Nozzle Throat Tool

[Loki Research]

Edit- The poll question at the top should read, "Which nozzle throat size ranges would you be most interested in measuring?" I forgot to click preview.

I'm in the process of getting a quote to have some tools made to accurately measure the throat sizes of nozzles and I would like to get some feedback from both commercial and research users of nozzles. They could be used to measure or gauge the size of your nozzle, the amount of slag build up on the throat after a burn, or the amount of erosion after the burn on a phenolic nozzle.

With a good set of calipers most smaller nozzles can be measured with fairly good accuracy, but I'm betting most people don't bring their $150+ calipers to the launch with them. Then there are those who don't even own a pair, so this is more of a field use item or a handy quick reference tool for fliers to have. There's nothing like guessing what nozzle is what size out in the field, and this item would solve that problem. It would simply be a 6"-8" long rod turned down to the correct diameters. It would also be made to last as long as possible with a minimal amount of wear.

The rough tentative plan is to-
1-Make 5 different size tools, each capable of measuring 12 different throat sizes in 1/64" increments, starting at size 6-17, 18-29, 30-41, 42-53 and finally 54-65.
2-The tool would be made to the tightest tolerance for the cost, within +0/-.002" or .003", all on the - side, as the + side would mean it may not fit through the throat.
3-The tools would be made from 6061-T6 aluminum and Type 3 Hardcoat anodized to sit in your range box and last forever.
4-They would be clearly marked to quickly indicate the size of each diameter on the tool.
5-These would not be made by hand. They would be made on a CNC lathe for close tolerance accuracy and consistency from piece to piece.

Although Loki Research nozzles are clearly marked what size throat they are in 1/64", graphite nozzles eventually wear and the throat opens up. One of my thoughts was to have the tools stepped half way between sizes so that customers can clearly see if there nozzle has opened up enough to consider replacing it or having it drilled out to a larger size. I'm still on the fence with this one though.

The feedback I would most like to have is-
1) What 12 size ranges would you be most interested in?
------If more than one size tool is of interest to you, please list them all in order of importance from most to least important.
2) What retail price point would you consider paying for an item such as I have described above, in each size of interest.
3) Would you have any interest in having a "half way point" between sizes?
4) Would you change or do something differently and if so, what and why?
5) If you are a user of graphite nozzles, do you see no value in such a tool? If so, why?

Please take the time to put some thought into your post before you answer and consider each step that needs to be taken to bring a product such as this to market. Please consider both your current and future use for this item. I have put a lot of thought into the new items I am designing for customers, so please put some thought into your reply's.


Thank you for your time and input.

 

[jpummil]

Scott,

Timely. I was about to purchase a set of telescoping hole gages for this purpose (not really ideal in my opinion).

I'd love to have a tool for 38mm, 54mm, and 76mm nozzles. Wile it's true that a single tool can't measure everything...I believe that select diameters represented on such a tool would be very handy for quick checks in the field to verify what nozzle you're actually about to drop in and fire.

Per tool? $10-$15?

 

[rockets4kids]

Why do you need something custom? A set of drill bits in 1/64 and/or metric will give you a really good idea of your nozzle size.

 

[3stoogesrocketry]

I would be interest in .5 to 1.00 sizes .

 

[Rocketjunkie]

I'd rather see a long cone with a diameter scale on it. Stick it in as far as it will go and read the diameter where it stops.

 

[Loki Research]

Why do you need something custom? A set of drill bits in 1/64 and/or metric will give you a really good idea of your nozzle size.

Drill bits cost a lot more, they take up a lot more space, and you may not have the need to use them for drilling if using them only for gauging a throat size. I have bits from #33 - #64, plus a few more, held in a simple wood framed holder. The whole thing weighs 19.7 pounds. These tools would take up a fraction of the space and weight, and cost much less than the price of a full set of bits since they don't need to cut or drill.

I'd rather see a long cone with a diameter scale on it. Stick it in as far as it will go and read the diameter where it stops.

I believe I understand what you are saying, and if I do, I would think that would be much harder to accurately measure and mark the critical points of interest. It may also be hard to see where exactly the cone stops in a throat with a well rounded entrance. If I had half steps between each 64th inch, that gets you to within 0.008". At that point it's either really tight, it has a bit of wiggle, or it's going up to the next size. Am I looking at your cone suggestion correctly?

