Good Techie Info...
11-08-2002 | 07:40 PM
#1
Thread Starter
Boone & Crockett
Joined: Feb 2003
Posts: 12,157
Likes: 0
From: Lehigh County PA USA
Good Techie Info...
For all of you techie nuts out there I have a good, short article to share with you but first a little explanation. On another message board I frequent there was some question as to the validity of some of the statements that I posted regarding the Hoyt Razortec. In attempting to find some answers I received a very informative email from some of the engineers at Hoyt and I thought I would share it with you folks.......
"Thoughts on TEC Risers and Split Limbs
Risers
Material. 6061-T6 is the material of choice for bow risers for several reasons. First, it has very good strength properties, as has been pointed out above. Second, it has an elongation rating which allows it to inhibit stress cracking, and thus keep the riser from snapping. Third, it is commonly available as either a forging or an extrusion that makes it economical.
Advantage: Best blend of strength, weight, and availability
Design. All risers are not created equal. There are fundamental differences in the geometries used to produce risers. A bow riser functions much the same as a bridge over a river does. Its purpose is to hold the limbs in their position and not let them move. Early bridges were made using beams. These beams were often made from 2 X 10 pieces of lumber laid on end and fastened together side by side. These bridges were adequate initially, but as the weight the bridges were required to carry increased, several fundamental design flaws were exposed. First, these bridges would deflect as heavy loads were applied, creating instability at the ends. Second, these bridges had a tendency to “bounce” as they would deflect and recover when the load passed over the surface. Consequently, a new design of bridge was developed. The new bridge designs common today utilize a truss structure, which we commonly refer to as a ”bridge” geometry today. These trusses are built of multiple pieces of material braced together to form the bridge. This design provided a much stiffer member with less overall mass weight of materials. Thus the strength-to-weight ratio of these designs is far superior. As we apply this analogy to bow riser design, we note that most risers on the market are made from a slender piece of aluminum. This design, when coupled with the short, high performance limbs of today, produces a riser that flexes greatly at full draw. Most of you have shot a bow without a bow sling and had it fly out of your hand and bounce painfully on the floor. This phenomenon exists because the riser is deflecting at full draw, where the load on the riser is the greatest, and then recovering when it is shot. Your bow hand can feel the vibration resulting from this deflection and recovery process. Hoyt’s TEC risers have been designed to utilize the principles of a truss. The brace which bridges the top of the riser to the bottom of the riser across the grip area, provides an incredible amount of support to the riser. Consequently, the riser does not flex nearly as far as it would without the support. Additionally, the lack of deflection actually stops vibration at its root—deflection. Hoyt has taken a proactive approach in designing means to prevent vibration, rather than dampen vibration after it occurs. One open handed shot with a TEC bow will illustrate the difference in the amount of riser flex in these bows compared to the rest. Hoyt has done an extensive amount of testing with this design. It is by far the most superior design for risers. It is the reason why Hoyt is the only bow company who can produces cast magnesium risers which do not fail with today’s high performance limbs and cams. All of the Hoyt risers are tested in a dryfire condition which pulls an 80 lb bow to 30” of draw and then lets the string go, at full draw. Every Hoyt TEC riser on the market will survive 1,500 of these dryfires without cracking, bending, or failing in any way. Testing of other brands of product shows there is no other riser design that comes close to these benchmarks.
Advantages of TEC risers: Less shot vibration, lighter mass weight, improved overall bow balance, improved accuracy, stronger riser design, smaller grip, quieter shot, better aiming, and less hand torque.
More Riser Thoughts
Hoyt has designed all of their new TEC risers (2000, 2001, 2002, & 2003) with a Finite Element Analysis software package that allows them to perform simulations of deflection, vibration, stress, strain and other important design factors. They have spent the past three years refining designs that would optimize the factors of weight, deflection, and vibration. The designs they have produced perform very similarly in deflection, and vibration to the risers that in the past have weighed twice as much. The new 2003 bows weigh as little as 3 lb 4 oz, yet shoot like they weigh much more than that. This is due to the optimization of material in the bridge design.
