Lengthening my rod.

[Senior Space Cadet]

Keep it clean, guys.
I bought an Estes launch pad with a two piece 1/4 inch rod.
I'm going to be launching some fairly long rockets.
Eventually, maybe, I'll get a rail, but until then, I'm wondering if I could lengthen the 1/4 inch rod.
I believe the Estes rod has no threaded hole on either end, so ordering a second one wouldn't help.
Do any of you know where I could order a middle section with a female on one end and a male on the other?

 

[0011001100]

https://www.mcmaster.com/metals/diameter~0-25inches/shape~rod-and-disc/stainless-steel/
Not threaded but you can get longer lengths and of stiffer material

 

[llickteig1]

Beware: long rods will create problems with rod whip.

 

[dr wogz]

Are you sure it's a 1/4" rod? the Estes 2-piece is usually a 1/8" rod, and maybe a 3/16" rod for larger rockets. 1/4" is usually when you get into MPR

Your best bet is to buy some piano wire. I've ditched the 2-piece rods that come with the Estes launch pads, as I find there is always a ridge where the two pieces come together.

Get a 1/8" dia rod x 3ft long. Get a 3/16" rod x 4ft long. Piano wire smooths out nicely, and is pretty stiff (You should be able to get it at any hobby shop or good hardware store..) I got a 6ft length of 1/4" rod from the hardware store

 

[heada]

1/8" up to 36" long, 3/16" up to 48" long and 1/4" up to 72" long. Anything longer than that and you'll get rod whip. Rails can be longer since they're much stiffer. Or you can use a higher initial thrust motor so the rod doesn't have to be as long. A long rocket doesn't have to translate into a long rod, you can have 2 lugs about a foot apart at the base of the rocket and be good with a 4 foot rod. Look at the Estes Mean Machine (full size) to see that it can work.

 

[KennB]

One of our CMASS members just got this info from Estes. They do offer a 1/4" rod. Buying a solid, single-piece rod would be the best way to get the length you want.

 

[Senior Space Cadet]

https://www.mcmaster.com/metals/diameter~0-25inches/shape~rod-and-disc/stainless-steel/
Not threaded but you can get longer lengths and of stiffer material

Thanks, looks good.

 

[Senior Space Cadet]

One of our CMASS members just got this info from Estes. They do offer a 1/4" rod. Buying a solid, single-piece rod would be the best way to get the length you want.

View attachment 424575

I got the 1/4 inch, two piece with my launch pad. I see they have a three piece which would mean being able to put the middle section in my two piece to get a longer rod. I'm sure there is a practical limit to how long you can make a 1/4" rod before bending becomes an issue.

 

[manixFan]

I bought several from Grainger. There is one near my house and I can just have it shipped there so I don't have to pay shipping costs. But as mentioned above, once you get much beyond 60" they start to whip quite a bit depending on the rocket/motor combo. A 6' SS rod from Grainger is less than $4.


Tony

https://www.grainger.com/product/GRAINGER-APPROVED-Rod-2EXC8?

 

[jrap330]

I got the 1/4 inch, two piece with my launch pad. I see they have a three piece which would mean being able to put the middle section in my two piece to get a longer rod. I'm sure there is a practical limit to how long you can make a 1/4" rod before bending becomes an issue.

As others alluded..check McMaster Carr, Hobby stores on-line and hardware stores on-line...you should fine a 1/4-1 piece cheaper than Estes. I brought my 3/16 at either a hobby store or Home Depot.....a lot cheaper than Estes 2 piece rod.....no bending/rod whip......I just wish it was 48" long.

 

[jrap330]

I bought several from Grainger. There is one near my house and I can just have it shipped there so I don't have to pay shipping costs. But as mentioned above, once you get much beyond 60" they start to whip quite a bit depending on the rocket/motor combo. A 6' SS rod from Grainger is less than $4.


Tony

https://www.grainger.com/product/GRAINGER-APPROVED-Rod-2EXC8?

Grainger usually only sells to businesses...do you have a commercial account w/them? Man that is cheap.

 

[ThirstyBarbarian]

Do any of you know where I could order a middle section with a female on one end and a male on the other?

I think that piece is technically known as "Lucky Pierre".

 

[lakeroadster]

Want to save some money? Home Depot has various diameters and lengths of steel rod. If your store doesn't have it, you can get it shipped to store, and not have to pay shipping.

