Stephens knuckle head build

[dnalot]

Hi

Could you fill a built-up float with loose micro-balloons? That way even if a seam leaked you couldn't lose much floatation. As long as you didn't use any binder when installing the micro-balloons you wouldn't be adding that much extra weight to the float. Of course if the seam split open wide enough you'd have micro-balloons throughout your carb/engine.

The balloons when mixed with a very small amount of resin will be extremely strong. I used to make balls the size of a tennis ball and when cured I could hurl it as hard as I could on the ground and not chip it.

I would mold the float with a brass hinge cast into the part.

 

[Hopper]

Be careful not to get too much solder on the brass strips if you go that route. Stuff is darned heavy. It might be worth making a simple die press a circular piece of shim into shape and then solder two together, two joint only and therefore 50 per cent less solder.

The die could be as simple as two flat plates bolted together with a piece of annealed brass shim in between.
The lower plate would have a circular groove turned in it, the size and shape of the float. The upper plate would have a hole drilled and reamed directly above that groove so a punch with a raised ridge that fits in the bottom groove on the lower end of it.

That's how the Indians make the full size repops for Linkert carbs.
You can see below they lay a lot of solder on them and they are notorious for being heavy and prone to leaking.

 

[Bowtie41]

Hopper,
I agree,I was just thinking of something simple and no diework.But hell,he's in deep enough already,lol.Your solution is definately lighter than mine,but I'd dremel/file away as much excess as possible.For yours,I'd probably whip it up outta wood with a ball end mill for the female,and spray it with something as a mold release,and use Bondo or epoxy in it to make the male part.

 

[ddmckee54]

However you make it, use the thinnest material that you can find. The calculations that I did, using 0.010" brass to construct a torus, showed that the volume of fuel displaced weighed only marginally more than just the brass used to make the torus. My calculations were made using a torus with a 1"ID and a 2"OD, I also used the entire volume of the torus to calculate the fuel displaced. You need it floating, not submerged, so it would be displacing much less volume and generating much less lift.

Don

 

[Cogsy]

If the thing really is almost balanced with lift vs weight, it's not going to put much pressure on the needle and seat and will be unlikely to stop fuel flow I would imagine.

 

[driller1432]

The float that won't so guys I made a die out of plastic and stamped out float halves out of .010 brass the center would not draw out enough so had to solder strip to inside of float
View attachment ImageUploadedByModel Engines1455848213.085062.jpg
View attachment ImageUploadedByModel Engines1455848265.682119.jpg
View attachment ImageUploadedByModel Engines1455848291.748865.jpg
Got it all soldered together cleaned most of solder off and a quick toss in water, good bye slowly floated to bottom. This isn't going to work so nitrophyl is up next. View attachment ImageUploadedByModel Engines1455848834.270350.jpg
Thanks all you guys for your help we will make something work!

 

[Bowtie41]

That looks awesome,Great Job!!:bow:If tearing is still a problem,anneal it(see youtube) 1st.

 

[Hopper]

Try again with .005" brass shim? Half the weight. (Assuming your float "floated to the bottom" due to weight rather than a small leak. If the latter, a smear of epoxy in the right place should fix.)

You might get more of the middle part if you reduce the diameter of the guide pin and start with a smaller hole in the blank shim, allowing more metal to flow up into the inside wall.

That motor sure is looking purty. Looking forward to seeing/hearing the video of it running.

 

[Hopper]

Can someone post a link to the full set of Knucklehead plans please? I dont seem to be able to find them, only a few individual pages in various threads. Probably just my computer illiteracy...

 

[Bowtie41]

From page 7 of this thread

Try this
http://www.homemodelenginemachinist.com/downloads/draw-tech-297.html

 

[driller1432]

3D printer could a float be printed out with a 3D printer?

 

[Draw-Tech]

Hi Steve

Carb. looks great. I think if we can find a plastic that would not dissolve in gas, I can print it. I will try to dissolve some of the materials I have, maybe polypropylene. Does the float float? What about a ring of .005 brass, with good old cork bonded to it?
Jack
Draw-Tech

 

[Hopper]

Thanks Bowtie. I knew it was somewhere but danged if I could find that link, or the downloads section. All good now, mate.

 

[Hopper]

Doh! I spoke too soon. When I follow that link, I get a blank page.
Also I can't see a download section of the forum anywhere.
Do I need to be a financial member to use the downloads, or do I have a computer problem?
I'm pretty sure I downloaded some of the drawings some time back, by following that link, but not anymore.

 

[pickleford75]

An old timer once told me that he made replacement floats out of balsa and coated with a sealer..... never tried it but who knows

 

[crankshafter]

Same here . When I go to downloads it showing only a blank page.
cs.

 

[ozzie46]

(Same here . When I go to downloads it showing only a blank page.
cs.)

Same here too! What gives???


Ron

 

[petertha]

If I understand the issue - anything you 'add' to the brass shim box shell like cork, foam, microbaloons..) is added weight. Added weight in any form is less buoyancy vs. a sealed box of air. So the options are:
- less dense shell material (aluminum? plastic?)
- larger footprint volume of float
- lighter gas filled float ...now THAT would be tricky

So yes, if the sealed balsa shape weighted less than the brass box, it would be more buoyant all things being equal. Practicality wise, pros & cons, that's a different issue.

 

[Draw-Tech]

Doh! I spoke too soon. When I follow that link, I get a blank page.
Also I can't see a download section of the forum anywhere.
Do I need to be a financial member to use the downloads, or do I have a computer problem?
I'm pretty sure I downloaded some of the drawings some time back, by following that link, but not anymore.

Hi Hopper
I checked out the site, had same problem, I have sent a message to the administrators about the problem.
JACK
DRAW-TECH

 

[Bowtie41]

Hey Guys,
Just looked and found same thing.For now try this link:
http://www.homemodelenginemachinist.com/search.php?searchid=865554

It list all posts Jack made to the Plans forum.I could narrow it down more,but it would take awhile(only 69 links),and there is so much good info other than prints to look at.

Jack,thanks AGAIN for sharing all of this!!!Can't wait til I get caught up here,if ever,to start a build of my own.