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Hose Length Determination Technique

TS Flightlines

Well Known Member
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WE get asked alot, 'how do I measure for hoses'? Well the simple answer is flare of one fitting to the flare of another, and allow for routing, bends, obstacles, etc. Thats the easy explanation. The more difficult explanation is how to do this. Well---in the absence of the actual hose ends and the actual hose being used, we have a tried an true inexpensive method.

We have found that this clear looking hose from a hardware store-Lowes plumbing section in my case--mimics the OD and bend radius of a firesleeved -6 and -8 hose. The pic shows 2 examples. The larger one is 5/8 OD, 3/8 ID with a 1/8 wall thickness. The smaller is 1/2 OD, 3/8 ID, with a 1/16 wall. So the idea is to put one end of the hose on one male fitting, and using some good routing, cut the hose so the other end is on the opposite fitting. Dont overbend, the clear hose isnt as stiff as a braided teflon hose, but you get the idea. (You can even install a hose end with some effort, depending on the type of stem to give you an even more accurate measurment.) Then take the hose and measure its cut length. That gets you very close to what the actual finished assembly length will be. Assembly length being the flare to flare dimension, no matter what hose ends are used. (Different manufacturers have different body to stem lengths for their own purposes, but those that meet Mil MS8005 for teflon have a min/max dimension. A certified teflon hose doesnt have to meet Mil MS8005 to be certified. For experimental use, the assemblies dont have to be certified, but should adhere to a similar spec.)

I bring all of this up because we do ALOT of custom assemblies. Sometimes we'll send the client a selection of hose ends and hose to do a mockup for accuracy, but most of the time we rely on the client to tell us what they want if its custom. In about 1/3 of the cases, we get a request to shorten the assembly to something else. Its time consuming for the builder---who wants to move to something else, or is held up waiting on the modification, and with shipping delays it becomes a headache. And if the assembly was short to begin with, then there needs to be a new assembly made that could have been done more correctly the first time. This is especially true for our international clients wanting custom creations. Imagine the delay and expense to either modify a hose, or make a new assembly and ship it overseas. Looked a UPS and FED EX rates lately?

So as a vendor, we try very hard to do things as precisely and quickly as possible. Because you the builder want to build and fly. Not mess around because of a hose issue. So with this little tibdit, we hopw to help you on your journey.

Tom
 

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Great Tip !!

Thanks Tom, that's a great tip !!!
If I knew...!!!

I did order some hoses from you and didn't want to mess up the lenghts of course. Waste of time and money if these measurements are wrong.
I used some safety wire and soft aluminum tubing to mock hose lenghts and since that was not as precise as I'd like, not wanted to end up short, I added 1/2 inch or a bit more for the longer hoses.

It all worked out in the end, there are some slightly larger radius turns in some cases but nothing critical.
With the clear tubing method, my hoses routings would be more compact and professional looking.
So for next time!!
 
At the suggestion of Scott Freeman, I want to retitle this as "Hose Length Determination Technique"; seems more appropriate. This idea was just another easy way to make determinations of 'custom' hose lengths, and not those hoses that were included in 'kits' or kit form. Those assembly lengths (at least from us anyway) were determined by either the design or by multiple beta testers. In Vans FWF kits, those original lengths were determined by Vans, for the Vans suggested engine combinations.

In alot of RVs and other experimentals, the builder may want to change, or add an optional accessory that differs from the original design. Remote coolers, flow transducers, cold air sumps, PMags, SDS/EFii injections, Andair selector valves----the list continues -- probably wasnt in the original 'stock' design that Vans (or others) created. So when something is changed, either the accessory or its location, chances are pretty good that a 'custom' hose assembly might be needed. Thus the simple 'Hose Length Determination Technique" post.

In the early days of TS Flightlines, we experimented with a 'bulk hose and fitting kit" based on the FWF packages that Vans were using at the time. My 'crazy' thought was to provide the hose, the hose ends, the firesleeve, and any accesssories to hand fabricate them. They featured reusable hose ends and teflon hose. At the suggestion of a very well known aerospace personality thats active on VAF, we shelved that idea. His comment was something like 'whats the cost difference between a fully assembled and tested hose, vs. one that he would have to do all the work and rig a pressure testing apparatus." The assemblies were actually less expensive, and saved TIME for him to do other tasks. While he enjoyed making his own assemblies, I personally think he enjoys shooting rivets more:eek:.

