CBHVerticalTubing Bender - (CBHVTB)
As many readers know I'vebeen using and building tubing benders for about 40 years now and I have someopinions about what makes or breaks a bender for doing production bending workand I've always preferred to use a 'horizontal' style manual bender.
However when I moved intothe new Texas shop I realized right away that there was no way that I'd haveroom for a conventional horizontal bender like the JD2 model 3 or the Pro-Toolsmodel 105 which are two of my favorites.
As a result of thissituation I started to take a serious look at buying or building a smallvertical type of bender that I could tuck away in a corner of the small shopwhen it wasn't being used.
I bought a couple of plansand downloaded free plans from the net for several different vertical bendersand then I went around to shops and dealerships to see some of these machines inaction and to be honest I wasn't to impressed with what I saw. The best ofwhat I did see were home made models but even some of these had limitations.
A lot of the verticalbenders are marketed using what I'd call 'fantasy-wear' where themanufacturer makes some wild-assed claims that simply can't be substantiatedin reality. At one sales demonstration I actually saw a bender frame buckle oversideways just trying to bend some 1.5 x .25 wall DOM tubing and the model theywere demonstrating was their supposedly 'heavy-duty' model. They blamed thefailure on the Pro-Tools die which they said had a poorly cast pivot pin holewhich even an idiot could tell wasn't the case. Most of us at that democlearly saw that the unrestrained ram shaft was moving towards one side of thedrive links causing a twisting and binding situation that the operator shouldhave taken care of. That experience immediately soured me on looking muchfurther at mass-produced vertical benders since the unit I was looking at was supposed tobe the 'ultimate' bender. Ironically the maker came out with an'improved' model a few weeks later that had much thicker arms.
I was also extremely disappointed to find out that almost all vertical benders that I saw demonstrated needed to have the drive links reset just to do a simple 100-degree bend which is about what you need to do in order to get a good '90' after'spring-back' is taken into consideration. I could not believe that thesevarious bender manufacturers and designers didn't have a clue about the mostbasic fundamentals of making good tube bends.It was pretty obvious that selling a 'canned' product was far moreimportant that selling something that was useful and actually worked in theenvironments of a small fabrication shop.
To me having a bender thatneeds the drive links reset after turning a 60 to 70-degree bend was just anon-starter with respect to serious fabrication work. Even guys just startingout with a bender realize that the biggest reason for 'kinking',wrinkling' and 'distortion' is due to spring-back and every time you haveto reset the drive links you are letting the tubing 'relax' or'spring-back' and when the drive links are re-engaged there will be a slightindentation in the tubing once pressure is reapplied.
None of the verticalbenders I looked had any provision for adding one of the various anti-springback devices like we typically use on horizontal benders.
This simple design flawwith vertical type benders is one reason that they have not taken a market shareover the old traditional horizontal benders in the commercial fabricationindustry.
As I mentioned earlier someof the best vertical benders I saw were custom made in small shops and most ofthese had incorporated workarounds about the bending angle problem.
It was pretty obvious to methat some bender manufacturers where pretty good at having parts water-jettedbut not so good at actually bending tubing so I went back to the plans thatI'd originally downloaded since most of them were drawn by guys who actuallyhad to bend some tubes in a real-world environment.
Myfirst choice of the home-brewed benders based upon recommendations by dozens offabricators was the little Pro-Tools model HMP-200 but after I reviewed theplans in detail and built a mock-up it was immediately apparent that this benderhad some rather significant limitations so I put that one away on the shelf.
This is a good low-cost bender but Idon't think that it works very well in a production fabrication environmentand it's relatively expensive to build.
Thenext bender I took a look at was another one recommended by a lot of people andthat was the AH-Bender designed by Frank Takacs known to most of us as'EuroFrank' at the boards. The plans for this bender have been around a longtime and have gone through several stages of refinement and improvement.
Ihave yet to talk with anybody who uses one that doesn't have anything but goodstuff to say about them.
Sincethis bender had such a good reputation I didn't even bother looking at theplans in detail with respect to operational issues and went ahead and built one.This is an excellent bender but it didn't end up meeting one of my primaryrequirements and that was making a 110-degree bend in one clean sweep withouthaving to reposition the drive-links. My other issue was that the unit wassimply to low to the ground so that I always had to stoop over to load tubes,set the die and follower and position the digital protractor. I ended up usingthe bender while it was sitting on top of two plastic milk-crates and then it'felt' great.
