Rock-A-Chute Mark II Nose Cone
 

I recently designed and posted this design on Thingiverse which you can download for free and print.

This nose cone is designed to fit BT-50 tubing, but you can always upscale or downscale in your CAD or slicing software to suit your needs.

https://www.thingiverse.com/thing:4332295

Interesting. That will certainly suggest what the Leedes Sweete sharpener nose cone looks like.

Attached is a closeup (slightly out of focus) that shows the ribs are not as wide, of two different lengths, and that there are more of them. Since you've posted an image I took of G. Harry Stine's Mark II at the Museum of Flight back in 2010 on your Thingiverse page, it would make sense that another view, taken on the the same visit, would be useful....

If the sharpener pic was a little closer and more in focus and taken from a another angle it would helped to figure out exactly how to design it. I've looked online for other pictures, but they were out of their packaging and too far away and if up close they were in their packaging.

In the photo it's difficult to say what the exact dims are of any part of it. I inferred everything from knowing the OD of the airframe tubing and gave it my best shot.

I'd love to hold it in my hands and actually measure it and get some good photos of it.

I agree. That picture is lousy, and the pictures I have of another Mark II (taken at NSL 2013) don't show the ribs very well either.

I can try (if I remember) to get a better-focused picture of the one in the MoF next time I'm up there. I have a much better camera in my phone now than I did that December 2010 day when I took the pictures you have.

John Brohm, who is very detail oriented, wrote an article for a club newsletter detailing how to make the balsa Semroc reproduction nose cone that comes in the Mark II retro-retro kit look much more correct. It contains much detail about number, length and spacing, and is attached. I got it from him in another Mark II thread on here (more just below).

I've done a couple of Mark IIs this way, using 1/32nd basswood as the strips, and it is easy to overdo it. The ribs on the actual sharpener are not that prominent....

Added: Here are some pictures from a Mark II thread on here:

https://www.oldrocketforum.com/show...90&postcount=47
https://www.oldrocketforum.com/show...65&postcount=53
https://www.oldrocketforum.com/show...21&postcount=64
https://www.oldrocketforum.com/show...29&postcount=70

Heck, why not just cruise the entire thread for yourself. LOTS of pictures of both the actual crayon sharpeners and John Brohm's reproduction idea....

Gosh Bernard; that's some digging. Had entirely forgotten about that thread.

As my note in the thread says, the ridges on the actual artefact are a little more subtle than what I had reproduced on the model, so with a thinner strip stock one could arrive at an almost identical reproduction nose with some care.

The model pictured below I built and presented as a gift to Carl and Miss Sheryl, for all their help over the years. Remembered fondly, missed badly.

I have an original Lead's Crayon Sharpener so I measured the ridges.

They are 1.27mm or 0.05" wide and 0.50mm, or 0.02" high.

Very subtle ridges.

It would be a easier to see if I took it out of the package...but I do want to do that. :rolleyes:

The only place it says "leads" is on the bottom. It says, "A Leads Sweete Product".

I have one in a damaged package if that will help. I can easily take it out.

Gordy, I presume that height measurement is at the base of the sharpener, since the ridges taper down as they go towards the top.

Hopefully the OP will pop back in now that we have actual numbers for him to use to refine is 3D print model with.

Yes, that is correct. T measured the height of the ridge at the base.

They taper down to nothing towards the top at 1.15" long.

So the ridges are actually quite small.

Everything from our childhood is actually smaller then we remember. ;)

Is that 1.15 inches the long ones or the short ones? They alternate at two different lengths, 5 of each, around the circumference.

I sure get that “smaller than we remember” bit!

I'm sure both Carl and Sheryl appreciated the gesture as well as the craftsmanship that went into that model. Sure looked nice!

Thanks for the catch. I couldn't see that, mine is still in the package and I didn't think to rotate it.

That was the short ones at 1.15" , the long ones are just a scosh over 1.49" so I'm gonna say 1.5" for the long ones.

Be sure to read this thread: https://forums.rocketshoppe.com/sho...=mark+important

Also, does anyone know if the Quest Museum is still accessible anywhere? There were great photos not just of Leeds Sweete but also Sterling Atomic crayon sharpeners being used as Mark II nosecones.

Do you have a measurement on the exact height? Thanks!
-Jack

I've updated the design based on the input from those with the numbers, which helps a lot. Thanks to everyone for your help. Take a look at the design and let me know what you think. If I need to I will go back and create a third version.

That second picture on the thingiverse link looks MUCH better. I'm glad we were able to flush out some real dimensions for you.

Jack, I get 2.03" without the removable bottom that's for clean out the crayon shavings.

It is a crayon sharpener after all.

Thanks for the info!

my sharpener is in storage somewhere, but note that there is a slight "flare" at the bottom (and possibly a circumferal ridge at the very bottom, but that I'm not sure if it is part of the shell or the base.

I've got the Stine-Carlisle letters, and a couple of other documents on SoAR's links/resources page. I've got the old MMI photos scattered on my disk drive but not on the web. I don't remember what else was there.

looking at that old thread, there's a photo that shows the flare, and that the ridge is on the base.

https://forums.rocketshoppe.com/att...tachmentid=8446

This ebay seller has two of these crayon sharpeners listed currently. Here's one of them: https://www.ebay.com/itm/Vintage-Cr...AAOSwhB9ew~p 0


$30 each plus shipping. They say they have three for sale, but one of them is not the one used as a Mark II nose cone.

Not my listing nor do I know the lister.

Earl

bluegrassrocket is Rick Randol (the New Way Spacemodels fellow) - who is also here on YORF with that same handle.

Doh.... I thought that handle sounded familiar.


Earl

Earl,

Look at the Carlisle picture on that listing. You'll see that other sharpener used as a nose cone on some of the rockets in that photo. The rocket body looks identical to the Mark II, just the different sharpener on top.

Well, Land O' Goshen! I've seen that image a number of times in the past and never noticed the 'other' nose cone shape. I have one of more blunt sharpener cones still in the package, but not this alternate, more pointed one. But, I just 'solved' that issue.... ;)

Thanks for pointing that out.

Earl

The other sharpener nosecones are shown in the photos below. They were sold by the Sterling Plastics company of Union N.J. They used the same Leeds Sweete patent as the earlier sharpeners and may have acutally been manufactured by Leeds Sweete.

Photos below show the Sterling sharpeners in their most common package, then some comparison views of the Sterling and Leeds Sweete sharpeners.

Of note, for anyone who buys one of the sharpeners, the originals used a turned wooden plug as the nosecone shoulder. But today you can download one of the 3D files (Thingiverse?) to print a plastic shoulder.

And, again, really nice thread about these sharpeners is here.

Those Atomic sharpeners are great!

I never realized those other two rockets in that photo had sharpeners for nosecones either. Who can look at those Sterling sharpeners and somehow not think that those belong on top of a rocket!

Thanks Steve for posting these additional images and Scott for pointing out that there were indeed TWO different plastic sharpeners used as nose cones. As I mentioned above, I’ve seen that one classic black and white photo of Orville with the various Mark IIs many, many times and I never noticed there were two different nose cones. Just shows there are always new things to learn!

Earl

Steve, great photos and excellent information as always. I had to thin the herd a little amid this pandemic. I was furloughed and not essential. Some things have to give. Although, I like others, have much more time for rocket activities.

3D file to print Semroc MARK 11 Nose Cone ????
 

Looking for a 3D file that will print a nose cone to fit the Semroc MARK11. Anyone here know if there is one???

Thanks.

Check the first post in this thread. You can scale in your slicer to fit the Semroc tube.