Another fascinating advantage of the TEC riser design is its ability to dampen vibration. There are two sources of vibration. The riser produces vibration that is low frequency and high amplitude. The limbs produce vibration that is high frequency and low amplitude. (I learned this from Steve Sims.) His Enhancer product was developed to take out the low frequency riser vibration. The limb saver and other products were designed to take out the high frequency string and limb vibration. He told me that the Enhancer product does not work particularly well on TEC bows because they have an entirely different vibration profile than any other type of riser. This low frequency vibration does not exist in the TEC bows to the extent that it does in other bows. The high frequency vibration also dampens much quicker in the TEC risers than other risers he has tested. He felt that the TEC risers were designed extremely well from a vibration standpoint. As he worked with the Hoyt engineers to improve their bows, the only significant improvement they could make was to add the limb saver to the limb to reduce the audible noise level of the bow.
Limbs
Material. Bow limbs create many unique problems for designers. They require very stiff materials, however, these materials must be able to flex repeatedly without being damaged. Of all the materials available, none performs as well as glass. There are several different categories of glass ranging from e-glass to s-glass. Each has its own set of performance characteristics. Each is suited to a different application. Carbon is the stiffest material utilized in limb manufacturing today. However, carbon is very brittle and cannot stretch very far without breaking (engineering term is strain). This is the reason why most manufacturers put carbon in the center of their limbs close to the neutral axis, where there is less strain.
Lamination. Laminated limbs are superior to unlaminated limbs in two ways. First, materials can be layered in a manner which suits their material characteristics. Second, the limb can be contoured in a recurve fashion that makes the limb more efficient.
Advantages of laminated limbs: stores more energy, lighter mass weight, increased velocity, increased durability, and increased stability.
Design. Limbs have historically been produced as a single member with a groove cut in one end for the cam, and the other end for the limb bolt. This design produces two stress concentrations at the apex of each of these cutouts. The result is a premature failure of the limb at one of these two areas. Painstaking efforts have been made to strengthen these two weak points. Limbs have been designed with v-groove buttons, overlays, and various other strengthening mechanisms to reinforce these areas. The most common approach in recent years has been to thicken the v-groove area up so that it is substantially larger than the flexing portion of the limb. This serves to reinforce the v-groove, but it reduces the bending area of the limb and creates yet another stress concentration. The result is a lifting of the fibers on the surface of the limb. In all Hoyt’s years of developing and testing limbs, they have only had a couple designs that would survive more than 50 dryfires without cracking in the v-groove. They also perform cycle testing of limbs. This test is performed under the same test condition as the dryfire, except the bow is not released at full draw, rather it is let down softly. In cycle testing of these limbs, they rarely found a limb that would cycle 100,000 times before the glass would begin lifting on the surface. In an effort to eliminate the primary modes of failure in limbs, they developed a design that would utilize two parallel limbs. These original parallel limbs from the same limb composition as the solid limbs improved their dryfire testing from 50 to 1,000. They did, however, find that the lateral and torsional stability of the limb was not as good as the solid limbs. Two years and many, many, designs later, they finally produced a limb that accomplished the original design goals. This limb was a ¾” wide, 5 layer laminated, recurved, split limb with Uniform Stress Distribution called XT2000. These limbs will dryfire over 1,000 times and cycle over 1,000,000 times without any type of failure. This is more than 10 times greater than any other limb they have ever designed or tested. They also found that increasing the overall width of the limb assembly to 2 ¼” wide on the XT2000 limbs proved to be more torsionally and laterally stable than the solid limbs which were only 1 ¾” wide.
Advantages of ¾” Split Limbs: Dramatically increased durability, faster, lighter, quieter, less vibration and more stable.
