Prop re-pitching and casting.

[Tim Kish]

Idealy you need a gap between the parts being soldered, preheating the fixture won't fix the problem you have.

The solder will only flow were it can and if the two pieces are tight together it will never find it's way between them.

Would be nice if your fixture allowed the blade to move away from the hub until solder is applied and then forced back against the hub mating the two parts with solder between them.

Tim

 

[Marty Davis]

Terry:

Dee Hughey used a MAP Gas torch with "Dial-a-Prop" rather than the propane for that reason. He saw a great increase in the temp with the MAP Gas Torch. You might try that. Give Dee a call, he would be happy to help you. Everything is the same with MAP vs Propane, just the cylinder is different.

Dee also used a carbon rod so that it didn't heat sink. Maybe you could incorporate a carbon rod holder for the prop tips for the same reason. I have built hundreds of Dial a Props and the carbon rod was one of the real secrets.

 

[Ron Jefferson]

Would it be wise to grind an angle on the blades where they meet the hub? Just like welding, you would fill the gap with a filet of braze. Just a thought.

Ron

 

[coolhotrods]

Map gas is the way to go. I use it all brazing applications. Dustin

 

[Tim Kish]

Would it be wise to grind an angle on the blades where they meet the hub? Just like welding, you would fill the gap with a filet of braze. Just a thought.

Ron

Wouldn't hurt, the solder can only work if it gets between the parts being soldered and heat is crytical.

I have never used anything less than a good Oxy Acetaline torch at work and have solder just about every material I can think of.lol

 

[Tim Kish]

We typically heat up fixtures at work when soldering two different materials and it's more to control the cool down to help prevet things from twisting or cracking.

e.g. Carbide on Steel.

 

[Mike Larson]

You can buy a minuature Oxy/Acetylene kit at Home depot, etc, its rudimenary at best, and I buy my rods, depending on material at the welding supply store... ... I'd rather sweat than braze, but... steel to steel... burnt holes in alotta stuff....lol... You'll get it Terry... I learned alotta stuff that didnt work..... and it continues every day.... good luck... watching with interest... Mike

 

[dwilfong]

When I worked as a millwright I had to tungsten carbide hard face augers for a lime injector in a rock kiln.

The trick was to preheat the whole piece and not let it cool down as you worked the rod.

I used a #12 oxygen acetylene brazing tip to do this.

As Marty suggested a non heat sink fixture would keep the temps at a even state as you worked on the piece.

Try using a ceramic slip to hold the blades instead of the Cerro.

This is how thy cast the props.

 

[Terry Keeley]

Thanks for all the suggestions guys, always amazes me the level of knowledge around here.

Idealy you need a gap between the parts being soldered, preheating the fixture won't fix the problem you have.

The solder will only flow were it can and if the two pieces are tight together it will never find it's way between them.

Would be nice if your fixture allowed the blade to move away from the hub until solder is applied and then forced back against the hub mating the two parts with solder between them.

Tim

I bored the blade roots to final size with a tight fit (see post 19), maybe I should leave a couple thou per side next time? Was thinking of tinning both parts, then sliding the hub into place while hot and finally adding the fillet. Using "Easy-Flo 45", specs say a close fit is best, maybe the 35% alloy would be better?

https://www.lucasmilhaupt.com/en-US/products/fillermetals/silverbasedcadmiumbearingfillermetals/9/

Terry:

Dee Hughey used a MAP Gas torch with "Dial-a-Prop" rather than the propane for that reason. He saw a great increase in the temp with the MAP Gas Torch. You might try that. Give Dee a call, he would be happy to help you. Everything is the same with MAP vs Propane, just the cylinder is different.

Dee also used a carbon rod so that it didn't heat sink. Maybe you could incorporate a carbon rod holder for the prop tips for the same reason. I have built hundreds of Dial a Props and the carbon rod was one of the real secrets.

Did talk to Dee a bit and went with the oxy/propylene set up (post 26), propane wasn't hot enough. Dee did mention a carbon rod and it went right over my head. Ever do any BeCu props or were they all stainless?

