Landracing Forum
Tech Information => Technical Discussion => Topic started by: SteveM on January 06, 2012, 11:22:01 AM
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I'm on the verge of buying a tubing bender for roll cage construction. I have done the search on this forum, and read what I could find. I have read the online reviews, the pro's, the con's, etc. of the various designs.
I am planning to buy a JD Squared Model 3 bender, and 1 die set to get me going. This seems to be a pretty standard bender. I don't want anything "oddball" that I might eventually have problems finding parts for. This is for a basic roll cage construction in my '84 Rampage. Any and all records I have my eye on are all less than 175 mph at present.
The first issue is whether to use 1-5/8 or 1-3/4 tubing. The rulebook states minimum 1-5/8" tubing with nominal 0.120 wall. However, I have also heard (maybe true, maybe not) that inspectors would prefer to see 1-3/4" tubing. Although there is no requirement in the rulebook to use 1-3/4" tubing, what are people's thoughts on this issue?
The second question is which set of bending dies to get. I don't see a need for greater than 90 degree bends, but then again, I'm new at this. The cost of a 180 degree die set isn't too much greater than the cost for a 90 degree set. Is there a reason why either a 90 or 180 degree set would be preferred?
Third - what about the radius of the bends. Are there places in a cage where a 5" radius would be needed, as opposed to a 6" radius? I assume that a 6" radius would generally be stronger in service, and easier to bend without distorting the tube.
Anyway, I'd appreciate input on the tubing diameter, 90 vs 180 degree isssue, and the radius question.
Thanks,
Steve M.
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I don't bend...........but I see a lot of 180s in the cages and roll-bars. It saves on trying to mate two 90s with a weld.
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Steve,
I have the same bender, manual not hydraulic.
It is a tool, in my way of thinking, 180° tooling is a must, if for only that one time you need a 110° bend.
As far as CL radius, I try to design around the larger radius, if for some reason I need the smaller it is 2 days away UPS.
As for tubing size, I think the decision is up to the designer of the cage/car. In real world, the strength (read size) of the tubing is not the real factor, it is the design of the cage. Of course you still have to meet the minimum requirements for the organization you intend to race with and remember, they specify only the minimum size. For myself, the current car is 1 5/8", if I build something else later I may go 1 3/4 or even up to 2".
I will try to find a picture of a collapsed cage, if the tubing size had been larger it would not have made a difference.
John
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These are great benders and I cool group of people running the show there. I live 2 hours from them so I just drove to there shop and picked mine up. I have a 1.75", 1.625", and a 1" and have used them all whether it be for cages, handle bars, furniture, or tools. For the small diameter stuff I would stick to a smaller radius die, no need to have a 10" dia. drive shaft loop. but for the larger diameter tubing I went with a 6" radius die on both if I remember off the top of my head. Go with the 180* dies for sure though. They will allow you much more creativity in your build and you never know when someone will hear that you have a bender and want shock hoops or something bent up, I get calls all the time from the 4x4 guys that populate this area.
Also, be careful about where you mount it and make sure you have the handle (if its a manual bender) around chest hieght. If you mount it too close to anything you end up running out of room while bending things such as a main hoop that normally are over 10' worht of tubing and if it is mounted too high or low you will be sore for days after making a handfull of bends. Also I had some trouble with the chromoly tubing slipping throught the die and ended up buying some shaft collars from McMaster to clamp to the tubing to keep it from pulling backwards through the die. Another trick will be to mark the beginning of your bend with a plumbing style pipe cutter. I just barely put pressure on it and give it one turn around the tubing so that it ever so slightly marks the material. This will keep you from losing the sharpie mark in the shadows or rubbing it off with your hand while putting the material in th bender.
Zach
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I have this bender and have had no problems. I started with the manual but added hydraulic.The reason being the manual model must be anchored to the floor. The hydraulic is self contained. As Zach pointed out location is important. I built a stand on heavy casters which can be stored in a corner and rolled out when needed. I also bought a bend calculator from Mittler Bros. which is a manual and C.D. with a lot of good info. As far as tube size I would always go with more than the minimum required. Safe is better.
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I have a Speedway bender with two shoes & a Harbor freight cheapy pipe bender that I added shims to the pipe shoes to do tubing. The fine china from harbor freight was about $150 & does a good job. I've done five tube chassis with this stuff.
Sid.
http://www.speedwaymotors.com/2nd-Generation-Speedway-Hydraulic-Round-Pipe-Bender,4883.html
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Hmmm, that Speedway bender looks pretty decent, especially if it comes with a good recommendation from an experienced racer. I've been back and forth mentally about which bender to buy. Realistically, this will probably be the only race car chassis I will build for the foreseeable future. If the Speedway bender can get the job done for $300, that would mean more money for my suspension, engine, fire system, wheels/tires, etc.
I'm a bit too leery about the HF stuff.
Steve.
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Steve, you will not be disappointed with the Speedway bender. It's compact, easy to move around & works bitchin right on the floor.
