NDT of thin wall tubing

[Henry BuckeldeeParticipant @henrybuckeldee88769]

[Henry BuckeldeeParticipant @henrybuckeldee88769]

Hi there, just wonder if any one can help with this one.

One of my hobbies is collecting and restoring vintage bicycles. I have a late 30's bicycle. A previous owner I assume has stuck a Reynolds 531 butted tubing on. Reynolds 531 was around then, as both plain and butted tube. But the hand built manufacturer does not list it for that model. So is it really Reynolds 531, or a heavier gauge tube.

The tubes we are looking at here are 1 1/8" to 1 1/4" od, 18-24 swg.

I have borrowed from work an ultrasonic tester with a stated lower thickness of 1.2 mm. On test samples this correctly measured a 1.2 mm wall tube, but on a 0.8 mm plate it measured 1.6 mm. Twice the thickness.

I have taken numerous measurements of the bicycle tube, and get figures from 1.1 to 2.0 mm. 1.1 mm could be correct for a heavy gauge tube. But 1.6 mm or higher is wrong. So do I divide by 2?

At the moment I am inclined to discount the measurements.

So is there a better way. I can only access down inside 1 tube about 20" long.

I have read about eddy current methods but not going to pay for the equipment for a one off.

Any suggestions while you have a cup of tea.

[SamsarandaParticipant @samsaranda]

Obviously the range of your ultrasonic thickness test equipment is for thickness of 1.2 MM or greater, you quote that the lowest thickness that it can check is 1.2 MM. If it correctly identifies a test piece of 1.2 MM but you say it records a value of 1.6 MM when checking a thickness of 0.8 MM this is probably because the test is out of its operating range. Difficult to comment further without knowing the model of test equipment that you are using but the results that you are getting could well be accurate, variables that could affect the test are what couplant are you using under the probe and is the frequency of the probe suitable for the specification of material being tested. You say that you rule out eddy current testing on grounds of cost, eddy current is suited to finding cracks or other such anomalies not usually used for thickness testing except in very specialised applications. If you want to test a specific thickness of material i.e. Thinner than the 1.2 MM that you have calibrated on then you need the appropriate equipment.

Dave (Retired NDT Technician)

[Henry BuckeldeeParticipant @henrybuckeldee88769]

Thanks Dave. Not got specific model of tester to hand at the moment. It is set up for steel, ie speed of sound in steel. I have been using vasaline and oil as a coupling. The measurements I have obtained in the range 1.6 – 2.00 mm cannot be true. I take your point about using the equipment outside of its stated range.

Does ultrasonic equipment exist for measurements below 1.2mm.

[HopperParticipant @hopper]

Is it possible to install a closely fitting sleeve of known thickness around the tubing and measure the combined thickness?

Otherwise you will have to get a bore gauge or T gauge down the hole and measure the ID and deduct it from the OD. Or a pair of double ended calipers as used by engine cyldiner head porters to measure thickness of metal between ports when grinding out to larger sizes. They are like a double ended pair of traditional slip joint calipers, shaped sort of like a figure 8 with a pivot in the centre of the 8 and a gap at top and bottom. You place the one end over the metal to be measured up inside the port and measure the gap in the other end with feelers to get your measurement. Hard to explain, but danged if I can find a picture of a set to post right now. You could easily make yoru own long, thin version to measure down inside your 20" tube.

[Clive Brown 1Participant @clivebrown1]

Don't think the sleeve idea will work. The signal will bounce off the interface, but no harm trying.

The 1.6mm false measurement might have been 2 bounces, which the machine won't know about.

[SamsarandaParticipant @samsaranda]

Henry,

couplant you are using is ok, inserting a sleeve will not work as you will get a return from the interface between inner and outer thickness, as suggested the readings you are getting I.e. double the anticipated reading you expect is almost certainly a double bounce because the calibrated range isn't suitable for the thickness of the tube. Is the purpose of the examinination to verify the integrity of the tube and determine wether there is any loss of thickness due to corrosion? If so examination of total surface area will be a mind numbing experience!

Dave

[Brian WoodParticipant @brianwood45127]

As another retired NDT man, I confirm the sleeve idea will fail, the interface signal will overwhelm any transfer of energy to the second surface.

​The harmonics are complex and can't be relied on either. I think Hopper's scheme to get an I/D measurement in a number of places to compare with the O/D may be in the end the best you can believe in.

​As a complete philistine, does the actual tube used really matter that much? Ducking down now below the parapet!

Regards
Brian

[egaParticipant @ega]

Henry Buckeldee:

I figured out that NDT is non-destructive testing but by "A previous owner I assume has stuck a Reynolds 531 butted tubing on" did you mean a transfer or a tube?

My impression is that in the classic period the Reynolds transfers were not readily available to owners; today it seems that just about anything can be sourced on the internet.

Good to hear from a cycle enthusiast. How about a picture of the machine?

[HevansccParticipant @hevanscc]

More information about the make and model of bicycle might throw further light on it. Also, is the Reynolds decal correct for the period:

**LINK**

Hywel

[MikeParticipant @mike89748]

Did the wall thickness of Reynolds 531 vary over the years? I have some short lengths in my workshop from a 1970s Raleigh, and I am sure some of it is 1 1/8. If it is helpful I can nip out later in the day and check the wall thickness, if it is helpful. Let me know.

