Totally Tubular Heavyweight BT-50

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Well-Known Member
Jan 18, 2009
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I ordered a bunch of tubes from Totally Tubular and the tubes are great, but I have a question.

One of the tubes is a heavier weight BT-50 with a metallic or mylar inner liner. I've not used this type of tube before. If I use this as a motor mount what type of glue can be used on the liner? Do I need to scuff this up (or off) with sandpaper first?

Thanks for any input.

You know I was wondering why you didn't ask me that Thursday when we met.

You will have two choices only that I can see.

1.) Just use an engine hook and nothing else (no bulkhead). It get's glued onto the outside.

2.) Use a 24mm RMS motor (rerloadables). They have a ring at the year. But, then you have to put a motor retainer at the rear so you keep your RMS case.

Sorry, Gus, I really don't think you can glue to it. Not without defeating the "heavy duty" part.

When I have used this I generally go without a motor block. If you scuff the inside slightly and use epoxy on the thrust ring, my bet is it will work just fine. On my 24mm upgrade of the Cluster Bomb I epoxied a ring in as well as used a hook, so it it's not a good example (that's what the original kid did, so I just followed suit)

You could always go with a masking tape thrust ring. This method, although crude, works perfectly well.
If you want to use a thrust block/ring you could use epoxy as stated above plus why not drill a few hole and pin it in with some hardwood dowels. 1/16" dia (or toothpicks)...drill through the tube just into the thrust ring. Epoxy the dowels and then sand the outside smooth.

If you plan on using a RMS case, be sure to check the forward end the hook. You might have to file it down for the RMS case to fit in all the way.

I have another suggestion that will probably work pretty well, as long as you are not using this foil-lined tube as a "stuffer" (the length of the tube only being 2.75" for a "D" engine or 3.75" for an "E".)

Assemble your motor mount relatively standard, except put the forward tab of the engine hook over the forward end of the engine tube, rather than the standard method of piercing the tube and inserting that forward tab of the engine hook through the tube. Secure the hook to the engine tube on the outside using heavy duty tape or a some other method. You will need to trim about 1/4" off of the thrust end of the motor tube doing this so that the engine will protrude from the rear of the tube enough for you to grab it and remove it after flight.

Anyway, after your mount is completely assembled, get a third centering ring that will fit the tube you're putting this mount in, but use one that centers a BT20 in that tube. For example: If you are going to put this mount in a BT60, this third centering ring will be a CR2060. Now, glue this centering ring into the body tube of your rocket at the location that will be right at the forward end of your engine tube. Then glue your motor mount in right up against that CR2060 (in this example.)

The third centering ring for the BT20 will be of smaller diameter than the inside of your heavy duty BT50, and if installed this way, will effectively act as a thrust ring for your motor (although this "thrust ring" will be glued to your airframe tube and not the standard method of being glued to your motor tube.)

I have attached a sketch of what I'm describing, maybe that will provide more clarity. Hope this helps!
Thanks everyone for the help. I didn't really have any major need to use the heavier weight tube, so I'm just going to use the regular tube instead.

Thanks again,