3D Props

[John Beardslee]

Hi Andy,

Are you sure about the 200 psi? Seems kinda low, as cast 2% BeCu is 70,000 psi and at full hard is 135,000 psi if I remember right. Have you ever used any pretemp 4142? It's actually 4140 ordnance steel but come pre heat treated to 40-45 Rc.

Thanks, John

 

[RaceMechaniX]

Hi Andy,

I am spinning around 55k RPM loaded with ~7hp. We came pretty close evening blowing the tail mid pass still yielded a 135mph pass.

http://youtu.be/9slpVEwsokw

TG

 

[Andy Brown]

Hi Andy,

Are you sure about the 200 psi? Seems kinda low, as cast 2% BeCu is 70,000 psi and at full hard is 135,000 psi if I remember right. Have you ever used any pretemp 4142? It's actually 4140 ordnance steel but come pre heat treated to 40-45 Rc.

Thanks, John

Hi John,

Yes, it is in the 195K to 200K range. Up around 46K psi it would go to about 235Kpsi.

 

[Andy Brown]

Hi Andy,

I am spinning around 55k RPM loaded with ~7hp. We came pretty close evening blowing the tail mid pass still yielded a 135mph pass.

http://youtu.be/9slpVEwsokw

TG

Tyler,

This prop would go well past 150 @ 50K rpm. Did you run over your wake on that pass?

 

[John Beardslee]

Hi Andy,

The "K" does make a difference. I don't remember the correlation between Rockwell hardness and psi. I remember the psi stuff on BeCu only because I didn't have access to a Rockwell tester for many years and only went by what the metallurgist at Brush Wellman told me. I did correlations but can't find them, packed away in the move in 2008 and still not unpacked somewhere!

Thanks, John

 

[Andy Brown]

Hi Andy,

The "K" does make a difference. I don't remember the correlation between Rockwell hardness and psi. I remember the psi stuff on BeCu only because I didn't have access to a Rockwell tester for many years and only went by what the metallurgist at Brush Wellman told me. I did correlations but can't find them, packed away in the move in 2008 and still not unpacked somewhere!

Thanks, John

It was late...sorry I missed the "K". These days all you have to do is Google Hardness vs.Strength and a chart you will find!

 

[RaceMechaniX]

Andy,

My theory is the blades start flexing very hard at the 100-120mph. At this point I am usually at full throttle and the motor/controller are pushing out their peak output. The blades flex and add more lift typically causing the tail blow. As soon as the prop unloads the RPM goes from 50k to 70-75k in short order and when it comes back down it usually throws a blade and promptly thereafter destroys the stub shaft, strut, and the rest of the driveline up to the collet.

The ABC cleaver and some of the Octura profiles work the best, but are not available in SS. I tried two propshop SS props that were not necessarily the right profile, but were in Stainless to see if they would survive. And they did. So I just need to cast good profiles in SS and/or work on a 3D prop I can CNC from billet or produce via SLA and have vacuum cast in SS or CoCr.

TG

 

[dwilfong]

let me see if I under stand every thing here?

There are 3d printers that will produce wax props that can then be cast out of different materials?

 

[mtruex]

David,

Actually a 3d printer could make the prop out of any material you choose, i know of one that does Ti, cobalt crome, alloy etc.. its crazy..

 

[Andy Brown]

David,

Actually a 3d printer could make the prop out of any material you choose, i know of one that does Ti, cobalt crome, alloy etc.. its crazy..

Exactly! High strength alloys have been in use in special 3D printers for awhile now. Us r/c boaters are still in the "dark ages" LOL

 

[Ian Inverarity]

Nice work everyone!...on all the CAD and CNC prop designs!

Here are photos of a CNC prop that I made in 2008.

Machined from 4340 prehardened to 42 RC.

Diameter- 42mm

L.E. 2.4"

T.E. 3.3"

Progression - 38%

Rake - 15%

Blade thinckness 50% out from hub-

T.E. - 0.8 mm

Mid. - 0.6 mm

L.E. - 0.2 mm

These dimensions are measured from the prop straight from the machine. No hand thinning has been done. Only hand work was to cut the L.E. back a small amount because it came off the machine at less than 0.1 mm (.004") thick.....razor thin!

I tested this prop on a .45 nitro rigger for durability. It survived the test with no change in dimensions.

Andy, did you CAD model the prop? If so, what software did you use?

 

[Andy Brown]

Nice work everyone!...on all the CAD and CNC prop designs!

Here are photos of a CNC prop that I made in 2008.

Machined from 4340 prehardened to 42 RC.

Diameter- 42mm

L.E. 2.4"

T.E. 3.3"

Progression - 38%

Rake - 15%

Blade thinckness 50% out from hub-

T.E. - 0.8 mm

Mid. - 0.6 mm

L.E. - 0.2 mm

These dimensions are measured from the prop straight from the machine. No hand thinning has been done. Only hand work was to cut the L.E. back a small amount because it came off the machine at less than 0.1 mm (.004") thick.....razor thin!

I tested this prop on a .45 nitro rigger for durability. It survived the test with no change in dimensions.

Andy, did you CAD model the prop? If so, what software did you use?

Ian, It is my own programming of the CNC. No CAD model and no prop design software.

 

[Ian Inverarity]

Interesting, thanks Andy.

 

[dwilfong]

I am talking cost effective.

Not NASSA.

How many $75 props can you sell?

 

[dwilfong]

Let me throw this out there.

Tyler said that his props are flexing and that was changing the prop so it would lift. If you know it will flex then make the prop so when loaded it is what you need at that speed and load. plan for the flex and adjust for it. kinda like a adjustable pitch blade.

When I ran my Pontiac I always looked for the cranks with the N cast in to them. Thy where a nodular iron crank. thy would flex with out breaking. When thy where cast thy would run DC current threw them. This would a line the grain as it cooled. Good stuff this nodular iron.

 

[Kevin Krogness]

What kinda ink cartridges do these 3D printers take? Love reading all this stuff you guys talk about but most of it goes over my head!!! My guess is the cost to run a 3D would be pretty high?

 

[Andy Brown]

Let me throw this out there.

Tyler said that his props are flexing and that was changing the prop so it would lift. If you know it will flex then make the prop so when loaded it is what you need at that speed and load. plan for the flex and adjust for it. kinda like a adjustable pitch blade.

When I ran my Pontiac I always looked for the cranks with the N cast in to them. Thy where a nodular iron crank. thy would flex with out breaking. When thy where cast thy would run DC current threw them. This would a line the grain as it cooled. Good stuff this nodular iron.

All of our props flex. I think Tyler means to say, they are flexing to the point of No Return!

 

[Andy Brown]

What kinda ink cartridges do these 3D printers take? Love reading all this stuff you guys talk about but most of it goes over my head!!! My guess is the cost to run a 3D would be pretty high?

Titainium ink! LOL

 

[Christian Lucas]

Hi,

this metal printer use metalpowder and with a laser the melt sheet by sheet of a layer of the Propeller , read here , where i print my propellers. http://www.eos.info/about_eos/history .

It' s like some girls do when the ad a layer of powder on the facesurface .Some have so much like a second skin over the natural skin.

Atatched a pic of a ROLLA 9x16 Propeller . The leading edge is so thin that i can bend the propellerblade there with my fingernail pressing the surface . This prop worked on a 2 liter Mercury outbord. Michael Werner destroyd it during a race when he hit a small pice of wood.

 

[John Beardslee]

Hi David,

Normally when props flex under load the flex doesn't increase pitch, it changes the rake to negative and that really increases the lift and jacks the tail big time.

Thanks, John