More Limb Thoughts
Hoyt manufactures all of its own limbs at its facility in Salt Lake City from components purchased from Gordon and other composite manufacturers. They have experimented with many different limb fabrication techniques, materials, and adhesives. The split limb designs have forced them to improve each of these areas to be able to produce four limbs that are identical to each other. I have seen their fabrication techniques and they are impressive. Each limb component is ground on a CNC grinder to a precise dimension. These materials are then laminated together under an incredible amount of pressure. The limb paddles are then cut to width. After the paddles are cut into pieces, deflect each of the limbs individually and match them to three other limbs that all weigh within a tenth of a pound of each other. When I inquired about how that compared to a solid limb, they said that if you take a solid limb and cut it in half, you will find that most limb halves will deflect at least .5 lbs different from one another. They said this results from the natural fiber variance present in the material produced by Gordon and other manufacturers. "
"Thoughts on TEC Risers and Split Limbs
Risers
Material. 6061-T6 is the material of choice for bow risers for several reasons. First, it has very good strength properties, as has been pointed out above. Second, it has an elongation rating which allows it to inhibit stress cracking, and thus keep the riser from snapping. Third, it is commonly available as either a forging or an extrusion that makes it economical.
Advantage: Best blend of strength, weight, and availability
Design. All risers are not created equal. There are fundamental differences in the geometries used to produce risers. A bow riser functions much the same as a bridge over a river does. Its purpose is to hold the limbs in their position and not let them move. Early bridges were made using beams. These beams were often made from 2 X 10 pieces of lumber laid on end and fastened together side by side. These bridges were adequate initially, but as the weight the bridges were required to carry increased, several fundamental design flaws were exposed. First, these bridges would deflect as heavy loads were applied, creating instability at the ends. Second, these bridges had a tendency to “bounce” as they would deflect and recover when the load passed over the surface. Consequently, a new design of bridge was developed. The new bridge designs common today utilize a truss structure, which we commonly refer to as a ”bridge” geometry today. These trusses are built of multiple pieces of material braced together to form the bridge. This design provided a much stiffer member with less overall mass weight of materials. Thus the strength-to-weight ratio of these designs is far superior. As we apply this analogy to bow riser design, we note that most risers on the market are made from a slender piece of aluminum. This design, when coupled with the short, high performance limbs of today, produces a riser that flexes greatly at full draw. Most of you have shot a bow without a bow sling and had it fly out of your hand and bounce painfully on the floor. This phenomenon exists because the riser is deflecting at full draw, where the load on the riser is the greatest, and then recovering when it is shot. Your bow hand can feel the vibration resulting from this deflection and recovery process. Hoyt’s TEC risers have been designed to utilize the principles of a truss. The brace which bridges the top of the riser to the bottom of the riser across the grip area, provides an incredible amount of support to the riser. Consequently, the riser does not flex nearly as far as it would without the support. Additionally, the lack of deflection actually stops vibration at its root—deflection. Hoyt has taken a proactive approach in designing means to prevent vibration, rather than dampen vibration after it occurs. One open handed shot with a TEC bow will illustrate the difference in the amount of riser flex in these bows compared to the rest. Hoyt has done an extensive amount of testing with this design. It is by far the most superior design for risers. It is the reason why Hoyt is the only bow company who can produces cast magnesium risers which do not fail with today’s high performance limbs and cams. All of the Hoyt risers are tested in a dryfire condition which pulls an 80 lb bow to 30” of draw and then lets the string go, at full draw. Every Hoyt TEC riser on the market will survive 1,500 of these dryfires without cracking, bending, or failing in any way. Testing of other brands of product shows there is no other riser design that comes close to these benchmarks.
Advantages of TEC risers: Less shot vibration, lighter mass weight, improved overall bow balance, improved accuracy, stronger riser design, smaller grip, quieter shot, better aiming, and less hand torque.
More Riser Thoughts
Hoyt has designed all of their new TEC risers (2000, 2001, 2002, & 2003) with a Finite Element Analysis software package that allows them to perform simulations of deflection, vibration, stress, strain and other important design factors. They have spent the past three years refining designs that would optimize the factors of weight, deflection, and vibration. The designs they have produced perform very similarly in deflection, and vibration to the risers that in the past have weighed twice as much. The new 2003 bows weigh as little as 3 lb 4 oz, yet shoot like they weigh much more than that. This is due to the optimization of material in the bridge design.