[Neil WyattModerator @neilwyatt]

Posted by ega on 11/07/2017 11:36:05:

Henry Buckeldee:

I figured out that NDT is non-destructive testing but by "A previous owner I assume has stuck a Reynolds 531 butted tubing on" did you mean a transfer or a tube?

My impression is that in the classic period the Reynolds transfers were not readily available to owners; today it seems that just about anything can be sourced on the internet.

Good to hear from a cycle enthusiast. How about a picture of the machine?

You could buy tubes and the stickers were sent with them.

I nearly went through the process of getting replacement stickers for a bike I resprayed, but decided it wasn't worth the effort.

Lovely 24" frame, found partly buried in a farmyard and given in return for some work on another bike. Made a great 5-speed that conquered everything in its path with a wide-range rear sprocket and a much fitter version of me. I lost it when my Cortina estate was stolen with the bike in it. I got the car back but would rather have got the bike.

Can you check if it's butted by sticking a wire coathanger inside and feeling for the join?

Neil

[JasonBModerator @jasonb]

It's not a sudden joint Neil, stress risers and all that

[egaParticipant @ega]

Neil Wyatt:

Glad to know that you are also a cyclist; I think I already knew about Mike's trike, no doubt the source of the 531 offcuts!

Tony Oliver's "Touring Bikes" is very good on the subject of frame tubing generally and includes dimensioned cross-sectional drawings of the 700 and 708 tubes and profiles of single, double, triple and taper-butted tubes.

[MikeParticipant @mike89748]

Sorry, Neil – the tadpole trike is made of square tube and was bought as a flat pack. The 531 offcuts are the result of chopping up an old Raleigh lightweight touring bike frame for another project not yet begun.

[Mike PooleParticipant @mikepoole82104]

Does measuring the wall thickness prove it to be 531? Or are you trying to establish it is butted tube? If you set a telescopic type bore gauge to the end dimension you can access, would it not be noticeably slack if you push it further in by attaching it to a longer rod?

Mike

[MikeParticipant @mike89748]

If you guys will trust my old eyes reading a vernier, the wall thickness of the sample of 1970s 1 1/8 531 I have is 0.046. Don't know whether this is helpful or not…………

[JasonBModerator @jasonb]

0.046 is not far off 18g.

Assuming the OP is measuring the seat tube as that is usually the one you can get at then the wall thickness may be a fraction smaller at the top as it has probably bean reamed to get a good fit on the seatpost after soldering which may have slightly distorted the tube.

Don't know what condition a 90yr old seat tube would be in lower down, they tend to rust teh most from water being flung up by the back wheel so may mak it harder to feel any change in thickness

[Henry BuckeldeeParticipant @henrybuckeldee88769]

Thanks for your many replies. I will answer a few before the Tour de France highlights.

The ultrasonic tester I used is a Audit 110 from Baugh & Weedon calibrated in millimeters.

Reynolds 531 was announced in 1935 by Reynolds. Before that they had their HM range and A grade plain bore tube. 531 tubing is about 2 gauges thinner than plain gauge. The earliest Reynolds 531 catalogue I can find is dated 1946/7 on the Veteran Cycle Club library. This lists all the gauges for HM, A and 531.

The Reynolds 531 sticker I have is a transfer placed on the seat tube at the top. I believe originally you had to buy the tube to get a sticker. Now days you can just buy the transfer. My sticker looks like it's been there for many years but may not have been there when the bike was new. The sticker I have has been found on an authentic bike from 1938.

I am not trying to see if the tube is corroded, but just trying to see if it is Reynolds 531.

The bike is a 1939-1947 Grubb Special Tourer. Because of intervening war years it's difficult to date. Photos to follow.

Tour de France waits.

Henry

[David Standing 1Participant @davidstanding1]

Ah, Grubb!

I have four FH Grubb bikes (two complete, two frames awaiting build), but mine are modern upstarts (1950/60's).

[David Standing 1Participant @davidstanding1]

And is the sticker in period for the period per the H Lloyd site, as linked above?

Can you post a picture of the sticker?

[Neil WyattModerator @neilwyatt]

Posted by JasonB on 11/07/2017 13:58:32:

It's not a sudden joint Neil, stress risers and all that

Yep, but isn't over a fairly short distance, say 1/4 inch? You should be able to feel that?

[Neil WyattModerator @neilwyatt]

Here you go, I'm sure you could feel the change if this picture is realistic. Right click to see image full size:

[JasonBModerator @jasonb]

Neil if you went to spec savers you would see that it says 2" taper above both tapered sections

Hard to feel 6" down a seat tube with an old coat hanger

You need to remember my uncle was a frame builder and also built the bike I designed for myself

 

Edited By JasonB on 11/07/2017 19:45:22

[David Standing 1Participant @davidstanding1]

And Neil, you are going off at a bit of a tangent regarding double butted tubing.

Both Columbus and Accles & Pollock (to name just two of the better known tube producers) made double butted frame tubing in period, so whether or not it is double butted doesn't answer the question of whether or not it is Reynolds 531.

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