I have from my 5 year old phone! Quite happy with the accelerator pump [&:]
P.S. I'm an engineer, so please expect 'banter' in all posts
12-18-2009, 01:31 PM
#67
RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
ORIGINAL: Pull Up Now!
Who's the "he"?
Update: The 16x1mm tap and die have arrived, so this weekend I'll get the intake extension done, and braze in a tube for a vacuum tap. Material is brass. Yes, heavy, but pretty small. If I can find a threaded barb somewhere, I'll revert to aluminum material and tap the barb hole. Probably some smart person out there could ask "if you can machine an extension, why can't you just machine your own barb too?". Good point. OK I'll do it.
I'm hoping the carb diaphragm return spring will arrive today, too. If all this happens, there's no reason why a first test couldn't be done on Sunday 12-20-2009.
ORIGINAL: w8ye
he's getting there
he's getting there
Update: The 16x1mm tap and die have arrived, so this weekend I'll get the intake extension done, and braze in a tube for a vacuum tap. Material is brass. Yes, heavy, but pretty small. If I can find a threaded barb somewhere, I'll revert to aluminum material and tap the barb hole. Probably some smart person out there could ask "if you can machine an extension, why can't you just machine your own barb too?". Good point. OK I'll do it.
I'm hoping the carb diaphragm return spring will arrive today, too. If all this happens, there's no reason why a first test couldn't be done on Sunday 12-20-2009.
12-18-2009, 01:58 PM
#68
RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
ORIGINAL: dogshome
Don't think there is much chance of fitting a needle roller in here :-(
Don't think there is much chance of fitting a needle roller in here :-(
12-18-2009, 02:46 PM
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RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
Point and shoot very compact camera Panasonic DMC-F55 10M pixel (although pixel count doesn't mean a lot for quality these days!). Full auto settings. 50W Halogen desk lamp above the engine in the pic and normal flourescent tubes in the garage.
It's very good camera at close-ups and sunny outdoor pics. Low light and cloudy is poor and zoom for catching flying models is nowhere near enough!
Colours are good. There is a bit of fish-eye distortion visible on outdoor pics with straight lines as it's only a small lens.
I robbed the rod picture above, but the rest are mine.
My camera:-
Micks BIG heli up close with good light.
Terrys Extra230 in very good light.
It wasn't as dark as it looked and I had to have a fast shutter to catch the heli.
Bits of distortion just visible here.
These ones from my friends digital SLR - spot the difference!
My Yak at long distance on a cloudy day. This is a 'cut' out of a much bigger picture.
My tiny 4G3 moving quickly at maybe 20M
(My plane again) Megawot towing 4.6M glider quite a long...... way away.
Off topic? me?
It's very good camera at close-ups and sunny outdoor pics. Low light and cloudy is poor and zoom for catching flying models is nowhere near enough!
Colours are good. There is a bit of fish-eye distortion visible on outdoor pics with straight lines as it's only a small lens.
I robbed the rod picture above, but the rest are mine.
My camera:-
Micks BIG heli up close with good light.
Terrys Extra230 in very good light.
It wasn't as dark as it looked and I had to have a fast shutter to catch the heli.
Bits of distortion just visible here.
These ones from my friends digital SLR - spot the difference!
My Yak at long distance on a cloudy day. This is a 'cut' out of a much bigger picture.
My tiny 4G3 moving quickly at maybe 20M
(My plane again) Megawot towing 4.6M glider quite a long...... way away.
Off topic? me?
12-19-2009, 07:56 PM
#71
RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
Back home. Got a chance to really look at your terrific pictures. I really like the Bell Heli, if that's what it is. All that's needed are some Viet Cong running around. Thanks for the diversion from the heady subject of engine conversions. (pun!!!! ha!) Humor can be as exhausting as it is manifold. [:-] That glider must be huge. 15 ft by my conversion.
I did build the carb extension for the Saito 1.5 conversion so it's Walbro would sit vertical behind the head. Attached are some pics of that. I'm pretty happy with the results. Decided on brass in case brazing the tube was necessary. It wasn't, but a secondary reason is I had a latent fear that aluminum-on-aluminum would gall the threads.
Unfortunately the carb "4 stroke conversions springs" didn't come in the mail, so the engine won't run this weekend as I'd hoped. What did arrive is a little paper from the mailman saying they tried to deliver it but a signature was required. These springs are 47 cents each. I think it's more likely the 30 ft from the street looked daunting to the mailman. I think this is what government health care will look like to us in a year. [>:]
I did build the carb extension for the Saito 1.5 conversion so it's Walbro would sit vertical behind the head. Attached are some pics of that. I'm pretty happy with the results. Decided on brass in case brazing the tube was necessary. It wasn't, but a secondary reason is I had a latent fear that aluminum-on-aluminum would gall the threads.
Unfortunately the carb "4 stroke conversions springs" didn't come in the mail, so the engine won't run this weekend as I'd hoped. What did arrive is a little paper from the mailman saying they tried to deliver it but a signature was required. These springs are 47 cents each. I think it's more likely the 30 ft from the street looked daunting to the mailman. I think this is what government health care will look like to us in a year. [>:]
12-20-2009, 06:47 AM
#72
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RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
RE: Viet Cong. I already did a little photoshop for my friend Mick!
Nice job on the threaded adaptor and the ally carb fitting. Looks like it should work well.
Offer 'postie' some christmas sweets next time you see him, might make the difference next time
Nice job on the threaded adaptor and the ally carb fitting. Looks like it should work well.
Offer 'postie' some christmas sweets next time you see him, might make the difference next time
12-20-2009, 09:35 AM
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RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
Unfortunately the carb "4 stroke conversions springs" didn't come in the mail, so the engine won't run this weekend as I'd hoped.
12-20-2009, 10:52 AM
#74
RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
Yeah, I thought of running it anyway. But it's snowing outside and darn cold in the garage. I'm cooking up a method to run engines in the basement using the household pressure equalization tube (already installed in every home) as a forced ventilator for the exhaust. It would be handy for half the year...could put a couple discarded computer muffin fans for positive outward flow.
Anyway, plenty of projects to keep busy. I flipped my 40 sized cub on skiis in the snow on Friday. A group of us guys at work fly during lunch. These are made by Maiden Model Products http://www.maidenusammp.com but the tension spring keeps popping out of the retention groove. Upon landing, the forward end dug into the ground like a javelin, flipping the cub. So I've been busy rigging up a crude fix, shown here in the picture. My piece of it is that horizontal spring guide. Perhaps will try it again later. Fresh snow, too!
Anyway, plenty of projects to keep busy. I flipped my 40 sized cub on skiis in the snow on Friday. A group of us guys at work fly during lunch. These are made by Maiden Model Products http://www.maidenusammp.com but the tension spring keeps popping out of the retention groove. Upon landing, the forward end dug into the ground like a javelin, flipping the cub. So I've been busy rigging up a crude fix, shown here in the picture. My piece of it is that horizontal spring guide. Perhaps will try it again later. Fresh snow, too!