Theother drawback was that this bender is designed to use the Pro-Tools Model 105die sets and I much prefer the JD2 dies especially for bending thin-walledmaterials and stiff material like chromoly.
Whileresearching vertical benders I had a chance to use a machine based upon one ofFranks very early models (the HD-Bender) and to be honest I much preferred it tohis latest version. I think that the plans for his original benders are stillavailable and if you're serious about building a bender I'd suggest that youbuy both sets of plans if at all possible. Franks site is: http://www.gottrikes.com
Vertical Bender Geometry
Buildinga vertical bender that uses a hydraulic ram is a whole lot different thanbuilding some of the other benders that we've posted fabrication plans for.The biggest issue and a significant restraint is the hydraulic ram itself.
Almostall vertical benders including some of those high-end models you see advertisedon the Net use cheap imported 'air over hydraulic' long throw 8-ton rams.The physical dimensions and characteristics of these hydraulic rams actually setmost of the design parameters a person can come up with when trying to build abender.
Anotherproblem with 'cheap' hydraulic and air over hydraulic rams is that most of themdo not function unless they are mounted in such a manner as to have upward slopeto the cylinder.
'Alltrade'in Southern California distributes the ram I used for my particular projectunder the brand name of 'Powerbuilt'. This ram is sold by dozens of retailoutlets under some other trade-names but in almost all instances it is just oneof a dozen Chinese clones that make their way to America. Some of these brandedclones are verging on being pure junk and others are actually quite well made.It pays to shop around and buy your parts 'in person' so you can actually'see' what you're getting.
Ingeneral almost all of these cheap rams have a capacity of 8-tons with an airsupply of 110-120 psi. The minimum saddle height is 24.5-inches and the maximumsaddle height is around 43.5-inches which equates to a stroke length of19-inches. There is nothing wrong with the capacity of these rams with respectto the force applied to the drive links. In reality an 8-ton (16,000psi) ram ismassive overkill since it only takes about 5000psi to bend 2-inch diameterheavy-walled tubing in a typical bender.
Bewarethat the stroke length is usually less than what is published. My particular ramhad a useable stroke length of only 18-inches and I think this is fairly typicalfor the lot. Most of these rams have what I call a 'deadzone' at thebeginning of the stroke, which shortens the effective stroke length by as muchas an inch. There is a corresponding 'deadzone' towards the extremity of thestroke at full extension.
I'vealso the seen the minimum saddle height for these rams range from 23.5 to25.5-inches depending upon a particular brand. For this reason I stronglysuggest that you buy and measure a ram before doing anything else if you'replanning on building one of these benders.
Figure 1
Figure1 illustrates the primary dimensions used to describe the characteristics of atypical long-stroke air/hydraulic ram. As you can see the 'minimum saddleheight' is the distance between the centerline of the base mounting boltholeand the center of the pivot pinhole in the ram shaft. When the ram is fullycompressed. The 'maximum saddle height' is the distance between the mountingbolt center and the pivot pin in the shaft when it is fully extended. The'stroke length' is determined by subtracting one number from the other.
Whenyou set up the control points for a vertical bender you're basicallyinterested in working with three dimensions that define points on the radius ofthe moving parts of the assembly.
Thefirst control radius is that established by the minimum saddle height of the ramthat you're using as seen on the left in Figure 2. In this case we're sayingthat it is 25-inches.
Figure 2
The next control point is the one thatlays on the radius of the fully extended ram shaft as seen on the right inFigure 2. In this case we're saying that it is 42-inches from the center ofthe ram base mounting bolt. Keep in mind that the ram pivots as it moves throughits range of extension. A lot of first-timers forget to take this into account.
In this particular exampleour stroke length is 17-inches.
The two fundamental radiiwill never change no matter what you do to the ram that you buy. You can movethe mounting point of the ram up or down or left to right but the radius pointswill always remain constant relative to the base of the ram unless you change toa ram having different stroke characteristics.