 

[FequalsMA]

Scott,

I hear ya. For bigger nozzles my calipers are not long enough get down to the throat and measure. Have you looked at choke gauge measuring tools for shotguns for ideas? Some are a long graduated cone and some are a bar with shoulder steps for the different diameters. Like this https://www.csmcspecials.com/Lightweight_Aluminum_Choke_Gauge_p/t0252.htm or this https://www.csmcspecials.com/Stainless_Steel_Bore_Gauge_p/t0290.htm No moving parts. Very simple and effective.

 

[jimzcatz]

I'd rather see a long cone with a diameter scale on it. Stick it in as far as it will go and read the diameter where it stops.

Yeeeppp!!!

 

[cwbullet]

I'd rather see a long cone with a diameter scale on it. Stick it in as far as it will go and read the diameter where it stops.

This makes sense. It would be like a ring scale.

 

[blackjack2564]

AMW did this for 54 nozzles & 75's, right at the end. Don't think many folks even knew about them. I got it directly from Paul at a launch.

Made it easy to figure out which went where.

I think this is kinda what Scott is referring to..... This ones for the 54 nozzles.
Labeling it would be nice, these weren't, but it was only for the 4 in his set.
I think I paid 10 bucks for it.

It fit perfect in the throat, and you knew by the slop if you were getting wear or if it wouldn't go in, ya had slag or residue buildup.

 

[AlphaHybrids]

As previously mentioned, I use drill bits in 1/64" increments for nozzles up to 1". Anything bigger and I use a set of bore gauges.

Would it be cheaper to include with each reload a piece of properly machined plastic (I'm thinking Delrin) that is 1/2" long that could be used to ensure you have the proper nozzle?

Edward

 

[ncgardenfreaks]

Small hole calipers or guage blocks are what I normally use for measuring similar projects.

 

[Loki Research]

I think this is kinda what Scott is referring to..... This ones for the 54 nozzles.

It fit perfect in the throat, and you knew by the slop if you were getting wear or if it wouldn't go in, ya had slag or residue buildup.
https://www.rocketryforum.com/attachment.php?attachmentid=120713&stc=1&thumb=1&d=1362552271

Yep, Jim, that's what I had in mind, only with every 64th size in a given range per tool size. The main disadvantage I see with the cone is that you only get a reading at the entrance and are unable to see around the diameter to note any uneven wear, or as you mentioned Jim, whether or not there is any excess slag still present in the throat.

Most of you who have posted here I believe have the knowledge, tools, ability and sence to check your nozzle throats regularly. This tool is meant more for the new user or beginner who doesn't have the proper tools to do so and doesn't fully understand that when the throat gets to the next size, they are going to loose some performance and thrust. This would provide for an easy, quick double check of your nozzle throat before use.

I'll see if I can get a rough sketch of both a cone and cylidrical style tools for comparison. Perhaps I could have a few of both to begin with.

 

[cavecentral]

Yep, Jim, that's what I had in mind, only with every 64th size in a given range per tool size. The main disadvantage I see with the cone is that you only get a reading at the entrance and are unable to see around the diameter to note any uneven wear, or as you mentioned Jim, whether or not there is any excess slag still present in the throat.

Most of you who have posted here I believe have the knowledge, tools, ability and sence to check your nozzle throats regularly. This tool is meant more for the new user or beginner who doesn't have the proper tools to do so and doesn't fully understand that when the throat gets to the next size, they are going to loose some performance and thrust. This would provide for an easy, quick double check of your nozzle throat before use.

I'll see if I can get a rough sketch of both a cone and cylidrical style tools for comparison. Perhaps I could have a few of both to begin with.

I'm a little curious if such a tool in the bore gauge style (flat tool steel) could double as a slag remover? Squeeze it into the nozzle and twist 180 degrees? Getting the correct size into the nozzle throat is the challenge. The cylinder would need to be as long as the nozzle throat.

 

[Loki Research]

Kevin, I don't know that using this item to clean the throat would neccesarily be a good idea. My nightmare vision is of someone taping it too hard in the throat with a hammer and splitting the nozzle right in two, or getting slag stuck between the graphite and the tool and forcing it in hard enough to crack the To be honest, I have had ZERO problem with removing slag from the throats on the graphite material I am using, and hardly any trouble removing it from anywhere else. The only exception to this would be on Spitfire motors. When a motor fires, the graphite and it's pores both expand. The titanium gets down into those pours and when the whole thing cools, it shrinks. Now it's got a great hold on the graphite surface. I think you'd end up tearing up an aluminum tool trying to remove titanium slag. All the other oxide slags I've seen are not nearly this strong and probably would not pose much if any problem with Loki grade nozzles, but other more porous graphite may still present a problem with using it in such a manner.

