BPC 19 Summary
Page 1 - 29/01/13
Reweighed slabs of metal located in test mass at 33.1kg. Frame of test mass has label 62kg net on it.
Note also has one anchor which consists of 17cm long 5cm diameter bar of unknown weight. Recorded
in BPC 17 all of this weighed 100 +/-1kg.
Set Pico Ch A load cell A range +/- 500mV, Ch B HE sensors OP Amp output range +/- 5V, Ch C Coil range
+/- 500mV, Ch D PT sensor range +/- 5V.
Note all 4 channels were always used but occasionally turned off the display of Ch B so data display of
recording may not show it. Use tool bar Views / Channels to tick all 4 channels to get full display.
We did not relocate PT sensor to a position nearer the centre of mass because of concern over time
pressures.
Cleaned PT white pipe with turps substitute which removed a little dirt but visually did not seem to
make much change. (Also had concern over leaving bits of white tissue behind - I had no bit free cloth!)
Note ali former set up with PTFE end caps providing very small clearance for white pipe to see if reduce
problem of free play of white pipe within ali former. (Compare to BPC 18 75 & 100 onwards.)
BPC 19 01 – hung test mass with gash rope, rattled mass and allowed to settle (note 2 sheets of data).
Aim to see how PT and HE reacted
BPC 19 02 – repeated 01 having stretched rope a little.
BPC 19 03 – used winch to lift test mass (hence spikes in trace)
Realised PT trace was small, checked back and noted should have set range to +/-2V so switch Pico Ch D
PT sensor range +/-2V.
BPC 19 04 – rattled and stretched test mass over 6 sheets of data, see sheet 5 shows moderate response
by HE, coil & PT.
Unclear if significant improvement with PTFE end caps in use.
BPC 19 10 – simple drop for g’ no shims. Noted wobble on coil trace through tR with period of 2 to 4ms.
Also noted “square wave” noise on PT trace when mass moving at some velocity.
Reset upper tR magnets to engage with HE sensors at tR.
BPC 19 11 – simple g’ drop. HE shows simple curve for tR as expected.
BPC 19 15 – rattled white pipe
Concern that PT may be located on low response area
BPC 19 16 - repeat 15 with PT at different heights. Is difference in peak to peak (50 mV and 25mV for
high and low signal) when rattled. These values seem low compared to BPC 18 work so sense PTFE end
caps do help.
Page 2
Turned white pipe around through 180 degrees so notches no longer visible to PT.
BPC 19 17 – simple g’ drop. See PT square wave noise after 2nd coil cross zero and there after every 2nd
coil cross zero.
Square wave appears to be linked to PT sensor passing magnet in one orientation (say S to N) rather
than magnetic field. Suggestion due to diode clipping current induced when PT passes magnet of other
orientation. Left alone.
BPC 19 20 – simple g’ drop (no shims in place)
BPC 19 21 – simple g’ drop
BPC 19 22 – simple g’ drop
BPC 19 23 – simple g’ drop
BPC 19 24 – simple g’ drop
BPC 19 25 – simple g’ drop
BPC 19 26 – simple g’ drop
BPC 19 27 – simple g’ drop
BPC 19 28 – simple g’ drop
Noticed some build up of noise on PT trace – concern may be due to very damp conditions within
garage. (Post analysis indicates BPC 19 04 noise 3mV, similar on BPC 19 28.)
BPC 19 29 – simple g’ drop
Decided to not insert shims on sides of test mass to reduce rattle and do set of g’ drops due to lack of
time.
Page 3
Moved on to drop new dry Marlow 10mm rope with fig 8 knots top and bottom first at FF 1.0 then at FF
0.5 to try and get results where no knot slip takes place.
Pre drop - Overall Length (OL) 1040mm Length Between Knots (LBK) 709mm (use pins in rope to provide
marker points). Distance between shackles 60mm, bomb release base 94mm from reference point
BPC 19 30 – 1st drop (nominal FF 1.0) measured bomb release now 60mm from reference point so lifted
bomb release 35mm upward, hence shackles were at same level at time of release of test mass, so was
FF 1.0. OL 1185mm, LBK 732mm.
BPC 19 31 – 2nd drop FF 1.0. OL 1220mm, LBK 737mm.
Reset distance between shackles to 630mm using 585mm length of extra tape on bomb release set up.
Bomb release 85mm below reference point.