The next radius point wehave to consider is that defined by the length of the drive links. This ispretty simple to calculate since we know that the drive link pivot pin or pinshave to be coincidental with the arcs formed by the movement of the ram shaft.
You don't need long drivelinks in order to create bending torque with a hydraulic unit like you do whenbuilding a manually operated bender. The drive links on my little prototype areonly 10-inches long and I bend 2" by .188 wall tubing all day long with thisconfiguration.
Figure 3 illustrates therelationship of the drive link radii with the ram shaft radii for two differentconfigurations. The design on the left in the illustration has drive links thatare 10-inches long and the design on the right has a set of drive links that are16-inches long.
Figure 3
Note that the radius of the ram shaftpivot point in the fully compressed mode coincides with the pivot point of thedrive link pivot pin when the bender is at the 'start of bend' position.This is pretty elementary stuff but I don't think anybody has ever coveredthese basics before so I just want to make sure everybody is fully aware of thefundamental operational characteristics of a typical vertical bender beforegoing any further.
Now the fun begins because we have tocome up with a bender design that can bend a specific tubing size to a specificangle at a specific centerline radius with the least amount of hassle possibleand this involves some compromises.
A lot of folks go out and build theirbenders based upon a false assumption that once they have the ram and drive linkarm pivot points coinciding then everything else is good to go but that'ssimply not the case.
The ram shaft is a physical object andyou have to take the location of this shaft into account as the ram movesthrough the full range of motion. The design length of the drive links and thepivot hole location for the ram shaft in the drive links are determined to ahuge extent by the size of materials that you plan on bending.
Figure 4 illustrates a typicalvertical bender shown with the drive links rotated a full 110-degrees. In thisparticular illustration the bender is set up to bend 1-inch diameter tubingalong a 3.5-inch radius. The length of the drive-link is 10-inches in thisparticular example.
Figure 4
This configuration of 10-inch linksusing a typical ram will work just fine on tubing up to 1.25-inches in diameterbent on a 4.5-inch centerline radius. You can make a nice 110-degree bend in oneclean sweep without having to reset the drive links.
So you don't have to start fromscratch I can tell you that based upon actual field experience and mathematicalcalculations a hydraulic bender using an 8-ton ram with a set of 10-inch drivelinks can easily bend 2-inch diameter thick wall tubing. So a longer set ofdrive links are not needed to create additional bending torque.
However longer links are indeed neededto make room for the ram shaft to 'clear' the tubing in the die as the bendsare being made in larger tubing or tubing bent on a larger radius. The ram shaftwill actually bump into the tubing at some point during the die rotation, whichwill jam up the whole machine. This is the single biggest issue facing thedesigners of vertical benders. We can blame it all on the relatively short18-inch stroke of most cheap long-throw hydraulic rams. If we could get a fewmore inches of stroke length then bender design would be a whole lot easier.Unfortunately going up in cylinder size to get that longer stroke length costsbig bucks and for most small fab shops this is the deal-breaker.
Figure 5 shows a typical bender set upwith a die set for 2-inch tubing bent along a 6-inch radius but still using theshort 10-inch drive links.
Figure 5
As you cansee the shaft of the ram will actually bump into the tubing if you try to make acomplete bend in one sweep. To use the short links with larger diameter dies itbecomes necessary to reset the drive links so you end up making a series ofshort bends to make a final longer bend. This will work but it's reallyinconvenient. Unfortunately this situation is exactly what you end up with whenbuying some of the mass-produced vertical benders on the market today.
A better wayto handle this situation is to just use longer drive links to begin with butthen another problem comes up.
As the drivelinks become longer the effect is to reduce the amount of rotation possiblebefore the ram reaches its maximum extension point.
Figure 6illustrates this situation using a bender set up with a set of 18-inch links,which are fairly typical on a lot of vertical benders. Using this type ofarrangement you can bend up to 3-inch diameter tubing on an 8-inch radius diewithout much problem.
Note howeverthat you can only make somewhere between a 70 and 80-degree bend with these longlinks before you need to reset the links on the die.
In effectthe ram simply can't extend far enough to continue making the bend much pastthe 80-degree point on most benders. In fact many of both the commercial modelsand the home-built models can't make a bend beyond the 70-degree point withoutrepositioning the links on the die.
