Rail Dawg
Always learning!!!
Am curious what other projects are potentially slated for LDRS 38?
Anyone here have some info on what's in the pipeline?
Thanks.
Chuck C.
Anyone here have some info on what's in the pipeline?
Thanks.
Chuck C.
Am curious what other projects are potentially slated for LDRS 38?
Anyone here have some info on what's in the pipeline?
Thanks.
Chuck C.
Still some work to do but with LDRS 7 weeks away there’s plenty of time to finish with time to spare.
Got one Q motor to test and one to build.
Need to get some pics posted and will do so in the next few days.
Chuck C.
Just balance it on your finger, right?(9) Verify CG with R Motor, Recovery Devices, and Electronics installed.
Just balance it on your finger, right?
Scroll down about halfway on this page: https://www.multitronix.com/transmitter.html
It will show the dimensions of the Kate transmitter and a recommended mounting scheme.
A 54mm tube is usually run right down the middle of the nosecone. It is pushed into the inside tip of the nosecone as far as it will go and then secured at the bottom by a bulkhead across the aft end of the nosecone. A short length of 54mm coupler tube should then be inserted above the transmitter to bias the transmitter back away from the tip. If the tip is metal then it would be good to bias it back at least 3-4 inches from the metal. Another 54mm coupler is then cut to length as needed to rest against the aft bulkhead and yet push the transmitter as far forward as it will go. The Kate transmitter is 11.8" long so of course the overall tube length needs to be at least that. Usually the tube is much longer than that and the coupler tubes are sized to perfectly fit the transmitter between them. The transmitter has two centering rings on it that are 4.55" apart. That is the gap size you need between the two coupler tubes that will perfectly capture the transmitter between them. I usually just cut the lower coupler tube to length in the field with a Kate transmitter installed so that it works out perfectly.
Clear as mud?
Real question time, how even do you check the CG on something this big?
Weight x Arm = Moment is a proven method to determine CG when using scales.Couldn’t you rest it on 2 scales - one on either side of the Cg? Wouldn’t the position of the Cg between the scales be the ratio of the weights?
With a few people and a sawhorse, it can be done by balancing.It will take several folks to lift and place for balance....
Yes, that is exactly what we need. Perfect!Just to verify Vern since I’m getting to the nosecone soon.
Will install a 54mm tube probably more than 18” long that will butt up against the non-metal tip of the nosecone.
There will be a bulkplate of course that will have the 54mm tube capped at the bottom. I’ll bring some 54mm coupler that we can cut to length as needed. Looks like that will cover our bases correct?
With a few people and a sawhorse, it can be done by balancing.
The rocket has a liftoff weight of 700-800 lbs . . . Trying to balance it on a horizontal 2x4 of a sawhorse would be the "Kiss of Death" !
There would either be too much force concentrated in one small area of the airframe and the rocket would "snap in two" or the 2x4 of the sawhorse would break and drop the rocket to the ground.
Dave F.
View attachment 388644
Balance it on your shoulder?
Sounds like a perfect test for the steely eyed missile men. Lol
The engineering team, whoever they are, should be abke to handle it.
Each piece of the rocket has its own weight (w) and its own CG at a location within that piece. Carefully record those weights and CGs.
When stacked together (on paper or real life), record the distance (x) of each piece's CG from the base of the rocket . Multiply each section's weight by its corresponding distance and Add them together (w1x1 + w2x2 + w3x3 + etc...)
Divide that sum by the total mass of the rocket, and the result is the CG of the whole thing (aka, the composite object)
Link below
https://hyperphysics.phy-astr.gsu.edu/hbase/cm.html
I'd find a nice tree with a sturdy low branch, hook up a come-along to the branch and either assemble the rocket on the ground or appropriate amount of bucks put sling at approximate CG and crank it up a few inches. Adjust until CG is found.
I'll add or a joist or an engine puller, anything overhead that is capable of handling the weight.
+1
how we did with a 675lb one. Used the hitch on truck to pull rocket a few inches above ground.
used 1inch TN.[4500lb rated] loop tied with bowline so it could slide into position. Simple and you KNOW exactly where CG is..no guessing with calculations.
Block & tackle would be even better.
+2 Jim
In my humble opinion this method is the absolute best way to get an accurate CG location for a project this size. It can be done safely and quickly with a little preparation.
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