I have a Harbor Freight notcher that will survive three builds & then I toss them. There is a lock pin hole that goes through the middle, I tap it & put a zerk in there & keep it greased. The current one I have, has done a pro-mod chassis & my streamliner chassis & is on loan to a friend right now who's building a tube drag truck. The trick is keep it lubed & run it slooow. I built a frame out of scrap that was lying around & set it up with a slow gear drive hole-hog drill. It's not pretty but works great, kinda like me.
Sid.
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Time for me to jump in and thank you for mentioning Speedway Motors. they're one of the three or four advertisers on the site, paying a bit for the privilege, and I appreciate that you folks out there in Forum-land at least shop at the advertisers. Mentioning them here -- that helps show them that their ad dollars are not being wasted.
So - check out Atomic Speedware and Z Leathers and whichever of the DVD vendors happens to be running. And don't forget Guy Caputo, by the way, and his Tiger Racing products. He was a regular advertiser and has been hit hard by the slowing times - but is working his way back to big time stuff. I see today that he'll be at the Dealer Expo Show in Indy mid-February, and that's good.
Remember - we don't have many ads on here - on purpose. The site loads more quickly this way, and you don't get banner ads flashing and pop-ups popping (or is it pooping) and all of that stuff. Donations are by and large what keep the site running, and I thank you for them. And I thank you for shopping with the advertisers, and I now leave for a little while. Must go ruminate after a fine supper.
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You can learn alot by visiting a chassis shop. There is a very good one in Irwindale, Top Fuel to Jr Dragsters.
He has a JD3 sitting in the center of his floor, enough space around it to manuever long pcs.
Once he works out the details, he has a CNC bender make the production parts.
I used a Speedway/HF floor bender to do rigid conduit for electrical jobs. It is portable, doesn't get in the way, but, I refuse to work on the ground anymore. Its a long reach over the belly.
As I have learned, the bender is only the start. saw(s) notching tools and grinders are also needed.
Buy the best you can afford today, it is a tool that will be around for a long time.
BTW, Speedway has the bender on sale with 5 mandrels for $799 ?? don't quote me, I saw it yesterday.
John
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Is there an Irwindale near Festus MO, or is he going to need to take a drive to CA?
Sid.
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spend the little extra mon-e and get the 32 that will do the 180 deg. I went with 1.75 dies because 1.75 ew is stronger than 1.625 dom and is cheaper to purchase.
UPDATE!!!!! I have tried to find the chart that I based this comment on----and have not been able to find it!!
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Just remember the bender is only as good as the shoes and the followers.
Tom G.
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Have one question about the JD Model 32..Website shows the dies are good for .120 wall tubing, fine if your using .120 DOM but what if I wanted to use .134 EWS for something? Just thinking... :?
Bill
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the 32 can bend 2" .250 that the rockcrawlers use---- and .120 2.5" tubing
I bought the one with the hyd ram and adapted another pump I had. I have 2 inch and 1.75 I have bent a lot of 2" .120 and some .092 .120 and .134 1.75 I have been very pleased---I use "nasty" hi pressure black grease to lube my dies trying to get them to last a long time.
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Bought a used manual Pro Tool with 1" and 1 3/4" dies then ordered the Hydraulic ram and related parts from Pro Tool, good folks to do business with. Ran the ram with the hand pump from my porta power set, slow but got the job done on some cage bends using 1 3/4 DOM mild steel.
Started with using grease then read about using plastic bags so tried that and liked it better, less mess.
Ed
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I have a Hydralic JD Bender w/air over hydralic pump with 1 5/8"-6"radius-180 deg. Die. It makes a perfect bend (no egging). I had one of the guides chip, I called them and they sent me a new one no questions asked.
Richard
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Please consider that when you bend any tube you stretch the outside wall significantly. That means the wall becomes thinner. If you use .120 wall, the wall thickness will be too thin to be legal on the outside of all the bends. So far this condition has been passed by tech. The rule book hasn’t changed on tubing sizes for quite a while but that doesn’t mean the issue hasn’t been discussed frequently. Key inspection people would recommend using .135 wall even though it is not required at this time. As mentioned in another post; the rule book is a minimum.
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spend the little extra mon-e and get the 32 that will do the 180 deg I went with 1.75 dies because 1.75 ew is stronger than 1.625 dom and is cheaper to purchase
Int-e-resting Sparky.......... that is a VERY useful point for new builders.
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Good stuff here.... From a technical standpoint, has it been confirmed that 1-3/4 EW tubing is stronger in practice than 1-5/8" DOM? If so, I would tend to lean towards using the 1-3/4" tubing. I have not yet purchased a bender.
