Why don't they make wedge bolts with long expansion clips like the 5 piece bolts have?

My understanding is that sleeve bolts such as 5 piece bolts are better in soft rock because the longer sleeve allows more surface area of the bolt to contact the rock, as opposed to wedge bolts that have a small expansion clip and thus little surface area in contact with the rock. Why don't they make wedge bolts with larger expansion clips like the sleeves found on 5 piece bolts? Wouldn't this result in a bolt that has enough surface area in contact with the rock to be good in soft rock, while at the same time having a thicker internal rod that is one of the advantages of wedge bolts? Seems like the best of both worlds. Or is there something I'm missing?

Wedge anchors designed for seismic loads will have expansion collars about double the length of your general purpose bolt. Interestingly, the narrowest point on a 3/8” seismic wedge is still approximately 5/16” diameter, which is the same as the bolt core on a stainless 3/8” Power-bolt.

C Williams wrote:

Wedge anchors designed for seismic loads will have expansion collars about double the length of your general purpose bolt. Interestingly, the narrowest point on a 3/8” seismic wedge is still approximately 5/16” diameter, which is the same as the bolt core on a stainless 3/8” Power-bolt.

Why can't they make them with the same narrowest point diameter as that of regular wedge bolts? Wouldn't that result in a best-of-both-worlds bolt?

Fixe and others make a double wedge bolt. Is that what you mean? They're obviously pricier than normal wedge bolts 

If you double the length of the clip you have to halve the angle of the cone (to keep the core diameter the same) which means the thread pulls out twice as far on tightening which nobody wants. The manufacturers aren't interested in soft rock, the bolts are made for concrete of known strength and they offer other solutions for softer materials like undercut bolts.

The double-clip bolts have actually worse pull-out strength in soft material than normal ones, you can look at the UPAT data sheet for this (they originally developed them). They are designed to reduce the problem that when you drill into concrete sometimes the aggregate shatters allowing the bolt to pull out until the clip meets good matrix material, with two clips one is certain of engaging initially. The clips themselves are so small they cut throigh sandstone easily.

Jim Titt wrote:

If you double the length of the clip you have to halve the angle of the cone (to keep the core diameter the same) which means the thread pulls out twice as far on tightening which nobody wants. The manufacturers aren't interested in soft rock, the bolts are made for concrete of known strength and they offer other solutions for softer materials like undercut bolts.

The double-clip bolts have actually worse pull-out strength in soft material than normal ones, you can look at the UPAT data sheet for this (they originally developed them). They are designed to reduce the problem that when you drill into concrete sometimes the aggregate shatters allowing the bolt to pull out until the clip meets good matrix material, with two clips one is certain of engaging initially. The clips themselves are so small they cut throigh sandstone easily.

Why would you have to halve the angle of the cone? 5 piece bolts have a long sleeve and they have a similar cone angle to that of any wedge bolt. Why couldn't you just take the nice long sleeve of a 5 piece and use that as an expansion clip for a wedge bolt without changing the cone angle?

Alex Fischer wrote:

...Why couldn't you just take the nice long sleeve of a 5 piece and use that as an expansion clip for a wedge bolt without changing the cone angle?

Seems that you are describing a type of sleeve anchor. The Fixe "Triplex" 12mm is one which is used for climbing. The Triplex has its pros and cons. The cone and threaded shaft are machined from a single piece. Other sleeve anchors, such as, the Powers "Power-Bolt" have a separate cone and use a standard Grade 5 hex head cap screw (aka: "bolt").

Fixe "Triplex" (above)

Other common examples, found at the hardware stores, are the Powers "Lok-Bolt" and ITW Red Head "Dynabolt". These are not suitable for climbing. They are probably Grade 1 or 2 steel (unmarked). Perhaps better suited for hanging brackets for potted plants on a masonry wall. Bolts for climbing are typically either Grade 5 hardened carbon steel or stainless steel.

https://www.itwredhead.com/products/expansion-anchors/dynabolt

ITW Red Head "Dynabolt (above)

Powers "Lok-Bolt"

Alex Fischer wrote:

Why would you have to halve the angle of the cone? 5 piece bolts have a long sleeve and they have a similar cone angle to that of any wedge bolt. Why couldn't you just take the nice long sleeve of a 5 piece and use that as an expansion clip for a wedge bolt without changing the cone angle?

