Need to crunch some numbers.
Semroc lists their BT-5 O.D. at .543"

BMS lists their T-60 at 1.637"
Last edited by bradycros; 18th December 2011 at 09:34 PM.

Semroc lists their BT-5 O.D. at .543"

BMS lists their T-60 at 1.637"
A 'Scaleling Factor' is needed.

To get the Scaleing Factor for a upscale, the O.D. of the desired tube size (BT-60) needs to be divided by the O.D. of the original tube size (BT-5).
Last edited by bradycros; 19th December 2011 at 11:48 PM.

Need to crunch some numbers.

Semroc lists their BT-5 O.D. at .543"

BMS lists their T-60 at 1.637"

A 'Scaleling Factor' is needed.

To get the Scaleing Factor for a upscale, the desired tube size (BT-60) needs to be divided by the original tube size (BT-5).
So... lets see here...

1.637" divided by .543" = a scaleing factor of 3.0147329

Need to crunch some numbers.

Semroc lists their BT-5 O.D. at .543"

BMS lists their T-60 at 1.637"

A 'Scaleling Factor' is needed.

To get the Scaleing Factor for a upscale, the desired tube size (BT-60) needs to be divided by the original tube size (BT-5).

So... lets see here...

1.637" divided by .543" = a scaleing factor of 3.0147329

OK...

The 'Estes Body Tube/Kit Reference List v3.1' says kit #0872, found on page 6 of said list, needs two 4" lengths of BT-5.

8" times 3.0147329 (Scaleling Factor) = 24.117863"

OK...

The 'Estes Body Tube/Kit Reference List v3.1' says kit #0872, found on page 6 of said list, needs two 4" lengths of BT-5.

8" times 3.0147329 (Scaleling Factor) = 24.117863"

I am not overly concernd about several thousands of an inch on the length of a cardboard tube. Or hundreds of an inch on that same cardboard tube for that matter.

But a tenth of an inch...
Last edited by bradycros; 19th December 2011 at 05:02 PM.

OK...

The 'Estes Body Tube/Kit Reference List v3.1' says kit #0872, found on page 6 of said list, needs two 4" lengths of BT-5.

8" times 3.0147329 (Scaleling Factor) = 24.117863"

I am not overly concernd about several thousands of an inch on the length of a cardboard tube. Or hundreds of an inch on that same cardboard tube for thar matter.

But a tenth of an inch...

A tenth of an inch is 2.54 mm

That is going to be tossed along with the other .4537202 mm, dropping a total of 2.9937202 mm

24" instead of 24.117863" of BT-60 will be the body tube length.
Last edited by bradycros; 19th December 2011 at 04:09 AM.

Think of anything left out so far?
Will you be sanding the nose cone tip to make it a little blunter like the original Sparrow PNC-5A cone, or will you wait for time to blunt the tip? I've found CA-hardened balsa sands pretty well with 150 grit paper, in that it goes slowly enough I don't worry much about removing too much material.

A tenth of an inch is 2.54 mm

That is going to be tossed along with the other .4537202 mm, dropping a total of 2.9937202 mm

24" instead of 24.117863" of BT-60 will be the body tube length.
Originally Posted by Marc_G

Will you be sanding the nose cone tip to make it a little blunter like the original Sparrow PNC-5A cone, or will you wait for time to blunt the tip?

The original PNC-5A nose cone measured a 'tad' under a 4:1 ratio.

The upscaled BNC-60G4 nose cone measured a 'tad' over a 4:1 ratio.

With the body tube shortend a 'tad', the lengths of the two upscaled subassemblys work out to the desired overall length.

So... there will be no sanding of the tip to make it blunt. It's already the way I like it!
Last edited by bradycros; 19th December 2011 at 03:00 PM.

9. A brand spank'n new 1.637" X 34" tube (BT-60) is available at www.balsamachining.com for \$3.50
Last edited by bradycros; 19th December 2011 at 04:48 PM.

10. That's going to be a "sharp" looking rocket! I'm sure she will be a beauty. Those long tubes from BMS are great. Just got a few myself.

Will you be putting in a baffle?

11. Originally Posted by Marc_G

That's going to be a "sharp" looking rocket! I'm sure she will be a beauty. Those long tubes from BMS are great. Just got a few myself.

Will you be putting in a baffle?
"Sharp" looking rocket... "Point" taken!

Oh yes indeed, there definitely will be a baffle.
Last edited by bradycros; 19th December 2011 at 09:03 PM.

A brand spank'n new 1.637" X 34" tube (BT-60) is available at www.balsamachining.com for \$3.50

Measured 24" on the tube and made three tic marks around the tube, each at 24".