Found this: http://www.beckergraphite.com/stock.html

Would it be wise to grind an angle on the blades where they meet the hub? Just like welding, you would fill the gap with a filet of braze. Just a thought.

Ron

That's a great idea, I'll cut a little 45* angle in the blades and fill with braze, thanks!

 

[Terry Keeley]

When I worked as a millwright I had to tungsten carbide hard face augers for a lime injector in a rock kiln.

The trick was to preheat the whole piece and not let it cool down as you worked the rod.

I used a #12 oxygen acetylene brazing tip to do this.

As Marty suggested a non heat sink fixture would keep the temps at a even state as you worked on the piece.

Try using a ceramic slip to hold the blades instead of the Cerro.

This is how thy cast the props.

What's a ceramic slip?

Actually the Cerro is melted away leaving just the 3 scew tips/side holding the blades in place so I don't think there's much heat lost to them.

The post is a different story tho...

 

[dwilfong]

When I worked as a millwright I had to tungsten carbide hard face augers for a lime injector in a rock kiln.

The trick was to preheat the whole piece and not let it cool down as you worked the rod.

I used a #12 oxygen acetylene brazing tip to do this.

As Marty suggested a non heat sink fixture would keep the temps at a even state as you worked on the piece.

Try using a ceramic slip to hold the blades instead of the Cerro.

This is how thy cast the props.

What's a ceramic slip?

Actually the Cerro is melted away leaving just the 3 scew tips/side holding the blades in place so I don't think there's much heat lost to them.

The post is a different story tho...

It is a mix like cement that when it dries it hardens.

You will have to use the slip after the milling and the blades are re-aliened.

This will keep the thin blades from over heating as you braze.

If you look at the failure. the braze stuck to the blades good. But it did not stick to the hub. the difference in temps of the two pieces is the reason for this.

That rod for the hub will pull the heat out of the hub quick. That is probably why the braze did not stick to the hub.

If you Tin the pieces first make sure you clean off the old flux before you put the two pieces together and re- braze.

 

[Tim Kish]

We use Handy &Harman 505 Braze, 28% Zinc.

660°C melt/705°C flow

I believe this is just a good all around Industrial solder that we use for a number of different applications .

I can bring some to our November meeting if you want to try it.

Tim

 

[Terry Keeley]

It is a mix like cement that when it dries it hardens.


You will have to use the slip after the milling and the blades are re-aliened.

This will keep the thin blades from over heating as you braze.

If you look at the failure. the braze stuck to the blades good. But it did not stick to the hub. the difference in temps of the two pieces is the reason for this.

That rod for the hub will pull the heat out of the hub quick. That is probably why the braze did not stick to the hub.

If you Tin the pieces first make sure you clean off the old flux before you put the two pieces together and re- braze.

Got it, thanks. Think I'll try to put the parts together hot so the braze flows together, then add a fillet.

We use Handy &Harman 505 Braze, 28% Zinc.

660°C melt/705°C flow

I believe this is just a good all around Industrial solder that we use for a number of different applications .

I can bring some to our November meeting if you want to try it.

Tim

Sure, that'd be great, looks like an all around good filler.

 

[Marty Davis]

Terry:

That is the area that Dee had trouble with. The hub. He used a solid carbon rod to slip the hub on and a carbon washer for the bottom so that it didn't heat sink. That took him a while to figure out and it worked out fine.

 

[dwilfong]

Terry once you get it figured out I could use a 1475 redone.
Can you move the blades in toward the the hub after you cut out the old hub?

A 1475 with the blade diameter reduced at the hub end of the blade and a little more pitch angle would be a killer prop.

 

[Terry Keeley]

Terry:

That is the area that Dee had trouble with. The hub. He used a solid carbon rod to slip the hub on and a carbon washer for the bottom so that it didn't heat sink. That took him a while to figure out and it worked out fine.

Ahh, the washer's a good idea too, thanks!

Terry once you get it figured out I could use a 1475 redone.

Can you move the blades in toward the the hub after you cut out the old hub?