Bottom line is, I would only market it as a measuring tool. If it is used in other ways, that will be up to the end user, but I don't want to suggest any use which may result in damaging someones nozzle.

 

[cavecentral]

Just a thought. I forgot you upgraded your graphite you where cleaning is easier. Yeah, it might work (might not), but the liability factor of the 'might not' is not worth the risk.

 

[cwbullet]

I think this is a great idea.

 

[AndyC]

Scott, it sounds like an interesting product, and would be most handy for getting the right nozzle in the field quickly. I'm guessing these will be most interesting for those that do EX. For users of commercial Loki loads, they would not need steps every 1/64", only those you currently use or are likely to use. The presence of excess wear can be detected by how loose the fit is. This could make for simpler and less expensive tools - perhaps you might have 2 versions: 1 for commercial users, and a set for EXers. For EX users, more complete sets would be useful, but I suspect many EXers have tools for measuring throats already (calipers, drills) - those that are most likely to buy these are probably tool junkies already (me), and have other ways of measuring.

Reasons I'm not more interested:
Like others, I already have a set of S&D drills I can use for checking throats and getting residue/deposits out on the rare occasions its necessary.
I also try to build motors at home before a launch, when I have more time and access to my tools; but don't bring my drills to launches. I have thought about getting a cheap pair of calipers to throw in my range box though; something like these.

That said, I would be interested in sizes for 38-98mm nozzles, if the price was near $10 each. Much more than that I would probably not buy them; if they could be bought in a complete set for $40-50 it would be best.

I'd think a key selling point would be to have them sized mostly by case size, so that all common 54mm throats are on one tool, etc.. There could be some overlap in really small or large throats. The idea being if I only used 54mm, I'd only need 1 tool. They also would need to be short enough to fit in my range box easily. To keep the cost down I would skip increments smaller than 1/64".

Other thoughts:
I agree on not using cones (like o-ring sizers) - may be hard to read unless the angle is very shallow, but then they get very long.
I understand why you might want to make them from hardcoated aluminum, but if they get expensive that way, have you thought about plastic? Like you point out, these are just for measuring, not for cleaning. Plastic will give before aluminum if the user gets too aggressive, but also will get marked up more easily so users will have to be more careful. On the plus side, they will be cheaper to make, and lighter in the range box (which already weighs too much). Would want to make them from a harder plastic for better wear - black delrin might be good.

 

[FredA]

TruCore already makes eomthing like this.....a small plastic triangle you slip down the throat to measure.
I find it just "OK" to use....since you measure just the external tip of the throat at two (four close) points.
A full diameter probe is a much better than a "blade."

Since I know own a full set of drills I just use that -- way easier and more precise.

 

[Loki Research]

I had consider making these for standard commercial sizes only, but I figured why go through all the expense and limit it to only a few sizes when other sizes might become used down the road, plus then there's the research guys.

Well to start out, I got a quote for a single tool, 6" long that will measure from a #10 to a #32. To purchase this tool as a finished machined product in small enough quantitys for me to stomach for the first go around, I would need to sell it at around $37 which makes a very slim margin after factoring in all other associated expenses.

So, considering that the smaller nozzles are easier to measure with the average set of calipers, I might take a second crack at this, only with the larger sizes in mind that are not able to be measured with the standard calipers. Maybe sizes 29-64. The price would likely be even higher though as the larger diameter material costs just a bit more.
I would like to think that the larger diameter tool would hold more value to people as large drill bits cost quite a bit. Plus, most of the drill bit bases people measure by are not quite spot on. Most of mine measure .004" under, which is ~1/3 of the way to the next size down.

That brings up another thing. Standard machining tolerances are +/-0.005" for most all shops. Again, that's about 1/3rd of 1/64", assuming the tolerance error is all on the plus or all on the minus side. So I'm trying to accurately measue nozzles in 1/64" with an overall tolerance that is 2/3rd of each step. Sure they can hold .001" If I want them to, but the cost goes right up with the tolerance.