Another fascinating advantage of the TEC riser design is its ability to dampen vibration. There are two sources of vibration. The riser produces vibration that is low frequency and high amplitude. The limbs produce vibration that is high frequency and low amplitude. (I learned this from Steve Sims.) His Enhancer product was developed to take out the low frequency riser vibration. The limb saver and other products were designed to take out the high frequency string and limb vibration. He told me that the Enhancer product does not work particularly well on TEC bows because they have an entirely different vibration profile than any other type of riser. This low frequency vibration does not exist in the TEC bows to the extent that it does in other bows. The high frequency vibration also dampens much quicker in the TEC risers than other risers he has tested. He felt that the TEC risers were designed extremely well from a vibration standpoint. As he worked with the Hoyt engineers to improve their bows, the only significant improvement they could make was to add the limb saver to the limb to reduce the audible noise level of the bow.
Limbs
Material. Bow limbs create many unique problems for designers. They require very stiff materials, however, these materials must be able to flex repeatedly without being damaged. Of all the materials available, none performs as well as glass. There are several different categories of glass ranging from e-glass to s-glass. Each has its own set of performance characteristics. Each is suited to a different application. Carbon is the stiffest material utilized in limb manufacturing today. However, carbon is very brittle and cannot stretch very far without breaking (engineering term is strain). This is the reason why most manufacturers put carbon in the center of their limbs close to the neutral axis, where there is less strain.
Lamination. Laminated limbs are superior to unlaminated limbs in two ways. First, materials can be layered in a manner which suits their material characteristics. Second, the limb can be contoured in a recurve fashion that makes the limb more efficient.
Advantages of laminated limbs: stores more energy, lighter mass weight, increased velocity, increased durability, and increased stability.
Design. Limbs have historically been produced as a single member with a groove cut in one end for the cam, and the other end for the limb bolt. This design produces two stress concentrations at the apex of each of these cutouts. The result is a premature failure of the limb at one of these two areas. Painstaking efforts have been made to strengthen these two weak points. Limbs have been designed with v-groove buttons, overlays, and various other strengthening mechanisms to reinforce these areas. The most common approach in recent years has been to thicken the v-groove area up so that it is substantially larger than the flexing portion of the limb. This serves to reinforce the v-groove, but it reduces the bending area of the limb and creates yet another stress concentration. The result is a lifting of the fibers on the surface of the limb. In all Hoyt’s years of developing and testing limbs, they have only had a couple designs that would survive more than 50 dryfires without cracking in the v-groove. They also perform cycle testing of limbs. This test is performed under the same test condition as the dryfire, except the bow is not released at full draw, rather it is let down softly. In cycle testing of these limbs, they rarely found a limb that would cycle 100,000 times before the glass would begin lifting on the surface. In an effort to eliminate the primary modes of failure in limbs, they developed a design that would utilize two parallel limbs. These original parallel limbs from the same limb composition as the solid limbs improved their dryfire testing from 50 to 1,000. They did, however, find that the lateral and torsional stability of the limb was not as good as the solid limbs. Two years and many, many, designs later, they finally produced a limb that accomplished the original design goals. This limb was a ¾” wide, 5 layer laminated, recurved, split limb with Uniform Stress Distribution called XT2000. These limbs will dryfire over 1,000 times and cycle over 1,000,000 times without any type of failure. This is more than 10 times greater than any other limb they have ever designed or tested. They also found that increasing the overall width of the limb assembly to 2 ¼” wide on the XT2000 limbs proved to be more torsionally and laterally stable than the solid limbs which were only 1 ¾” wide.
Advantages of ¾” Split Limbs: Dramatically increased durability, faster, lighter, quieter, less vibration and more stable.
More Limb Thoughts
Hoyt manufactures all of its own limbs at its facility in Salt Lake City from components purchased from Gordon and other composite manufacturers. They have experimented with many different limb fabrication techniques, materials, and adhesives. The split limb designs have forced them to improve each of these areas to be able to produce four limbs that are identical to each other. I have seen their fabrication techniques and they are impressive. Each limb component is ground on a CNC grinder to a precise dimension. These materials are then laminated together under an incredible amount of pressure. The limb paddles are then cut to width. After the paddles are cut into pieces, deflect each of the limbs individually and match them to three other limbs that all weigh within a tenth of a pound of each other. When I inquired about how that compared to a solid limb, they said that if you take a solid limb and cut it in half, you will find that most limb halves will deflect at least .5 lbs different from one another. They said this results from the natural fiber variance present in the material produced by Gordon and other manufacturers. "
11-08-2002 | 09:25 PM
#2
Typical Buck
Joined: Feb 2003
Posts: 846
Likes: 0
From: In a Tarpon Boat
RE: Good Techie Info...