1/8" dia x 48" $3.30

3/16" dia x 48" $3.98

1/4" dia x 48" $4.98

1/4" dia x 72" $5.87

3/8" dia. x 48" $7.48

3/8" dia. x 72" $10.94

I spray it down with some silicone lubricant, keeps it rust free.

 

[o1d_dude]

If you’re going to buy a new launch rod, stainless isn’t that much more expensive than rusty old metal.

 

[lakeroadster]

If you’re going to buy a new launch rod, stainless isn’t that much more expensive than rusty old metal.

And that's why you and the rest of the world are driving around in stainless cars.

 

[PatD]

And that's why you and the rest of the world are driving around in stainless cars.

Yes!!!! And it only requires 1.21 gigawatts of power!

 

[rharshberger]

iirc the cost to replace all of our clubs launch rods 1/8" thru 1/4" diameters was less than $50 US and s full 12' stick of 1/8" stainless was $12 (three years ago), we cut the 1/8" into 3' lengths, 3/16" into 3' and 4' lengths and the 1/4" in 6' lengths iirc. The stainless rods have held up really well, but the are not quite as stiff as the piano wire carbon steel rods we have.

Grainger will (at least I have locally) purchased via "cash account" but it did require a business association (I worked for the company that had an account).

 

[Cape Byron]

And that's why you and the rest of the world are driving around in stainless cars.

You have a Delorean?

 

[jrap330]

If you’re going to buy a new launch rod, stainless isn’t that much more expensive than rusty old metal.

someone on this forum wrote stainless steel rods are more flexible than non stainless, just saw it recently

 

[rharshberger]

someone on this forum wrote stainless steel rods are more flexible than non stainless, just saw it recently

Probably me, and they are slightly more flexible, however they also do not require near the care of a carbon steel rod to maintain functionality, forget to clean a carbon rod once and its going to be difficult to clean later.

 

[jrap330]

I find that after a few launches..you do need to wipe down the rod..esp 1/8 estes which some lugs fit tight. So I keep an oily rag/sock in my box and wipe it down after a few launches.

 

[Blast it Tom!]

I can't imagine stainless rods of the same diameter being noticeably less stiff than piano wire. The stiffness is not governed by the yield strength, i.e. the point at which it starts to permanently bend, but by a property called the elastic modulus - and for steels and stainless steels, these are very close to equal, no more than about a 10% difference among all varieties. Sorry for being a bit pedantic, but unless they are a little different in diameter, I'd be surprised if you could tell at all. Stainless steel is more expensive and you'll often find they are on the lower end of the tolerance., i.e. a .125" rod is actually .120" or even .115" unless you're getting precision rod, like drill rod or something. And that's a big deal - a .115" rod is only 71% as stiff as a .125" rod of the same material. (It goes by the 4th power of the diameter ratio). That you could probably notice!

So take your micrometers or calipers and make sure you're getting what you pay for!

 

[rharshberger]

I can't imagine stainless rods of the same diameter being noticeably less stiff than piano wire. The stiffness is not governed by the yield strength, i.e. the point at which it starts to permanently bend, but by a property called the elastic modulus - and for steels and stainless steels, these are very close to equal, no more than about a 10% difference among all varieties. Sorry for being a bit pedantic, but unless they are a little different in diameter, I'd be surprised if you could tell at all. Stainless steel is more expensive and you'll often find they are on the lower end of the tolerance., i.e. a .125" rod is actually .120" or even .115" unless you're getting precision rod, like drill rod or something. And that's a big deal - a .115" rod is only 71% as stiff as a .125" rod of the same material. (It goes by the 4th power of the diameter ratio). That you could probably notice!

So take your micrometers or calipers and make sure you're getting what you pay for!

Take a piece of real piano wire .125", a piece of the big box store 1/8" rod (which low carbon iirc) and a piece of 1/8" 316 stainless, cut all to 36" and mount horizontal at one end, hang a 1oz weight from the unsupported tip and the deflection will be visible and measureable. Piano aka music wire will deflect the least, its also the most expensive, hobby shops sometimes carry it in .125" diameter, and Amazon has it for $25 for three 36" section.

