Building a Bolt Tester Thread

Finally getting off my duff and starting work on a bolt tester.  Basic idea would be a hydraulic knockout punch inline with a through hole load cell on a fabricated standoff such as the fancy one below.  This is purely for hobby research and contributing on here so it doesn't have to be industry safe.  Anyone know of a decent source for such thing?  I've found a few in the 15k-20k lbs range but all are north of $500 bucks and frankly, all look like they are rebranded stuff from CN.  Any direct AliExpress source or equivalent?

Cheers

$3500 is too rich for my blood!

I make them, easy enough. Get a 10 or 15t hydraulic hole punch (ca $100-200 for a Chinese one). Drill the central piston completely through to take a 20mm threaded bar. Weld a loop/clevis on the end, spacer, washer on top. Drill and tap the cylinder to suit a digital pressure guage, build a three-legged stand and away you go. A 10t press gives a realistic 50/60kN, 15t one 80kN.
Using a strain guage is an expensive hassle and no real improvement unless the last 1% is of interest.
I can post some pics tomorrow.

Jim Titt wrote: I make them, easy enough. Get a 10 or 15t hydraulic hole punch (ca $100-200 for a Chinese one). Drill the central piston completely through to take a 20mm threaded bar. Weld a loop/clevis on the end, spacer, washer on top. Drill and tap the cylinder to suit a digital pressure guage, build a three-legged stand and away you go. A 10t press gives a realistic 50/60kN, 15t one 80kN.
Using a strain guage is an expensive hassle and no real improvement unless the last 1% is of interest.
I can post some pics tomorrow.

Awesome Jim as always. Thanks. 

mattm wrote: Finally getting off my duff and starting work on a bolt tester.  Basic idea would be a hydraulic knockout punch inline with a through hole load cell on a fabricated standoff such as the fancy one below.  This is purely for hobby research and contributing on here so it doesn't have to be industry safe.  Anyone know of a decent source for such thing?  I've found a few in the 15k-20k lbs range but all are north of $500 bucks and frankly, all look like they are rebranded stuff from CN.  Any direct AliExpress source or equivalent?

Cheers

$3500 is too rich for my blood!

Hi Matt,

I've used all of the Hydrajaws tensile testers for loading industrial rope access and climbing anchors. They are excellent units however expensive and not without particular problems for each model as I'll elaborate below.

A crucial point is that Hydrajaws make testers for proof loading construction fixings so not really for anchor extraction. Practically speaking this manifests itself in very short cylinder stroke lengths generally of only 1" (25mm) so for certified climbing anchors, the user has to reset the tester multiple times for extracting anything assuming that's the intention. A newer model (2050) has a 2" draw so a distinct help but most are limited below that.

Their clevis pins tend to fit through most glue-in anchor eyes but not any expansion bolt hanger as the pin is too thick. Even if the clevis pin fits, the clearance of the clevis block against the rock surface then prevents attachment...

To get round this issue, using a connector of some sort solves the problem but can create another (assuming it's strong enough)! This time it's the load bridge standoff versus leg length vs cylinder draw. The outcome of all of this is there can be insufficient space with the load bridge at maximum stand off from the rock, to still be able to link to the anchor and contract the cylinder and apply a load to extraction at full anchor embedment.

Other issues revolve around the tester load capacity so the junior model of the one pictured in your post connects easily, has good cylinder stroke but is limited to around 20kN. For proof loading that's more than sufficient but useless for extracting climbing anchors. The updated version of this model has the 2" cylinder stroke and higher rating of 50kN but that's really still too low for glue-ins. If you opt for the big daddy tester (100+kN) then you get hit by a short cylinder stroke...

The best of the models I used was the 2050 model (pictured) but the clevis block shaft is not thick enough and applying up to the max load of the tester (50kN) would easily bend the rod unless the tester is perfectly aligned over the fixing, something of a challenge when doing this on an uneven rock surface. Hence why these testers are designed for a flat concrete surface...

I asked Jim to build a custom puller for me in 2012 because of the above issues, not least that testers available at the time could n't exact any decent loading without needing it airlifted in...

Jim can easily make one to spec'. It'll rip out most fixings apart from any of his having tried! : )

Cheers

mattm wrote: Finally getting off my duff and starting work on a bolt tester.  Basic idea would be a hydraulic knockout punch inline with a through hole load cell on a fabricated standoff such as the fancy one below.  This is purely for hobby research and contributing on here so it doesn't have to be industry safe.  Anyone know of a decent source for such thing?  I've found a few in the 15k-20k lbs range but all are north of $500 bucks and frankly, all look like they are rebranded stuff from CN.  Any direct AliExpress source or equivalent?

Cheers

$3500 is too rich for my blood!

