BT70 Centuri Vulcan Upscale

[JAL3]

Having built 2 clones of the Centuri Vulcan and a BT60 based upscale with a 29mm motor mount, I decided that BT70 was the next logical place to try and build a member of the Vulcan family. In a bid to do something a bit different, though, I decided I wanted to use a cluster. I finally settled on a 7x18mm mount and chose to try it with the motor mount produced by Fliskits.

 

[JAL3]

The first step in construction was to select one of the BT20 motor tubes and designate it as the central motor. The single provided thrust ring was then glued flush with the end using yellow glue.

 

[JAL3]

The kit also came with 6 tube couplers. Each was marked at 1/4", the depth of the thust ring, and was inserted up to the mark in the remaining 6 motor tubes.

 

[JAL3]

The six outer tubes were then separated into three pairs. Each pair was glued together along the length of the motor tube with yellow glue. This was done on a flat surface and butted up agains a steel rule to ensure straightness.

 

[jflis]

Looking good. I will be most interested in seeing the rest of this build and how this engine mount gets integrated into the Vulcan upscale!

 

[Blades]

John, you're the man!! This one should look particularly impressive in the air. I haven't started mine yet, mostly because I haven't decided on an engine mount yet. I'll be eagerly awaiting reports on how yours does. In the interim, though, I have turned out a BT5 downscale and a BT50 upscale.

 

[JAL3]

Looking good. I will be most interested in seeing the rest of this build and how this engine mount gets integrated into the Vulcan upscale!

Thanks.

I'm still thinking about the mount. When I started, I assumed it was a "slide into the BT" like everyone else mount. I didn't realize it only goes in as far as the tube couplers.

After I get the parts printed out, I'm going to play around with them and see how it fits through the aft bulkhead. SOmething will be figured out.

 

[JAL3]

John, you're the man!! This one should look particularly impressive in the air. I haven't started mine yet, mostly because I haven't decided on an engine mount yet. I'll be eagerly awaiting reports on how yours does. In the interim, though, I have turned out a BT5 downscale and a BT50 upscale.

I was thinking last night that I needed to do some downscales.

Heck, I want to build a big family from MMX right up to 36" sonotube. My printer's not that big though.

 

[Blades]

I was thinking last night that I needed to do some downscales.

Heck, I want to build a big family from MMX right up to 36" sonotube. My printer's not that big though.

I'll be doing a MMX version to round out my family. I'll also add an upscale of the black sheep, Solomoriah's Black Vulcan (probably a BT55 upscale).
The BT5 version flies pretty well on a A3-4T, It's a little squirrely in the air, but that's kinda par for the course.

 

[JAL3]

I'll be doing a MMX version to round out my family. I'll also add an upscale of the black sheep, Solomoriah's Black Vulcan (probably a BT55 upscale).
The BT5 version flies pretty well on a A3-4T, It's a little squirrely in the air, but that's kinda par for the course.

I've got the PDFs for the blackie and will get around to that one some time.

What doe you use for paper in the MM? Is it just regular copier paper?

 

[jflis]

Thanks.

I'm still thinking about the mount. When I started, I assumed it was a "slide into the BT" like everyone else mount. I didn't realize it only goes in as far as the tube couplers.

After I get the parts printed out, I'm going to play around with them and see how it fits through the aft bulkhead. SOmething will be figured out.

Yeah, the problem there is that you can't fit 7 BT-20's inside a BT-70...

 

[rokitflite]

Yeah, the problem there is that you can't fit 7 BT-20's inside a BT-70...

OOOOOOH... I was wondering about those long couplers coming from the front of the mount! Cool solution to a simple problem .

 

[JAL3]

Yeah, the problem there is that you can't fit 7 BT-20's inside a BT-70...

My thoughts right now are to install the mount as per directions in the BT 70 and just have the cluster protruding through the bulkhead.

My alternative thought was to run the BT70 all the way through the bulkhead and then connect the mount, letting this rocket have a possible cool looking set of tailpipes.

I like the second idea but would be worried by the significant shift aft of the CG.

 

[JAL3]

After the tube pairs had dried overnight, I began the process of mounting them to the central motor tube. This was simply a matter of smearing glue on the central mount at the approximate locations where the outer tubes would contact them and then pressing the outer tubes in place. I made sure that all tubes were in agreement in terms of fore and aft and glued the pairs on. After they were in place, I gave the assembly a wrap of masking tape to keep the sides tangent while the glue set up.

 

[jflis]

OOOOOOH... I was wondering about those long couplers coming from the front of the mount! Cool solution to a simple problem .

You can thank Bob Alway for that A long time ago, on a range far, far away, Bob discovered that the width of 3 BT-20's was the same as the OD of the BT-70 (2.208" vrs 2.217", very close).

That being the case then the inside wall of the two outer BT-20's must match the ID of the BT-70... Truly an elegant solution

 

[Blades]

I've got the PDFs for the blackie and will get around to that one some time.

What doe you use for paper in the MM? Is it just regular copier paper?

I'll be using 65 lb. cardstock for the MMX Vulcan. Should work pretty well.

