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Post  rdw777 Thu Mar 11, 2021 2:24 pm

Hi guys.....

I am putting together an .049 engine with a throttle ring after about a 20 year absence from gas power.... From my small collection of engines and parts from long ago... Would like your thoughts..... The intended job duty would be for a typical 1/2 A hi wing rc trainer type... 230 or so sq in.... 36” WS.... 16-18 oz

So far I have .....tapered crank case, #3 two bypass cylinder with SPI ground for throttle ring, Throttle ring, Horseshoe back plate with clean copper reed and fine needle.... An old Perfect type tank about 16 cc’s

The throttle ring has the adjustable clip (which I like) but is not the typical slotted type. It has two holes 180 degrees apart that are .152” in diameter....I looked around on the forum a good bit on throttle rings but have not found this one
yet.... Anyone know what it came from? Seems like small openings compared to the cylinder ports....

I have read on the forum about throttle rings and SPI.... Most say not good but a few say OK.... Thoughts?....Options for me might be to dig up a non SPI cyl..... I would just run what I have and see with about a 6-3 prop but don’t have any fuel yet..... btw, I guessing 25% nitro with castor/synthetic equal parts?

Not looking for super low idle..... Just something to hold altitude or descend..... Just putter around...,,Then kill it with the trim button...,

Thanks!!
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Post  davidll1984 Thu Mar 11, 2021 4:44 pm

No dont change that seting is just Perfect for the application i asume its Not for speed so rc ring wil do the job in case its Not working correct try one new ring as mabe is home made and posible reduce power try the larger opening one wort the time To Find one from jerobee .049 engines wil Not change its top rpm down idle RC Plane just wat it need use non spi wit carb like surestart or the other carb that fit
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Post  Lukemiester Thu Mar 11, 2021 8:39 pm

Sounds to me like you got a nice engine setup! If it were mine, I’d probably change it a little bit cuz more fast=more cool Very Happy
Like David said, it won’t be incredibly fast, but it will be a nice little powerplant for whatever it’s going on Thumbs Up
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Post  rdw777 Fri Mar 12, 2021 9:54 am

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Here are photos of the throttle ring/cylinder and assembled engine.... The cyl is 2 port with SPI.... Anyone know what the throttle ring was on originally?.... Think it will kill top end much?...... Still waiting on fuel and gaskets for live testing....
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Post  davidll1984 Fri Mar 12, 2021 11:08 am

Y have two model and one lose rpm the one u have sur it wil lost power New User - Engine Build 16155610
The one u have look home made ?it wil work
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Post  bakergw Fri Mar 12, 2021 1:57 pm

Hi rdw,

I agree pretty much with all of the above. The engine needs to be built to meet your needs which may include other constraints such as muffler or not depending on rules etc. where you fly and such. I am very much of the view the engine needs to suit you and what you intend to do with it. There is heaps of excellent very very technical stuff on this forum which is also very useful in helping build a motor that suits your needs depending on what they are. I have several engines that are very much steady as she goes engines, start super easy, heaps reliable, dont munch plugs, and fly my plane the way I want to fly my plane they are in. Just like you are describing your engine.

I also have several motors that are hand grenades and also are great for what I want from them, most of the minor tweaks to get these engines going like hand grenades came from great info on this site, as did ideas on how to get these motors to last longer etc.

Read-in, ask questions on the forum , weigh up the pros and cons for your situation and have a bloody great time flying again. RC Plane Flying and trying out different ideas and see how they go for you. Returning to flying and building planes and engines is the best thing Ive done for my head in over 40 years Old Bugger cheers lol!

Cheers,
Gary
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Post  Oldenginerod Fri Mar 12, 2021 4:15 pm

@rdw777 wrote:New User - Engine Build 804dc910
New User - Engine Build 94f25910

Here are photos of the throttle ring/cylinder and assembled engine.... The cyl is 2 port with SPI.... Anyone know what the throttle ring was on originally?.... Think it will kill top end much?...... Still waiting on fuel and gaskets for live testing....

I don't believe it's home made like suggested. I have one exactly the same with the round holes. I doubt that there would be much loss of power at full throttle apart from maybe a slight reaction to the narrow outlet recirculating exhaust gasses through the SPI.
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Post  sosam117 Fri Mar 12, 2021 9:34 pm

The round hole throttle ring was Cox's first try at it.
It was cheaper to just drill a hole compared to the later versions that had to be inserted into a mill to cut the slots (180degrees from each other.

The early round hole throttle ring was just to prove the concept of rpm reduction.
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Post  rdw777 Sat Mar 13, 2021 2:23 am

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That’s good to know the history of the ring and thoughts how it may work, Thanks!

I attached a piece of fuel line about 4” long and put the other end in a cup with alcohol.... Picks it up real easy with a finger choke on the venturi....I may try to fab up a mount so I can keep this feature when installed on the plane

Got the tank cleaned up, Was very gunked up.... Soaked it acetone for three days then used a syringe to pump thru all the ports.....Also submerged and leak checked it...Ports were then plugged with tubing then a good exterior cleaning/polish with Brasso....
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Post  944_Jim Sat Mar 13, 2021 6:45 am

No need to fab a mount to begin the duel draw.

Once your tank is full, put your finger on the vent line, and give the fill line a bit of pressure. The pressure will push fuel to the venturi. Release your finger from the vent, remove your fuel filler, and "start your engine!"

Oh, and there is (are?) an app that uses your phone as a tach. I use RPM Gauge, but then I'm Android-based.
Benchmount your new toy, and use the app to "listen" and display your RPMs. This way you can get a high-speed run and slow, and know just how much that throttle ring slows it down.
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Post  rdw777 Sun Mar 14, 2021 5:42 pm

Thank Jim for some more tips, That is appreciated!!!

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While waiting for gaskets and fuel I tried to make a Venturi extension..... The plane I’m wanting to build originally called for a Space Hopper which looks kind of cool but I’m fresh out of one.... Smile
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Post  rdw777 Sun Mar 14, 2021 5:56 pm

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It was made coating a wooden mandrel with JB Weld spinning on a drill press using the the lost balsa method (I just made that up Very Happy)..... It slips over the factory housing and I will silicon it in place after testing without first...

I’ll have to fab a mount to accommodate this set up..... I’m thinking some 1/2” aluminum angle arranged in two pieces like a clamshell to slip on to the 1/8” ply mount on the plane....Hopefully it will stand up to raw fuel.... I’ve read about JBW being used on carbs and stuff....

I’ll post some more build it fotos if anyone is interested...
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Post  Lukemiester Sun Mar 14, 2021 7:07 pm

Cool idea! I’d like to see if it makes a difference
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