ILF Questions

Bob (apparently) said thicker (beefed up)limbs and longer bolts--nothing about being wider.  I see no reason why they wouldn't fit on any other riser "if" the limb bolts were longer.

Glad Bob is willing to accommodate the heavy-weight guys.  

Curious... do you guys really think any wood, or phenolic riser would be stronger and handle more stress than a CNC machined 6065 alloy riser?

[Bob Morrison]

The pocket will not have to be modified. The limb wedge will need to be thicker where the bolt goes thought the limb, built up with carbon or fiberglass to take the extra stress.

[vermonster13]

Your going to use the same thickness bolt and standard ILF fittings Bob?

[Turkeys Fear Me]

Originally posted by Jim Casto Jr:
 Curious... do you guys really think any wood, or phenolic riser would be stronger and handle more stress than a CNC machined 6065 alloy riser?

No, that's why I asked what I did.  It makes sense that the limb would be thicker and need a longer (not wider) limb bolt in order to have the proper amount of thread contact, but that is no different than a traditional takedown.  If the limb butt is thicker, the bolt would need to be longer.  That however, is a function of the limb and has nothing to do with the riser or  the ILF connection.

Hi Bob,

Good you're looking in.  So.... what's your thoughts on the strength comparison of ILF metal riser vs wood riser with bolt-down limbs?

[Bob Morrison]

Metal at 90+ #, Wood might??? work, Phenolic better than wood, Probably will work??? If I where hunting something that needs 90+ I would be shooting a Metal riser and Maple core limbs,and depending on your draw Carbon or fiberglass.

[Turkeys Fear Me]

Originally posted by Bill Carlsen:
While ILF bows are generally awesome bows, they have problems with heavier weights than 60# or so.

What problems would you run into?


 

Originally posted by Bowbldr:
Metal at 90+ #, Wood might??? work, Phenolic better than wood, Probably will work??? If I where hunting something that needs 90+ I would be shooting a Metal riser and Maple core limbs,and depending on your draw Carbon or fiberglass.

Thanks Bowbldr, that's what I would have thought.

[wingnut]

I would not hesitate to team up a heavy set of limbs with one of Bob's metal risers.  It would be a great combo that is strong and accurate too shoot.

Mike

[oxnam]

Hey Mike and Bob, if you guys want to put together a heavy weight to prove the point (not that you have any doubts), I'll gladly test it for you  

[Turkeys Fear Me]

TTT for clarification on the following:

 

Originally posted by Bill Carlsen:
While ILF bows are generally awesome bows, they have problems with heavier weights than 60# or so.

What "problems" are you referring to?

[Bob Morrison]

I'm not trying to talk for Bill but I think he was referring to the heavy limbs? They are not in the main stream of ILF shooters. You will not find them very often or maybe not at all from Korean,China etc. over 60#. They will more than likely need to be custom built or recut to fit the ILF riser.

[vermonster13]

Bob's ILF fittings and bushings are stainless steel so would hold up to the heavier weights much better than what is used by most main-stream ILF manufacturers which mainly use aluminum fittings and bushings.

I thought the fitting was simply for alignment and all the pressure was on the bolt and rocker.

[Bob Morrison]

Your right Jim. Our fitting is aluminum, the only pressure on it is sideways, and it is minimal. Pressure is downward on the riser. The fitting pretty much just lines up the limb until it is strung.

[Turkeys Fear Me]

Thanks Bowbldr and Jim.  I was under the impression the ILF fitting was primarily for alignment also, just like the pin in a normal takedown.

There seems to be quite a bit of confusion and old wives tales out there when it comes to this subject.

So would you say that the stress to the riser is really no different than that of any other takedown?

[Bob Morrison]

As I see it, the only difference is limb pressure pushing the bolt when strung. instead of the bolt holding limb down on the riser. No effect on riser either way.

[vermonster13]

I've had an ILF bushing from a major manufacturer fail on a Belcher ILF. Think you may want to use a higher grade limb bolt also and limit your adjustment range with the thicker limb bolt. Bolt strength is related to width as well as depth.

[Turkeys Fear Me]

Originally posted by Bowbldr:
As I see it, the only difference is limb pressure pushing the bolt when strung. instead of the bolt holding limb down on the riser. No effect on riser either way.

That's kind of what I thought, thanks.  Like I said before, I think there are a TON of misconceptions flying around about the ILF connection.

So are you back in the metal riser business again?  I know you said before that you were blowing them out and sticking with wood.

[Blake Dustin Adams]

As was said by Bob most of the force is on the limb bolt.  Thus it is basically the weakest link in the design.

I don't know if any of you come from a machining background as I do.  One of the things you learn is that all threads have a "Maximum Strength Depth".  This is the how deep into a thread a bolt has to go to reach its maximum holding strength.  Most nuts are usually very near or at the maximum strength depth.  Kinda surprising considering how small they look.

This is so because a threads strength is based on the stretch of the bolt or tensile strength.  So that being said it's figured that if a thread will pull out of a nut that is 1/2 deep for its maximum strength depth it will pull out of one that is 1 inch deep.  I'm not sure how much I believe this since it contacts twice the surface area, but I don't argue with the manual.

That being said the strength of a bolt lies in its diameter and its thread size.

It might surprise you just how strong some bolt are when being pulled.  Working as a machinist, working on cars and other mechanical objects most my life, and now being a helicopter mechanic I have seen a lot more bolts sheared than I have broken in any other way.

Also when I saw all that connects a 2,000 HP turbine engine to an input module is a few (3-6 depending on model) approximately 6mm bolts and a flex pack, and they fly without being replaced for hundreds of hours, it makes you a believer in high grade bolts.

Sorry for the length but it kinda seemed relivant

[Bob Morrison]

There was much more interest once a few guys got hold of our riser. So why not? They are built for me by a company that work with metal and are equipped better that I to make stuff out of metal. It is my design and with things I feel is important to a riser. The 2 generation has more improvements over Gen1 mostly, cosmetic. Changed the angle on the 17" and 19". Gen 3 will be along way off, I don't know of anything else I would change at this point. Wood is still our main seller, A warmth you can't get from metal.