BPC 19 32 - 3rd drop measured bomb release 65mm so lifted bomb release by 20mm, hence distance
between shackles at time of release of mass was 610mm. Given Ol pre 3rd drop was 1220mm, FF =
(1220 – 610)/1220 = 0.5. OL 1225mm, LBK 740mm
BPC 19 33 – 4th drop same distance between shackles, OL 1225mm, LBK 740mm.
BPC 19 34 – 5th drop same distance again OL 1227mm LBK 740mm
BPC 19 35 – 6th drop same distance again OL 1230mm, LBK 743mm/
Page 4
Processed two samples of rope from LTRT, see LTRT sheets for samples 4B and 3C for detail
BPC 19 41 to 49 sample 4B. Note drop 48 sheath broke and full break on 49.
BPC 19 51 to 59 sample 3C. Note sheath broke on drop 58 and full break on 59.
Page 5 - 30/01/13
Y hang work
Dummy run on Mammut 10.5mm used rope (ex CPC) tied with fig 8 on bight (bunny ears)
BPC 19 70 - 1st drop. Data seems sensible
Move to new dry Marlow 9mm rope. Set up is Y hang knot at bottom notionally upside down, with
common fig 8 knot used at top.
Measure distances of various sections of rope A “notional” overall length (between top shackle and
middle anchor point on mass) B top loop length (so loop circumference is at least 2 times length), C
lower left hand loop length, D lower right hand loop length E length between knots. Data recorded in
BPC 19 #0.xlsx file together with peak force and other details.
1st Y hang knot – figure 8 on bight (bunny ears) BPC 19 8# series
BPC 19 81 - 1st drop
BPC 19 82 - 2nd drop
BPC 19 83 - 3rd drop
BPC 19 84 - 4th drop
BPC 19 85 - 5th drop broke top figure 8
Page 6
2nd Y hang knot - Fusion knot BPC 19 9# series
BPC 19 91 - 1st drop
BPC 19 92 - 2nd drop
BPC 19 93 – 3rd drop
BPC 19 94 – 4th drop
BPC 19 95 – 5th drop broke in fusion knot
Deduce from movement of black marks made on rope that rope is moving from active side loop into
active rope between top and bottom. Note also loop sizes varied over set of drops.
Page 7
3rd Y hang knot – Double Bowline on Bight BPC 19 10# series
BPC 19 101 – 1st drop
BPC 19 102 – 2nd drop
BPC 19 103 – 3rd drop
BPC 19 104 – 4th drop
BPC 19 105 – 5th drop
BPC 19 106 – 6th drop
BPC 19 107 – 7th drop
BPC 19 108 – 8th drop
BPC 19 109 – 9th drop broke top fig 8
Page 8
4th Y hang knot – Standard Bowline on Bight BPC 19 11# series
BPC 19 111 – 1st drop
BPC 19 112 – 2nd drop
BPC 19 113 – 3rd drop
BPC 19 114 – 4thd rope broke in 2nd glazed section of rope leaving knot
Consider that for fusion and bowline on bight knots, slip through loop into rope between top and
bottom knots causes the differential change in loop lengths.
Page 9
Comparison knot for Y hang work – figure of 8 on the bight knots at each end BPC 19 12# series
BPC 19 121 – 1st drop
BPC 19 122 – 2nd drop
BPC 19 123 – 3rd drop broke at bottom knot
Insufficient rope left to do alpine butterfly option for Y hang
Page 10
Agree try testing loops of double bowline on the bight and fusion knot. Naming convention - The rope
from the active end enters into the Y hang knot and then forms a loop, hereinafter names the “Active
Side” loop. The rope then passes back into the knot and then forms the second loop, hereinafter named
the “Inactive Side” loop, before passing yet again into the knot and coming out as the inactive end of the
rope. Used a well used 10.5mm Type A SRT rope of some 7 years age was used for these tests. This
rope was difficult to bend and thus did not make “tight” knots when dressed. Set up by tie knot with
aprox 100cm long loops, dress knot and then pre load knot at 82kg hanging from loops with other end
held in jumar from top of rig. Then place selected loop on rig and the knot located so as to be
approximately halfway between top and bottom. The loop was then pre loaded at 100kg and loop
length measured. Marks were made at the knot so as to be able to measure rope slip into loop. The
test mass was then raised up to a location equivalent to a Fall Factor 1.0 and released. The increase in
rope circumference within the loop was measured. A fresh sample was used for each loop of each knot.
Double Bowline on Bight active side loop. Pre drop loop OL under 100kg 1000mm
BPC 19 131 – 1st drop OL 1090mm so rope extension is (1090 – 1000) * 2 = 180mm. Marks on rope
show knot released 120mm into loop so 60mm due to rope stretch.