Sleeve and wedge bolts only expand on the end anyway, the length of the sleeve is realistically irrelevant. There used to a bolt which was effectively one sleeve behind another but they were dropped a long time ago, wedge bolts work well enough.

Jim Titt wrote:

Sleeve and wedge bolts only expand on the end anyway, the length of the sleeve is realistically irrelevant. There used to a bolt which was effectively one sleeve behind another but they were dropped a long time ago, wedge bolts work well enough.

If the length of the sleeve is irrelevant, why is it that sleeve bolts are considered better in softer rock? How do sleeve bolts get better contact with the rock if the size and angle of the cone is similar with both bolt types?

ClimbBaja wrote:

Seems that you are describing a type of sleeve anchor. The Fixe "Triplex" 12mm is one which is used for climbing. The Triplex has its pros and cons. The cone and threaded shaft are machined from a single piece. Other sleeve anchors, such as, the Powers "Power-Bolt" have a separate cone and use a standard Grade 5 hex head cap screw (aka: "bolt").

I suppose what I am proposing is something like that triplex bolt, however the sleeve doesn't go all the way to the hex nut. The sleeve stops at a point where the bolt shaft becomes thicker (like what happens on with a standard wedge bolt). This would allow the threaded part of the bolt to be full thickness because it doesn't have to sit inside a sleeve, unlike a triplex bolt.

Have you seen the data….bolts are super strong enough.

Just don’t use plated jank outside. 

Alex Fischer wrote:

If the length of the sleeve is irrelevant, why is it that sleeve bolts are considered better in softer rock? How do sleeve bolts get better contact with the rock if the size and angle of the cone is similar with both bolt types?

No idea why some people consider them better, I've never seen comparison tests so have no opinion. The Euro opinion is different regarding sleeve bolts!

The problem with wedge bolts in soft rock is that when you try to tighten it down it can just start trenching through the rock.

I liked the triplex, but iirc it was kind of expensive. For soft rock the 1/2" red head dynabolt works pretty well mechanically, but the quaility/materials aren't great.

I like the 5 piece, but you have to be a bit more organized about keeping it all together.

slim wrote:

The problem with wedge bolts in soft rock is that when you try to tighten it down it can just start trenching through the rock.

I liked the triplex, but iirc it was kind of expensive. For soft rock the 1/2" red head dynabolt works pretty well mechanically, but the quaility/materials aren't great.

I like the 5 piece, but you have to be a bit more organized about keeping it all together.

Does the long sleeve of sleeve bolts like 5 piece and triplex bolts prevent the problem of trenching through the rock? If so, wouldn't a long expansion clip on a wedge bolt also solve that problem?

Alex Fischer wrote:

Does the long sleeve of sleeve bolts like 5 piece and triplex bolts prevent the problem of trenching through the rock? If so, wouldn't a long expansion clip on a wedge bolt also solve that problem?

Yes, the sleeve expands much further than wedge bolt sleeves, so it doesn't trench. I suspect it's not possible to make a wedge bolt design like you suggest, since an equivalent expansion sleeve would just crumple up as you pounded it in. Since the wedge bolt expansion sleeves need nubs to "catch" the rock as you tighten, the nubs would also catch the long sleeve as you pound it in, and the sleeve would just not be strong enough.

Here's an example of a hugely expanded 5-piece sleeve in poor rock. It was recovered intact because the bolt had been placed to close to an arete/edge, and a large section of rock fractured and broke off during removal. This was at Castlewood Canyon in Colorado a few years back. We replaced these bolts with 6" long glue-ins.

Alex Fischer wrote:

Does the long sleeve of sleeve bolts like 5 piece and triplex bolts prevent the problem of trenching through the rock? If so, wouldn't a long expansion clip on a wedge bolt also solve that problem?

This is conjecture on my part: It seems that a longer expansion clip (say 25% or 50% longer) on a wedge anchor, combined with a more gradual taper of the cone would distribute forces over a greater surface area within the matrix (rock). Reduced psi between clip and matrix would lessen the tendency to crush the matrix. So it is likely to improve the "trenching" problem to some degree. The trade-off would be more exposed threads when properly torqued. That results in a wedge anchor protruding enough to catch flesh or tear skin in the event of a fall. The length of exposed threads can be mitigated somewhat by backing off the nut a couple extra turns above flush with the nut, so that the wedge anchor sits deeper into the hole. Caution: tap very gently once the nut is above the threads; a nut should never be hammered upon. That damages the threads. 