Figure 6
As Imentioned earlier, from my standpoint the single most important bender designelement was the ability to make at least a 105-degree bend in tubing withouthaving to reset the drive links. Ifyou do any handlebar or exhaust header work the reason for this should be wellunderstood.
To meet thisrequirement it will become necessary to use links that are somewhere between 10and16-inches long and it will also become necessary to 'offset' the ramshaft bolt location relative to the centerline of the links themselves. If yousearch the net you'll see that this what almost all manufacturers do to createa bender that works over a broad range of tubing sizes and die diameters.
The reasonfor this long discussion on basic geometry is because I know that almosteverybody who builds a bender based upon our plans will most probably modify itas much as possible to suit their specific requirements. Armed with thisinformation they can make better design decisions without having to resort to alot of trial and error experimentation.
The hydraulic ram I usedfor this project had a 5/8" diameter bolt hole bored into a 1.5" shaft. Thisis a fairly typical arrangement but I have seen similar rams using a 1.25"diameter shaft bored for a 3/4" pin as well as cheap rams using a 1" shaftbored for a 1/2" pin. Before you drill anything, double check the actualdimensions of the particular ram you end up using.
It is actually a good thing to borethe drive link hole for the ram pin slightly oversized, as this will allow youto seat the die follower by hand without having to actuate the ram unit. Forinstance if you have a ram using a 5/8" pin then drill the drive link rampivot hole to 3/4". This tip is not shown on the plans.
It is critical that you attach the ramshaft to the drive links so that the shaft is always perfectly centered betweenthe plates of the drive links. Thebest and maybe the easiest way to do this is cut and cope some tubing spacers tofit inside the drive links instead of using washers or free-floating spacers.I'm still using washers as shims on my bender and it works but it's a reallypoor way of doing things.
Summation
I haven't had time to finish theactual building steps for this new bender but I've had so many inquiries aboutmounting the old model vertically that I thought I'd post this now and finish*t later.
I built the original prototype forthis bender from scrap materials and it worked so well that I haven't botheredto build or photo-document a final version yet but here's a photo of the workingmockup.
You can see here that the bender caneasily extend to do a full 110-degree bend in a single stroke without having toreset the drive links and even though the die is not installed in this picturethere is plenty of clearance for a 2" die having a 6-inch centerlineradius. I'm pretty sure this version of the CBH vertical bender is the onlyvertical on the market with this capability.
In this photo you can geta better idea of the overall size of the unit. I didn't bother to put casters onthe prototype but it's still easy to drag around the shop. About the only changeI want to make on the final version is to add a remote pressure release valveand a 'return' spring for the drive links.
I've been making a lot of handlebars lately and I've found that I can install 2 one-inch dies side by side and get identical bends in two different bars at the just one pass which is kind of handy.
I'm thinking about makingthe links and frame for this bender from 5/8" plate so it can be mountedvertically or horizontally and operated manually or with air/hydraulic assist.
The plans are, like mostof our stuff large format prints so you'll need to take them down to Kinko's toget them plotted. Even though the plans were drawn primarily for my own use inbuilding the prototype I think that most people will be able to figure outthings I might have left off the drawings.
I'll keep updating thismaterial and revise the plans as we start to build some final units for somelocal shops.
The download links for the plans are:
https://chopperbuildershandbook.com/VTB1-1.pdf
https://chopperbuildershandbook.com/VTB1-2.pdf
https://chopperbuildershandbook.com/VTB1-3.pdf
https://chopperbuildershandbook.com/VTB1-4.pdf
https://chopperbuildershandbook.com/VTB1-5.pdf
https://chopperbuildershandbook.com/VTB1-6.pdf
The following links may beof interest to folks building a new bender.
http://www.blindchickenracing.com/tools/tube%20bender/tubingbender.htm
http://www.mechwerks.com/Mechwerks_plans_drawings.htm
http://www.gottrikes.com/Tube_Bender.htm
http://www.jd2.com/c-12-benders.aspx
http://www.pro-tools.com/tube-and-pipe-benders.aspx
http://www.jmrmfg.com/tag/tube-bender/
After you download the plans a donation is appreciated, no matter how small, to help keep the site alive and the plans freely available.