A brand spank'n new 1.637" X 34" tube (BT-60) is available at www.balsamachining.com for \$3.50

Measured 24" on the tube and made three tic marks around the tube, each at 24".

A piece of junk mail cardstock was used as a straight edge.
Last edited by bradycros; 19th December 2011 at 06:12 PM.

A brand spank'n new 1.637" X 34" tube (BT-60) is available at www.balsamachining.com for \$3.50

Measured 24" on the tube and made three tic marks around the tube, each at 24".

A piece of junk mail cardstock was used as a straight edge.

The junk mail cardstock was wraped snuggly around the tube, aligning the top edge of the cardstock with itself and the three tic marks.

A pencil is draged around the top of the cardstock.
Last edited by bradycros; 19th December 2011 at 09:58 PM.

15. Hmmmm ,I didn`t know they made BTs that long in that diameter .

Good to know !

Paul T

16. Originally Posted by sodmeister

Hmmmm ,I didn`t know they made BTs that long in that diameter .

Good to know !

Paul T

It is indeed a honor to provide The Great and Powerful sOdZ with this information!
Last edited by bradycros; 19th December 2011 at 07:54 PM.

A brand spank'n new 1.637" X 34" tube (BT-60) is available at www.balsamachining.com for \$3.50

Measured 24" on the tube and made three tic marks around the tube, each at 24".

A piece of junk mail cardstock was used as a straight edge.

The junk mail cardstock was wraped snuggly around the tube, aligning the top edge of the cardstock with itself and the three tic marks.

A pencil is draged around the top of the cardstock.

The junk mail cardstock is slid down, showing a straight line drawn on a curved surface.
Last edited by bradycros; 19th December 2011 at 09:58 PM.

18. Tube is cut with a knife.

You'll see the middle of the blade is resting on the tube. There's a reason the knife is in this position.

The knife is going to be PUSHED away from you. If the tip of the knife came into contact with the tube it would dig itself into the tube.

So don't do that!

By pushing the middle of the blade away from yourself a groove is made in the tube. Also you can steer the knife along the cut line much easyer. It's almost like steering a car, your hand just follows the eye, the eye follows the line...

After a couple of passes around the tube have been made, place the tip of the knife into the groove and PULL the knife towards you a couple centi meters at a time, then readjust the tubes position on whatever cutting surface your using. The tip of the knife will follow the groove that was made when the knife pushed away from you.

Use light pressure and make as many passes with the knife as it takes to seperate the tube. The results will be a clean cut.
Last edited by bradycros; 29th December 2011 at 12:31 PM.

19. Wow. Steady hand. I could never get a good result that way, so I made a jig kind of thing...

20. Originally Posted by Marc_G
Wow. Steady hand. I could never get a good result that way, so I made a jig kind of thing...
When cutting card BT (Loc etc) I leave the card wrap in place and follow the edge ,works great everytime and no need for a steady hand.

Paul T

21. Book it!!!!

The Brady Book and the Scotty Book
Last edited by Scotty Dog; 20th December 2011 at 03:09 AM.

22. Scotty attemps to enter "Bradys Long Winded School of Rocket Construction".
Last edited by bradycros; 20th December 2011 at 03:47 AM.

Tube is cut with a knife.

We have seperation.

Tube is cut with a knife.

We have seperation.

This method of cutting without a coupler or mandrel placed inside the tube creates a pressure ridge on the I.D.

Run a thumb nail along the pressure ridge to push the I.D. flat again.
Last edited by bradycros; 20th December 2011 at 12:01 PM.

25. Yup ,I still find cutting card tubes this way the simplest and neatest ,as it leaves a nice smooth ,tear free cut.

Paul t

Tube is cut with a knife.

We have seperation.

This method of cutting without a coupler or mandrel placed inside the tube creates a pressure ridge on the I.D.

Run a thumb nail along the pressure ridge to push the I.D. flat again.

If your unable to use your thumb nail as a tool, the same results can be had using the handle of the knife.

Scotty attemps to enter "Bradys Long Winded School of Rocket Construction".
Funny thing here,there is a Midvale TN.

Scotty attemps to enter "Bradys Long Winded School of Rocket Construction".
Originally Posted by Scotty Dog

Funny thing here,there is a Midvale TN.

Well yeah...

...your there trying to get in, again!
Last edited by bradycros; 20th December 2011 at 05:42 PM.

29. The ends of the tube could delaminate, so CA is going to be applied to prevent that from happening.
Last edited by bradycros; 20th December 2011 at 07:02 PM.