You may have noticed that some brands/models have shorter or longer expansion clips. The ITW Read Head "TruBolt" has a relatively short expansion clip, while the Hilti KB3 and KB-TZ have longer clips. I have not measured the angle of taper on the cones, so cannot guess if there would be any difference in psi exerted upon the matrix. Perhaps someone would like to investigate that and come up with a guess as to which brand/model would be better if the quality of rock (psi strength) is less than ideal? I just keep it simple, "Don't use wedge anchors on anything but hard rock."

Hilti has an impressive variety of wedge anchors here.   hilti.com/c/CLS_FASTENER_71…

The Hilti Kwik Bolt 3 (aka" KB3) has been my preference for granite. There are some slight design advantages over other brands, and I have found their finish and quality control to be outstanding. The retail price for Hilti is significantly more expensive. Unless you find a deal on eBay or Craigslist, the cost can be prohibitive. Recently got a deal on KB-TZ which seem every bit as good, or better, than the KB3.

Alex Fischer wrote:

If the length of the sleeve is irrelevant, why is it that sleeve bolts are considered better in softer rock? How do sleeve bolts get better contact with the rock if the size and angle of the cone is similar with both bolt types?

I don't have any science to back this up but from my experience. Studs/wedge bolts rely on the rock metal interface to tighten. The rock must hold the clip on place so that the wedge can be drawn though. With sleeve bolts on the other hand the sleeve is supported by the washer/hanger/bolt head when the cone is drawn though. Notice how you can tighten a sleeve bolt without placing it, while you can't do that with a wedge bolt. I think this translates to much lower tension forces on the clip/sleeve when tightening allowing a sleeve bolt to expand before experiencing tensional forces where as a wedge bolt sees tension foreces first and then expands.

Greg Barnes wrote:

Yes, the sleeve expands much further than wedge bolt sleeves, so it doesn't trench. I suspect it's not possible to make a wedge bolt design like you suggest, since an equivalent expansion sleeve would just crumple up as you pounded it in. Since the wedge bolt expansion sleeves need nubs to "catch" the rock as you tighten, the nubs would also catch the long sleeve as you pound it in, and the sleeve would just not be strong enough.

Here's an example of a hugely expanded 5-piece sleeve in poor rock. It was recovered intact because the bolt had been placed to close to an arete/edge, and a large section of rock fractured and broke off during removal. This was at Castlewood Canyon in Colorado a few years back. We replaced these bolts with 6" long glue-ins.

Why do wedge bolt expansion clips need nubs to catch but sleeve bolt sleeves don't? What if we built a wedge bolt with a long expansion clip without nubs?

Blake M wrote:

I don't have any science to back this up but from my experience. Studs/wedge bolts rely on the rock metal interface to tighten. The rock must hold the clip on place so that the wedge can be drawn though. With sleeve bolts on the other hand the sleeve is supported by the washer/hanger/bolt head when the cone is drawn though. Notice how you can tighten a sleeve bolt without placing it, while you can't do that with a wedge bolt. I think this translates to much lower tension forces on the clip/sleeve when tightening allowing a sleeve bolt to expand before experiencing tensional forces where as a wedge bolt sees tension foreces first and then expands.

How would that affect holding power in soft rock? I don't see why the amount of tension the bolt sees when tightening is relevant; both bolts would see plenty of tension when being pulled out by a fall.

Alex Fischer wrote:

How would that affect holding power in soft rock? I don't see why the amount of tension the bolt sees when tightening is relevant; both bolts would see plenty of tension when being pulled out by a fall.

Increased axial tension would get translated into increased radial compressive force by the cone, ie increased force driving the clip into the surrounding rock. 

Alex Fischer wrote:

Why do wedge bolt expansion clips need nubs to catch but sleeve bolt sleeves don't? What if we built a wedge bolt with a long expansion clip without nubs?

Their basic design - just look at the bolts carefully. Some expansion bolts like 5-piece rely on the cone grabbing the rock, which is why you need to pound the bolt in to begin with (the end of the cone is slightly larger than the bolt hole, so it needs to be tapped/hammered in). Others like the Triplex, Dynabolt, and Lok-Bolts pictured above don't grab the rock at all until they are tightened, you can just slide them in the hole (and back out), although it depends on the hole and rock, sometimes they need light tapping.