Micromax BT size
 

Couldn't find the info. Can anyone tell me what size body tube is used for a Micro Max rocket? I think it is BT3.

This should help.

I keep it on my desktop...easy to get to that way! :D

FlisKits sells a size of tubing called BT-2.5 (0.281" OD) that is minimum diameter Micromaxx tubing, and Aerospace Speciality Products (ASP) sells their own version, called T-MM tubing. BMS has a version called T2Plus. This tubing is suitable for motor mount tubes for Micromaxx motors. Both FlisKits and BMS also sell centering rings to fit this tubing into a variety of other sizes; ASP has centering rings to center their T-MM tubing inside their T-10.5 (BT-4) tubing (0.448" OD).

ASP uses T-MM for all of their Micromaxx kits, while FlisKits uses a variety of sizes, but mostly BT-3 (0.375" OD), in their MTTM kits.

Incidentally, BT-2.5/T-MM/T2Plus is also suitable for use as light- to medium-duty 1/4" launch lug material.

Mark \\.

Just to add a little to What mark posted:
Shortly after Quest intoduced the MicroMaxx line of (LPB's) Little plastic Bricks in 1999, Totally Tubular started selling a .013" wall white glasine 34" .255" ID, .281" OD tube. to match the OD of the MMX-I motors of the time. They called it T2+ as they their line of body tubes already contained a T2 size tube which by the way is a perfect size for use as a coupler and/or motor blocks in minimum diameter T2+ Micro Models. T2 tubes are .220" ID, .246" OD with a .013" wall.

Over the past couple years I've been extensivly experimenting with different size bodies for Micro models. These experiments have lead me to the use of T3 tubing for many of my recent downscale and custom Micro models. as it seems to give the best mix of allowing a slightly larger model to be built while remaining in the under 10gram empty finished vehicle weight.

I had Totally Tubular make up a batch of what we deemed T2++ tubes .290" ID, .316" OD with .013" wall that have seem some interesting use in models such as the micro flying jenny ejection motor pod and Falcon BG motor pod. to allow room for a motor mounted streamer.

FlisKITs has a complete line of Micro building parts that are second to NONE! Laser cut centering rings that are by far the best I've ever used. covering the complete range from T2+/T3 to T2+/BT5 or T5.
Exquisite Turned Balsa Micro Nosecones and Transisitions to fit almost any need along with steamer, Launch lug and fin materals.

To make a long story short, for Micro Maxx models your minimum motor diameter tube is the T2+ (.281"OD).

If your really interested in all things MicroMaxx Please come and join us over on the MicroMaxRockets Yahoo group. in our files and photos sections we have tips and ideas and hundreds of model plans for everyones use.

Thanks for all the helpful replies, I'm planing on some downscales using BT 5 and powered by MMX engines. Already had BT 3, anything wrong with using it for the the motor mount and wrapping tape around the engine or best to use the smaller tube to save on weight?

I guess you can but your really severely limiting your potential flights.
It'll take quite a few winds of tape to use the T3 as a motor mount tube.
Rememeber weight is the enemy with micro's. Your already paying a premium penelty using BT-5 body for your downscale. Mosquitos fly pretty well on micros but the more mass and area you add the worse it gets.
When looking at building micros try hard to keep everything as LIGHT and small as possible.
We ask alot from these little jewel motors when using that much frontal area and extra mass. Rolled computer paper models seem to work pretty well in BT-5 size. there are a couple folks who have done a bunch of downscales based on PNC-5V, Quark or Swift BT-5 cones with all paper construction.

What model are you looking at Down Scaling?

If you don't want to order any (and if you do, go to FlisKits - his T2.5 tubes are great), you can always roll your own with a 1/4" brass tube mandrel. I've made quite a few of these motor tubes and they hold up very well. Just use two or three layers of 20# computer paper. And for centering rings, use a couple layers of 110# cardstock (or in a pinch, about three layers of index card) - that will be plenty strong for micromaxx motors.

Greg

Probably a Der Red Max and Alpha, found some fin templates on EMRR. I have never flown any Micro Maxx rockets, have built a Little John from Flis and have a few unbuilt just haven't had the time to launch yet.

Go for the FlisKits parts - you won't be disappointed. I agree with Micromeister - you always have to keep the weight in mind when you are scratch-building for Micromaxx. BT-5 is actually pretty large for such rockets. ASP, FlisKits and Leading Edge all make kits for Micromaxx, but the only kit that I know of that uses BT-5 is the FlisKits Diminutive Deuce, and it has a 2-motor cluster. You might want to consider going down a tube size to BT-4 for your downscale.

Micromaxx motors can be deceptive, if you have ever flown with them. They have a really high thrust spike, relative to their size, right at ignition, but it tails off right away and the motor only delivers a tiny amount of thrust for the rest of its burn. What this means is that you can get a relatively large and heavy model boosted up and off the launch pad in a hurry, and get it to clear the launch rod, but the motor won't have enough power to keep such a model going in a vertical trajectory after that. (Dear Santa: please give us a Micromaxx booster motor that has that big thrust spike but very little thrust tail-off before it ignites the next stage.)

(Hey, John/Micromeister: Since Bill Stine is willing to consider making Micromaxx booster motors, I wonder if he would consider also making an upper stage Micromaxx motor with a 2 to 2.5 second delay. He might have to have it made in a slightly longer case, but that might actually be an advantage, because the longer motors wouldn't fit into single stage mounts (where they shouldn't be used), and it would be easy to visually distinguish between the regular single-stage MicromaxxII's and the long-delay MicromaxxIII's, or whatever they would be called. Just a thought...)

I am a big fan of FlisKits, and I absolutely love their Micro To The Maxx kits, but I also want to put in a good word for Aerospace Speciality Products (ASP). I have almost all of their micro kits (all except the Corporal). ASP really specializes (no pun intended) in scale kits, and their scale Micromaxx kits are just amazing. Check out the Micro WAC Corporal with Tiny Tim booster, the Micro Hawk and the Micro Jayhawk!

Mark \\.

Actually, I haven't had a lot of trouble flying BT-5 based models using micromaxx motors - they get up to 50/60 feet or so - definitely "backyard rockets" :D

I've used BT-5 and the three available plastic nose cones from Estes to micro-clone the Der Red Max, Alpha and Cherokee D (Cherokee MMX?), as well as micro-powering the Mosquito, Quark and 220 Swift. I also build a mmx based scale Tartar (the Swift nose is the right shape and is almost long enough - I used a thin wrap of paper soaked with CA to lengthen it). MMX was the only power option after installing the tail cone. I'll probably build another for peanut sport scale at our next regional this spring. (Raw Fusion included for scale.)

Greg