Replies to This Discussion

3D RoboticsPermalink Reply by Chris Anderson on February 28, 2008 at 1:12pm

I think that's a bit high for the MicroBlimp, but I could be wrong (I'll test it again. The much larger BlubberBot envelop could only lift 125 grams, but it doesn't have three motors off the shelf.

We've used the Blubberbot envelope and added a third motor and our own sensor and processor boards. See this video for more on how it works:

• ▶ Reply

Permalink Reply by Howard Gordon on February 28, 2008 at 1:58pm

Now I'm wondering about the Drexel calculations. My recollection is that 1 cu-ft of helium will lift 1 oz. If the MicroBlimp is a 20" diameter sphere, that works out to about 2.4 cu-ft, which would be 2.4 oz = 68 gm. Maybe the MicroBlimp diameter is more than 20" ?

• ▶ Reply

3D RoboticsPermalink Reply by Chris Anderson on February 28, 2008 at 2:44pm

No, 20" is right. Perhaps Drexel was referring to the older version, the "Tri-Turbofan", which was much bigger?

Also, note that the MicroBlimp is a flattened oval, not a sphere, so the volume is even less than that.

According to the Pantraco site, the electronics and gondola only weigh 12 grams all told. In my experience, you need to add a quarter and a dime (taped on for ballast) to that achieve neutral buoyancy, so you can probably figure out what that means for the total weight budget.

• ▶ Reply

Permalink Reply by Howard Gordon on February 28, 2008 at 2:56pm

A quarter and a dime combined weigh 8 gm.

So it sounds like I'll need a larger balloon. Are the motors on your Blubberbot substantially larger than the Plantraco motors, or do you think they would be adequate to drive a balloon of Tri-Turbofan size ?

update - I just found a Tri-Turbofan setup for $19.95
http://www.intelspy.com/skexshrareco.html

I ordered a couple of sets.

• ▶ Reply

3D RoboticsPermalink Reply by Chris Anderson on February 28, 2008 at 3:01pm

The Blubberbot motors are N20s, and are substantially larger than the Plantraco motors. I'd recommend that you get a Blubberbot and mod it with a third motor and new electronics, much as we have.

• ▶ Reply

Permalink Reply by Howard Gordon on February 29, 2008 at 1:04pm

New question - are you getting your helium from a welding supply ? If so, what size tank did you get, and what are you typically spending for the gas ? Looks like the non-refillable tanks for party balloons cost around $35 and only hold 15 cu ft. I called a welding supply shop, and they quoted me $369 for a 300 cu ft tank and $106 for the gas, but that's a bit of overkill.

By the way, I found some useful links on http://www.rcgroups.com/blimps-62/for other envelopes as well as some interesting designs. The outdoor performance of http://hyperblimp.com was quite impressive. One of the posts showed a single prop steered by servos - http://www.rcgroups.com/forums/showpost.php?p=8994104&postcount=8

Anyhow, there's a lot of food for thought.

• ▶ Reply

3D RoboticsPermalink Reply by Chris Anderson on February 29, 2008 at 1:30pm

Yes, we just use those disposable tanks you can get at Target. One tank can fill up our blimp at least twice.

Thanks for the other links!

• ▶ Reply

Permalink Reply by Kevin Brown on July 30, 2012 at 8:30pm

First version rip stop nylon with carbon fiber fame

version 2

Poly tubing and a seal-a-meal 

The base is about done I will post some more when I get them together for test flights

• ▶ Reply

Permalink Reply by Kevin Brown on July 30, 2012 at 9:02pm

You have to remember that balloon helium is a mix.... just enough helium to lift a latex balloon. The welding supply gas has more lift unless you get the balloon mix

and you should get you money back on the tank I use balloons for ham radio contest

KI4SCC

• ▶ Reply