So on occasion for a very custom creation we may send teflon hose and the actual hose ends to allow the client to do a mockup that fits, then return that mockup to us for assembly and testing. Like the ones below for a F1 Rocket with a Continental IO550. Tanks and fuselage had offset ports, so we had to get creative in the space we had. LOL---USPS made good money.

So, while we do build alot of kits for drop in installs, we do quite alot of custom creations and welcome working with those builders that are different.

Tom

[Edit: Fixed the title for you Tom….. Iron]
 

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flare to flare?

Tom, when you say, "flare to flare", to which part of the flare do you mean? From the tip of the flare to the base of the flare (where the male fitting becomes cylindrical) is about an 1/8" for -6, more for -8. With two ends, that is a 1/4" difference.

I have found that sometimes, 1/4" actually matters to the hose routing, so it would be good to know.
 
Tom built a set of hoses for me based on this method.

I had some that had 45* or 90* ends also, but the FF kit included hose ends so I just made up dummy hoses with the clear Ace Hardware stuff and sent them in. For anything with both ends at an angle, this was a needed step to insure the ends are clocked correctly.
 
I used this technique when I built my RV. Clear vinyl tubing works great. Instead of cutting it to length, I simply marked it with a sharpie, then measured it laying flat. Clear off the mark with some acetone, then reuse as needed. No need to cut it.
 
Building fuel/oil lines

Just to be clear, I have used TS Flightlines to build hoses for me, and I intend to do it again for my current project.

BUT...

Here is another solution, although not as cheap as Lowes nylon tubing.
I purchased this kit on Amazon:
https://www.amazon.com/gp/product/B091YS7KFC/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&th=1

With these parts I intend to build all the hoses necessary for an inverted oil system. For those who are budget minded, you can actually use these parts for the final application, especially if you don't plan on using fire sleeve. (I would not recommend that however) At a minimum I would be inclined to go to a race supplier instead of using these cheaper parts if you plan to build your own.

Anyhow, from this kit, I'll make hoses that I know will fit, and then send them to TS Flightlines to duplicate. I know I'll get an exact fit and the TS hoses will be "plug and play".
 
Steve--we use the actual tip of the male adapter. Yes the distance from the tip to the base of the flare on a male -6 is about .100, but using the tip gives us a much better reference. Since the shortest hose we'll build -6 is 2.50 inches with straight and straight hose ends, YES the more precise the measurement the better the fit. For most of the assemblies we build, a difference of +-.125 isnt a big deal on a long hose. It is on a really short hose. And it varies slightly for the different size hoses.
The other thing we have to think about is how much "growth" the length will change when crimping the collar. WE spent a considerable amount of time (and some expense) to get actual growth data. So we compensate for that growth length when we do the cut length on the hose. That way when its assemblied and you want a 12 inch assembly, you'll get a 12 inch assembly +- our tollerance of about .060.

Tom
 
This is a very timely thread as I am on the brink of refitting one of my aircraft with new fuel and oil pressure sensing lines.

In the past I've had Steve make lines for my other airplane. He bent over backwards to provide not just a top-notch product but also truly "above and beyond" service. My new lines will be coming from Steve/Tom.

Given that I have existing lines (Aeroquip 303 lines that are aging out) it is my intent to measure the existing hose assemblies from the outside end of the female fitting's nut to the same point at the opposite end of the hose, thus capturing the "completed" hose length at its maximum dimension.

Tom - would you be able to comment on how this measurement technique impacts (negatively or positively) your fabrication process, please?
 
Hi Mark----the only thing that really matters is we KNOW where you took the measurements from. Flare to flare is the industry standard, but end of nut to end of nut can be easier if you remove the hoses and lay them out. Since the flare head dimension and nut is governed by a Mil Spec, assuming you are using an industry standard fitting like a MS24588 stem and a AN818 nut, all those dimensions are the same, no matter whos's hose ends you are using.
So as long as we know where are are taking your measurements, we can make the new assemblies. No problem.

Tom
 
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