So am I trying to fight a loosing battle? I have a fealing that the majority of people who feel these measurements are important enough to them to measure, either already have 1 or 2 other means of determining the diameter, or they would rather spend the money on a tool that is more versital. Like a drill bit that drills and can be used as a gauge, or a pair of $100+ calipers so they can also measure anything else. Am I right here?

 

[mikemech]

Telescoping and small hole gauges. Mine are by Starrett. Very accurate +/- .0001 in.

Mike

 

[bobkrech]

https://www.harborfreight.com/6-piece-technical-measuring-set-94447.html $8.99 the old way of measuring od and id.

https://www.harborfreight.com/6-piece-telescoping-gauge-set-5649.html $14.99 infinite resolution

https://www.harborfreight.com/3-piece-micrometer-set-66512.html $37.99 or less for single unit.

https://www.harborfreight.com/6-digital-caliper-with-metric-and-sae-fractional-readings-68304.html $20.99 or less

 

[Loki Research]

Thanks Mike, Bob. I haven't had the need for accurate measurment tools like this before and I'm seeing new stuff I never new about, like the telescoping hole gagues. So are the $14.99 sets from Harbor Freight as bad as their snap ring pliers? $15 is a great price if they work well, but I see pricing from $15 to $188 for complete sets. I already have a set of micrometers, so I'm half way there.

Well, I'll go back to the nozzle carriers. I was hoping I might be able to add something easy to use and useful to peoples range boxes, but I suppose it's wishful thinking.

Thank you all for your input and suggestions. I got what I was after which was feedback on whether or not it was worth it to pursue this. Maybe some day down the raod.

Thanks again everyone

 

[ClayD]

Thanks Mike, Bob. I haven't had the need for accurate measurment tools like this before and I'm seeing new stuff I never new about, like the telescoping hole gagues. So are the $14.99 sets from Harbor Freight as bad as their snap ring pliers? $15 is a great price if they work well, but I see pricing from $15 to $188 for complete sets. I already have a set of micrometers, so I'm half way there.

Well, I'll go back to the nozzle carriers. I was hoping I might be able to add something easy to use and useful to peoples range boxes, but I suppose it's wishful thinking.

Thank you all for your input and suggestions. I got what I was after which was feedback on whether or not it was worth it to pursue this. Maybe some day down the raod.

Thanks again everyone

I use harbor freight calipers for making my nozzles. ($9.99) I measure my throats with a guage identical to the second from the left in Bob's top picture when i cant measure with calipers.. Most of my nozzles are not strait cut throat, for one i dont use a drill bit to cut them, I hate finding center.

I would buy a guage for the commercial products. A tool for each case diameter would be nice. My use would be more intermittent on that end, so something like delrin would work over 6061 andodized.

 

[bobkrech]

Scott

A stepped tool isn't a bad idea but is shouldn't cost too much as there are other alternatives, and they are convenient.

Many HF tools are pretty good and a few are horrible. The telescoping gauges, digital verniers and micrometers are quite good, and IMO are just about as good as a Starret which costs an order of magnitude more. I purchased a 6" digital vernier from Northern Hydraulics 25 years ago, and it's still going strong and has better than 0.001" accuracy across its range.

On the other hand, if you look at McMaster for stepped or conical hole gauges you'll see they are between $500 to $700. (Ouch!) A nice protective nozzle carrier with central pins however might be of interest to folks with your hardware.

Sorry to be a party pooper, but don't want you spending a ton of money and have slow sales either.

Bob

 

[Loki Research]

Sorry to be a party pooper, but don't want you spending a ton of money and have slow sales either.

Not at all Bob, that's why I made the thread. I didn't want to do that either. Thank you

Clay, if it's a few throat size tool, that's something I could make easy enough on a hand lathe. I just don't have the time to spend doing it. If I had to pay someone else for the use of costly equipment, I had better make use of that time and make it the most versitile I can I figured. But small 5 size tools might be the first option I have that wins when more times becomes available to me. Thanks for the input.

 

[MCS]

Hey Bob,

Thanks for the pointer!

I went to Harbor Freight today and bought the Telescoping gauge set. It's not the highest precision measuring device I've ever seen, but it is definitely worth $12.. no question.

I noticed HF also has the $72 vacuum pump for sale again.

https://www.harborfreight.com/25-cfm-vacuum-pump-98076.html

Here's a coupon for 20% off any item at HF:



-->MCS

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