BPC 19 132 – 2nd drop OL 1100mm.
Double Bowline on Bight inactive side loop. Pre drop loop OL under 100kg 1035mm
BPC 19 135 – 1st drop OL 1140mm gives 210mm extenson. Marks on rope show knot released 150mm
into loop so 60mm due to rope stretch.
Page 11
Fusion active side loop Pre drop loop OL under 100kg 1040mm
BPC 19 140 – 1st drop OL 1185mm gives 290mm extension. Marks on rope show knot released 200mm
from within knot and 30mm from active side, 230m in all so 60mm due to rope stretch.
Fusion inactive side loop Pre drop loop OL under 100kg 995mm
BPC 19 142 – 1st drop OL 1225mm gives 460mm extension. Marks on rope show knot released 360mm
from other loop and 60mm from inactive end of rope, 420mm in all, so 40mm due to rope stretch.
BPC 19 143 – 2nd drop OL 1300mm gives 75 * 2 mm extra or 610mm extension from pre drop. Marks on
rope show knot released 480mm from other loop and 81mm from inactive end of rope, 561mm in all, so
50mm due to rope stretch.
Page 12
Standard Bowline on Bight active side loop. Pre drop OL 960mm
BPC 19 145 – 1st drop OL 1085mm gives 250mm extension. Marks on ropes show 30mm from top and
190mm from bottom so discern little from other loop and 190mm from active rope so 30mm due to
rope stretch.
PT testing
Removed magnets and spacers from within white pipe and reset up on rig with nothing inside pipe. (So
no black in notches.) Notches pointing towards PT sensor. Left in top magnet to provide tR signal.
BPC 19 150 – simple g’ drop with coil and PT. No sign of square wave noise.
Relocate white pipe so notches are away from sight of PT sensor
BPC 19 151 – simple g’ drop with coil and PT. Whilst moderate amount of noise on Pt trace, no sign of
square wave noise.
Deduce PT square wave noise due to magnets.
From two sets try to identify top and bottom joins in white pipe but data unclear when revisited.
Page 13 - 31/1/13
Set up short length of Roy’s 8 by 4 by 4 magnets with spacers, see image 5620, around 30cm long and
place in bottom end of white pipe. Locate white pipe so notches away from Pt sensor.
Set up Pico Ch A load cell A range +/-500mV, ChB HE sensors range +/-5V, Ch C coil range +/-500mV and
Ch D PT sensor range +/-2V. Trigger on Ch C coil
BPC 19 160 – simple g’ drop. Shows square wave on PT.
Disconnect lead to coil on rig and also from other end.
BPC 19 161 – simple g’ drop no sign of square wave on PT so cross tlk from coil to PT.
Reconnected lead to coil but not at Pico, so coax lead lays alonf side PT coax lead.
BPC 19 162 – simple g’drop. No sign of square wave so not interference across leads.
Plug coil lead back into Pico.
BPC 19 163 – square wave back so is cross talk within Pico between Coil and PT.
Switch Ch C range to +/-100V
BPC 19 – 164 – simple g’ drop. Find coil produces 12V range (+/-6V).
Reset Ch C to +/-5V range
BPC 19 165 simple g’ drop. No square wave. But signal so small cannot really get acceptable value for
tR.
Agree to look at potential cross talk between Pico channels using Alan’s gear.
Page 14
Reset Pico Ch A load cell A range +/-500mV, Ch B HE sensors range +/-5V, Ch C Coil range +/-500mV, Ch
D PT sensor range +/-2V.
Processed two samples of rope from LTRT, see LTRT sheets for samples 1D and 2E for detail
BPC 19 171 to 79 sample 1D. Note drop 178 sheath broke and full break on 179.
BPC 19 181 to 89 sample 2E. Note sheath broke on drop 188 and full break on 189.
During work tried one person pull on rope to release test mass.
BPC 19 186 – 6th drop LTRT sample 2E noted coil trace around tR showed 2nd wave.
BPC 19 187 – 7th drop repeat with one person and found same 2nd wave more prominent.
BPC 19 188 – 8th drop used two people and found 2nd wave again even more prominent.
Recalled had not taped magnets to reduce sideways movement in pipe so taped them up. Nuts holding
magnets were tight. No expectation of vertical force which might lift magnets. Did check and found
bottom of magnets about 1cm above top of coil so is not false zero.
BPC 19 189 – 9th drop used two people and found back to normal.
End of work