Frank,
It's a good post and interesting to read about the technical aspects of Hoyt Bows.
But what do you suppose PSE, Martin, Bowtech, Mathews, Merlin etc. would say about their own bows construction if their engineers have their say ?
Not saying that to knock your post or Hoyt but you know how things are.
Everyone thinks they're the king of the hill!
The Mathews and Merlin websites already state why they believe their limbs are the best and superior to split limbs.
To give a couple of examples.
If everything Hoyt says is on the level, then you made the right decision in buying the Razortec.
Actually, most all manufacturers make some pretty nice equipment lately.
That's what competition is all about and we reap the rewards.
Sag.
It's a good post and interesting to read about the technical aspects of Hoyt Bows.
But what do you suppose PSE, Martin, Bowtech, Mathews, Merlin etc. would say about their own bows construction if their engineers have their say ?
Not saying that to knock your post or Hoyt but you know how things are.
Everyone thinks they're the king of the hill!
The Mathews and Merlin websites already state why they believe their limbs are the best and superior to split limbs.
To give a couple of examples.
If everything Hoyt says is on the level, then you made the right decision in buying the Razortec.
Actually, most all manufacturers make some pretty nice equipment lately.
That's what competition is all about and we reap the rewards.
Sag.
11-09-2002 | 12:26 PM
#3
Joined: Feb 2003
Posts: 2,413
Likes: 0
From:
RE: Good Techie Info...
PAB,
Thanks for posting this. There is some stuff in there I hadn't heard before and I wondered about.
I agree with Sag that it is likely that Hoyt engineers are biased. Even so, I've seen a few of the comments from their engineers over the last couple years and never a contrary offering or rebuttal from another manufacturer. Seems to me, Hoyt has a little more confidence in their opinions than the engineers from these other companies.
Thanks for posting this. There is some stuff in there I hadn't heard before and I wondered about.
I agree with Sag that it is likely that Hoyt engineers are biased. Even so, I've seen a few of the comments from their engineers over the last couple years and never a contrary offering or rebuttal from another manufacturer. Seems to me, Hoyt has a little more confidence in their opinions than the engineers from these other companies.
11-10-2002 | 04:55 AM
#4
Thread Starter
Boone & Crockett
Joined: Feb 2003
Posts: 12,157
Likes: 0
From: Lehigh County PA USA
RE: Good Techie Info...
Thank you gentleman for the replies. 
Just for the record, the initial intent of my post on this subject was just to pass info along that I found interesting on a technical subject. The intent was not to say "Hoyt is better...blah, blah, blah...". I know better than to go that route...<img src=icon_smile_big.gif border=0 align=middle>
I just found some of the information interesting.
Thanks again.
Just for the record, the initial intent of my post on this subject was just to pass info along that I found interesting on a technical subject. The intent was not to say "Hoyt is better...blah, blah, blah...". I know better than to go that route...<img src=icon_smile_big.gif border=0 align=middle>
I just found some of the information interesting.
Thanks again.
11-10-2002 | 09:51 PM
#5
Nontypical Buck
Joined: Feb 2003
Posts: 2,299
Likes: 0
From: Central PA
RE: Good Techie Info...
Frank, interesting. I like this in depth stuff. I agree with the other guys, I bet Hoyts engineers are more likely to be biased with their creations. But, I gotta tell ya all, I shoot a Cybertec and Hoyt has their crap together. I shot quite a few, including the Patriot, Legacy, and a few others before settling on the Cyber. It just shot better and felt better to me.
I would however be very interested in hearing from Sims regarding the vibration dampening abilities of their products on the TEC bows. Are they saying that its a different kind of vibration that Sims isn't able to kill, or isn't there enough vibration to really matter?
Just curious
I would however be very interested in hearing from Sims regarding the vibration dampening abilities of their products on the TEC bows. Are they saying that its a different kind of vibration that Sims isn't able to kill, or isn't there enough vibration to really matter?
Just curious