 

[lakeroadster]

Take a piece of real piano wire .125", a piece of the big box store 1/8" rod (which low carbon iirc) and a piece of 1/8" 316 stainless, cut all to 36" and mount horizontal at one end, hang a 1oz weight from the unsupported tip and the deflection will be visible and measureable. Piano aka music wire will deflect the least, its also the most expensive, hobby shops sometimes carry it in .125" diameter, and Amazon has it for $25 for three 36" section.

Piano wire is high carbon spring steel.... which explains why it is so stiff.

 

[manixFan]

I will admit the stainless steel rod I bought from Grainger was not as stiff as the other rod the club had. But it was a lot easier to keep clean. However I've seen stuff advertised as music wire that was just regular steel rod, so there's that.

The real answer is a rail:

https://www.amazon.com/MakerBeam-15...ial&sprefix=makerbeam+1,industrial,166&sr=1-4
and the buttons:

https://rail-buttons.com/minimicro.html

Tony

 

[rharshberger]

I will admit the stainless steel rod I bought from Grainger was not as stiff as the other rod the club had. But it was a lot easier to keep clean. However I've seen stuff advertised as music wire that was just regular steel rod, so there's that.

The real answer is a rail:

https://www.amazon.com/MakerBeam-15...ial&sprefix=makerbeam+1,industrial,166&sr=1-4
and the buttons:

https://rail-buttons.com/minimicro.html

Tony

No arguement there rails are superior to rods in my opinion, which is why the only rockets I have with lugs on them are ones built before I learned about rails.

 

[GalantVR41062]

I assembled a mpr launch pad a couple years ago. I use 1/8"(estes) 3/16" x 36"( Home Depot) and 1/4" x 72" both mild steel from Home Depot and stainless steel, low grade for sure like 409 from Grainger, my local location has a walk in "store" no account required.

The SS rod felt similar in strength to the mild steel but if I did not clean and oil the mild steel rod after every flight it would hang up and cause erratic flights from rod whip.

After the change to SS I just wipe it down before and after setting up the pad, nice and straight flights after that.

I also built a 1010 rail pad, nice for use when approaching the weight limit of a class 1 rocket or need longer length if rod exit velocity is a concern.

~John

 

[Blast it Tom!]

I'd agree with you all about rails, wish I'd known about them when I started building again last Jan.

@rharshberger

Take a piece of real piano wire .125", a piece of the big box store 1/8" rod (which low carbon iirc) and a piece of 1/8" 316 stainless, cut all to 36" and mount horizontal at one end, hang a 1oz weight from the unsupported tip and the deflection will be visible and measureable. Piano aka music wire will deflect the least, its also the most expensive, hobby shops sometimes carry it in .125" diameter, and Amazon has it for $25 for three 36" section.

I don't doubt it. But I'd suggest it is likely for the reason I stated. You can harden a steel to incredible yield strengths and it doesn't change it's stiffness one iota, just the amount of force needed to permanently bend it. Until you pass yield strength (i.e. you permanently bend it) all carbon steels are about the same, and the difference in deflections of the rods comes down to diameter, which like I said is a powerful influence. Some stainless steels are not as stiff, and yes, you could probably pick up a 10% difference with careful measurement, but I'd include a precise measure of the diameters as well. Piano wire should be very precise, i.e. if you buy .125 you get .125, not .120 or .115. I'd check the big box stuff, I've bought both as well but never made a test as you suggest. Good thought, thanks!

 

[Richard Dierking]

I recall reading a NAR paper about 15 years ago where the conclusion was that aluminum rods resulted in less rod whip. Does anyone else recall that info? Anyway, after reading the paper I switched to using aluminum rods and never had a problem.

Mini rails seem like they would work great for model rockets. I purchased some buttons from rail-buttons.com and rail material from McMaster-Carr but haven't used them yet.

You could also make the buttons from material obtained through McMaster. I make all my 1/4" and 5/16" rail buttons. Easy to replace worn parts too.

 

[Blast it Tom!]

That's interesting. For the same diameter, an aluminum rod is 1/3 as stiff as steel. So that's from a static perspective. I don't want to get into the dynamics of rod whip tonight but it seems to me that there are a number of factors: friction of the rocket's launch lugs (also a function of how well they are lined up), eccentricity of the thrust (depends on rocket diameter, etc.) inclination of the rod, mass of the rocket, amount of thrust (which sets up a bending moment via the lug friction) and so on. Like many things in our sport/hobby, we try things out and see what works, sometimes you can't put the math to everything!