 

[JAL3]

I'll be using 65 lb. cardstock for the MMX Vulcan. Should work pretty well.

I guess I'll try that. I spent some time last night changing the color scheme on the shrouds of the MMX version found on the MMX Yahoo group.

Thanks.

 

[Micromeister]

The Micro Vulcan version flies very well: I believe I printed my first one on 110lb cardstock, I'll have to check.

I'd like to do a Bt-60 version sometime, do you have the shroud layouts that can be printed on a home type computer. I think I'm limited to 8.5 x 14 cardstock sheets.

 

[JAL3]

The Micro Vulcan version flies very well: I believe I printed my first one on 110lb cardstock, I'll have to check.

I'd like to do a Bt-60 version sometime, do you have the shroud layouts that can be printed on a home type computer. I think I'm limited to 8.5 x 14 cardstock sheets.

The shrouds I used on the BT60 were just upscaled by the appropriate factor and printed out on my old engineering plotter.

We started to do the same thing with the BT70 this morning and it got 90% through the first sheet when it decided to start being tempremental. Its giving "replace print head" messages and I just replaced them not too long ago.

This printer has long needed an exorcism but I can't find a language it understands. Now I'm waiting for the tech guy to call.

 

[JAL3]

I started to print out the shrouds. I made a few changes to the color scheme and sent the first page to the printer. I was quite pleased until right at the end when the blue stared fading out. I checked and the system said I was low on cyan and light cyan so replaced them both. Then the color started fading even more and I started getting "Change Printhead" errors. I just replaced the things not too long ago so I have to wait for the techie to come out and check it out.

THis has ALWAYS been the most tempramental printer!!!!

 

[JAL3]

When the glue on the cluster mount had dried, I took off the tape and inspected the result. It seemed fine to me but I wish I had a piece of BT70 lying around.

 

[JAL3]

The kit has no "centering ring" per se, instead it has 6 little pieces which, when arranged in a circle, suggest a ring with the innards cut out for the motor tubes. Each piece is fitted between a pair of the outer tubes and glued to the coupling tubes with the edges resting on the motor tubes below. They are intended to help block ejection gasses and, presumably, form an after bulkhead for the BT70 into which they will be inserted. To my delight, they fit just fine and were secured with yellow glue.

 

[JAL3]

I do have a question for Mr. Flis.

I noticed when looked at the end, there are still cavities in the interior through which ejection gasses can escape. I did not see anything in the instructions about sealing these. Did I miss something or is it not something to worry about?

 

[Peartree]

Had a similar thing with a baffle I built this fall. If you're concerned, just glom some yellow glue in there and plug it up.

 

[jflis]

I do have a question for Mr. Flis.

I noticed when looked at the end, there are still cavities in the interior through which ejection gasses can escape. I did not see anything in the instructions about sealing these. Did I miss something or is it not something to worry about?

John,

Those gaps are nothing to worry about. If you are concerned a simple drop of white glue would fill them nicely. The big gaps (when installed) are the ones blocked by those little ring segments, as you commented.

I take it the assembly of this mount went well? It was a great idea from Bob Alway and I love the way the accessory kit came out

Continued good luck on the Vulcan build!
jim

 

[JAL3]

Had a similar thing with a baffle I built this fall. If you're concerned, just glom some yellow glue in there and plug it up.

My first thought, assuming I needed to do something, was to solve the issue in the same way instructed for the Starlight Seireron 3. Some glue soaked wadding tissue was stuffed into the cavity.

What it really came down to, though, is not having a feel for the mass flow involved. I looked and saw the escape path for the gasses but really didn't know if it was significant or not. There was also the very real possibility that I missed something in the instructions. I do that too often.

 

[JAL3]

John,

Those gaps are nothing to worry about. If you are concerned a simple drop of white glue would fill them nicely. The big gaps (when installed) are the ones blocked by those little ring segments, as you commented.

I take it the assembly of this mount went well? It was a great idea from Bob Alway and I love the way the accessory kit came out

Continued good luck on the Vulcan build!
jim

As I told Peartree, I really didn't have a feel for the significance of the gaps and there was the real possibility that I missed something in the instructions.

I think it was an elegant way to fit 7 tubes in the BT70. The build was easy and I look forward to actually flying it.

 

[Handeman]

I've never build a seven motor cluster, but personally, I would not leave an opening for ejection gases on purpose unless the kit instructions specifically said to do so. I would plug any gap that I could. The glue soaked tissue is the way I would go.

 

[JAL3]

I've never build a seven motor cluster, but personally, I would not leave an opening for ejection gases on purpose unless the kit instructions specifically said to do so. I would plug any gap that I could. The glue soaked tissue is the way I would go.

That's my inclination too. THere's just a little part of me that wants to see what happens stock but I think more of me wants to rest easy that the chute comes out when its supposed to do so.

My history with Vulcans is pretty marginal to begin with.

 

[Pantherjon]

I would think that with 7 ejection charges going off that the little bit that may escape from those gaps would be pretty negligible and the chute should be deployed no problem..That is provided the nose cone isn't on terribly tight.