I can put you in touch with the Hydrajaws Asia distributor if you're interested as it's the rope access company I work for here in Hong Kong when they've got a gig going

As Francis says the big problems (apart from cost) are the limited stroke and capacity of the commercial testers, to rip out most bolts you need 50+kN and 5-6" stroke. The commercial testers generally only need to test the bolt not pull it and if they actually need them to come out then things get real big and expensive.

I´ve made four of these (I think) with two different models. The basis is a cheapo Chinese hole punch made for steelwork (making holes in steel shuttering) and they come in 10 and 15 ton vaiations. Like all Chinese hydraulic stuff the rating is when they don´t break, not what you can achieve, normally reckon on about 1/2 unless you weigh 100kg and jump up and down on the handle.

The pull cylinder is made for a threaded adaptor which is of no use to us so you unscrew the top cap, they aren´t very tight so an oil filter wrench or similar is ok. There´s a spring inside!
Remove the piston and drill through 20mm (it´s already bored most of the way so easy enough in a  pillar drill). The top cap you drill through 30mm or similar. Looks like this from the top;-

As the piston is lower than the cap you need an extension to the piston to get a nut on the pull rod (20mm stainless threadall), a piece of heavy wall pipe does this.



A clevis (or whatever on the bottom of the pull bar) and a nut and washer for the top. I make the nut easier to use by welding rod onto it, it´s only finger tight anyway.

Then a suitable base strong enough and high enought to get the range you want, maybe 8" or so. Mine are a ring to hold the ram (there´s a locking screw visible on the front which locates into a dimple you drill into the ram). The legs are 35mm thick-walled tube with M20 nuts welded on the bottom for the 20mm threaded rod feet (60-100mm long) so you can adjust for uneven rock. You need the tie rod running round the bottom to stop them spreading. It doesn´t look like it but the legs are actually angled slightly outwards.



Then you nee to decide how to measure the force, there´s four obvious choices. A normal S-beam strain guage, a pancake strain guage, a normal hydraulic guage or an electronic pressure guage. The first two are big, heavy, expensive and need (normally) a computer to read them out (other solutions are available). Normal hyraulic pressure guages (manometers) are cheap but hard to read with much accuracy as they are small, maybe 2kN is as good as you can get). I´ve used two different ones before now, a 200bar one and a 600bar (that´s the operating pressure) to try to get more accuracy for weaker bolts. Digital manometer are the way to go nowadays as they are much cheaper nowadays, under $100 or so. They are in reality a very small strain guage inside anyway so pretty accurate and have peak load readout, you have to make your own conversion chart from the pressure to the actual pull force but when you had the ram apart you measured the piston diameter so calculating is easy! Mine is fitted into an adaptor which goes between the quick coupler and the body of the ram using the old coupler hole BUT not all of the hole punches come with the coupler, some the hose is permanent (you can retro-fit them if desired). The adaptors themselves are really hard to find and cost a fortune though! All the later ones I´ve made I drill into the ram body and tap them 3/8"BSP or whatever suits the manometer.



The rod loop is to protect the guage when you throw it down the cliff! Directly under the ram on the base there is a loop welded on which you cant see, this is more or less at the balance point so you can hang the thing up on the cliff in position while you get it all set up.

I actually modify the pump as well, it´s ok if you are working on the ground where you can press against the rock or the ground but on the rope you are only squeezing the handle and the pump together, I weld up the original pivot holes on the handle and re-drill them to get more mechanical advantage.

To use it you hook it all up and pump away, the stroke is 25mm so BEFORE it ends you release the pressure and take up the slack with the wing nut and pump again. If you pump until the stroke ends the manometer records this as the maximum force so you have to reset each time otherwise, I´d put a red line on the tube extending the cylinder so you know when to stop.

If you use weak rubbish like a steel biner to connect to the bolt and it breaks the hydraulic shock may jam the valves in the coupler preventing you from retracting the ram, a tap on the pin in the coupler will free this off.

The whole thing weighs in about 12kg, better than my big one which goes in at 35kg!

Takes about  day to make and the whole thing looks like this (a different one).

Hi Jim,

I really like your design of the bolt tester.

I want to build my own, is a digital preassure gauge whith 400 bar enough for a 15 t hydraulic hole punch, or do i need a gauge with 600 bar?

Cheers

I'll have a look in the morning what the one I have uses. By the way I live near Austria (by Munich) so depending where you are you could drop by and see what it's like. You can mail me at sales@bolt-products.com 

It's 400bar which gives a bit over 80kN with the punch I use. It's actually quite hard to get even 400 bar especially hanging on a rope so I modify the pump as well but that you can do later if you need to.

Thanks you Jim!

I ordered all the parts already, i hope i can build my bolt tester next weekend. 80kN should be enough, i couldn't find cheap preassure gauges with a peak meassurement for more than 400bar.

I live near Graz so it's more than a 4 hour drive to Muinich, thanks for the offer!

I appreciate the advice with the modified pump!

When I'm finished with my pump i'll upload some pictures!