A 1475 with the blade diameter reduced at the hub end of the blade and a little more pitch angle would be a killer prop.

Can't really move the blades in, the fixture has a step in the round ends to locate the blade axially.

I did all this because I hit a wall in the 115-117 mph range, the faster I turned the cut down 2175's the more they slipped. Props with more blade area don't slip as much but I can't get them to turn fast enough to make up the difference. The 2267 isn't any better as it has about the same LE pitch but just progresses a bunch more.

If you want a 1475 with more pitch and less diameter what about a 1667?

 

[Brad Christy]

Terry,

I would think a fillet chamfer on the blades would actually weaken the ass'y. In welding, the fillet chamfer is used to allow more filler mat'l contact with the two parts being mated. Instead of creating space for solder flow by removing mat'l, why not modify your fixture to allow the two blade mount towers to slide a bit. Slide them out (.010-.020") while heating and soldering, and then slide them in after the solder has flowed but is still hot, fully mating the two parts at the joint. Sounds complicated, but considering the effort you've already gone to, it's not so bad. Couple of dowel pins under each tower and slots to fit them, plus a thrust screw on either side and you're done.

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

Model Machine And Precision LLC

 

[Terry Keeley]

Terry,

I would think a fillet chamfer on the blades would actually weaken the ass'y. In welding, the fillet chamfer is used to allow more filler mat'l contact with the two parts being mated. Instead of creating space for solder flow by removing mat'l, why not modify your fixture to allow the two blade mount towers to slide a bit. Slide them out (.010-.020") while heating and soldering, and then slide them in after the solder has flowed but is still hot, fully mating the two parts at the joint. Sounds complicated, but considering the effort you've already gone to, it's not so bad. Couple of dowel pins under each tower and slots to fit them, plus a thrust screw on either side and you're done.

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

Model Machine And Precision LLC

Thanks for the suggestion but once the blades are located to the new pitch the "fingers" are locked in place and the new root angle is cut. Dowel pins below would work, but only for one set pitch angle.

Maybe a rotatable plate bolted in the center of each blade holder sliding on a dowel pin coming out of the main fixture. Rotate the main blade holder to the new pitch, tighten the rotating plate to locate the holder on a dowel pin. Tighten the main fixture, bore the hub then to solder loosen the holder and slide it out on the dowel pin.

That'd work!

 

[Brad Christy]

Terry,

I went back and looked at your pictures again. I was thinking your fixture was two towers mounted on the surface of the base plate. Recalculating...........

How about this:

Split your two blade holding "dials" into two disks each. One (outer) would be locked in the tower (after pitch is set), the other (inner) would hold the blade and also be mounted to the outer disk via at least two dowels (three would work better) and a thrusting screw in the center.

Set your pitch, bore the blade root, loosen the thrust screw and slide the inner disks out a bit (.010-.015"), torch it and get the braze flowing, tighten the thrust screw, closing the gap, let cool........

Make sense? I hope it comes across as it looks in my head. I think this could be done with the parts you've already made. This is the sort of thing I do for a living. Can you read a DWG file?

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

Model Machine And Precision LLC

 

[Terry Keeley]

Terry,

I went back and looked at your pictures again. I was thinking your fixture was two towers mounted on the surface of the base plate. Recalculating...........

How about this:

Split your two blade holding "dials" into two disks each. One (outer) would be locked in the tower (after pitch is set), the other (inner) would hold the blade and also be mounted to the outer disk via at least two dowels (three would work better) and a thrusting screw in the center.

Set your pitch, bore the blade root, loosen the thrust screw and slide the inner disks out a bit (.010-.015"), torch it and get the braze flowing, tighten the thrust screw, closing the gap, let cool........

Make sense? I hope it comes across as it looks in my head. I think this could be done with the parts you've already made. This is the sort of thing I do for a living. Can you read a DWG file?

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

Model Machine And Precision LLC

I get what you mean but think I've got a simpler solution (based on your idea) that works well with what I've got. Edited my description, see it?

I'll post some pics when the guys in the shop get it done! :lol:

Yup, I got CAD...