I have also read others talking about the thinning of bends on the outside of tubes, and how they would be under-spec with respect to wall thickness. I have the rulebook in front of me now, and it's certainly not definitive, which is not a surprise. To me, it looks like the rulebook has been written by racers for racers, with a lot of very practical and easy to understand material. A lot of the material in the rulebook can be readily interpreted by someone with some fabrication or racing experience. However, the rulebook lacks the kind of technical detail that you might expect to see in something like a Military or commercial specification for manufacturing or purchasing of specific items.
The wall thickness rule is one of those areas, as is the portion about how to attach the roll cage to the chassis of a unibody vehicle, both of which I will be doing very soon.
The language on tubing is "Minimum requirements for the roll cage structure and the roll cage structure braces are 1-5/8 in. O.D. round steel tubing with a minimum .120 in. nominal wall thickness......" . Certainly, using 1-5/8" x 0.120" walled tubing to make the cage would meet this rule, as the use of the terms "nominal wall thickness" is significantly different than saying something like "tubing must be greater than 0.120" thick at all locations on the roll cage structure". I realize that these differences may seem pedantic to some, but a clear understanding of what is written in the rulebook can be a "make it or break it" difference when it comes to being allowed to race or not. Maybe it's my engineering background, but it would be nice to have a little more detail in some areas of the rulebook.
The other area of immediate interest to me is how to attach the roll cage structure to the unibody vehicle. The rulebook seems to address cages which are bolted in, using a sandwich of 1/4" plates above and below the floor. However, there are no guidelines which specifically deal with welding a cage into the structure of a unibody car. I can find plenty of racers who say they have used 1/8" sheet to reinforce the areas where the roll cage attaches to the unibody, and they have been allowed to race. I'd be interested in hearing from anyone with respect to this item (attaching a roll cage to a unibody vehicle by welding, as opposed to bolting).
Thanks again,
Steve.
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Steve, good point on proving my statment, I have just spent 3 hrs trying to find the chart that I had seen by an online supplier---I can not find it this morning--- so I will just say that I am more comfortable with 1.75 ew than I am with 1.625 dom. I can find 1.75 more easily than I can 1.625.
All so I may add my new lakester has 2' dom in the front hoop that has a 180 with reverse bends set fairly far forward to try to give me more forearm protection.
This is THE MAJOR trade off in lakesters---the ability to get in and out and protect your hands.
Follow up re post:
The way I have done this is to have my cage fairly deep and the front hoop slope back like they wanted which moves the lower attachment point even farther foward, the upper hoop strikes my fore arm about mid way between my elbow and wrist. My upper rail is fairly high because it slopes down toward the nose/frt axle attachment point.
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Steve, good point on proving my statment, I have just spent 3 hrs trying to find the chart that I had seen by an online supplier---I can not find it this morning--- so I will just say that I am more comfortable with 1.75 ew than I am with 1.625 dom. I can find 1.75 more easily than I can 1.625.
All so I may add my new lakester has 2' dom in the front hoop that has a 180 with reverse bends set fairly far forward to try to give me more forearm protection.
This is THE MAJOR trade off in lakesters---the ability to get in and out and protect your hands.
Just spent a few minutes last night talking to Nathan about the same hand protection issue. Glad to see others addressing it.
Steve, locally I can find 1 5/8" .144 wall, plenty of meat left after the bends.
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There are a lot of options available to me for tubing, but I haven't priced them all out.
In ERW, the first items I see are:
1-5/8 x 0.120 - I don't think that's a good choice
1-5/8 x 0.134 - What do people feel about this material?
1-3/4 x 0.120 - Definitely stronger than 1-5/8, but still has the wall thickness issue
1-3/4 x 0.134 - Right now, I'm leaning this direction, but appreciate all feedback
In DOM, the available sizes are:
1-5/8 x 0.120" - wall thickness issue
1-5/8 x 0.134 - seems like a safe choice, but is it better than 1-3/4 x 0.134" ERW, at a considerably higher price?
1-3/4 x 0.125" - is the extra 0.005" of wall section a factor over 0.120" wall material?
1-3/4 x 0.134" - very good material, but almost twice the price of ERW tubing.
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Steve, thanks for starting this thread. That is a good list and I would like to add to your knowledge base to hopefully filter through some of the conventional misinformation. YMMV. First I apologize for not being able to back-up the following with technical references. A recent move has buried all my engineering, design, and technical manuals and I ain’t taking the time now to bring them all together. :wink:
ERW has greater precision and consistent wall thickness than any other type. It is rolled from flat stock and we all know how precise the sheet metal rolling process is. The ERW joint is strong. In the few accidents I have seen at Bonneville I have never seen a failure or splitting of the ERW. (Glenn, if you are reading this I would appreciate your thoughts on this. You have seen it all.) However, due to many variables like poor weld technique, skill, filler rod alloy choice, lack of knowledge, and ego, there have been many weld joint failures that have nothing to do with ERW. The ERW process is a well engineered, controlled, and inspected manufacturing process. I have never seen a failure. There are far more variables in producing a welded joint than the manufacturing of ERW material.
DOM is slightly stronger than ERW in tensile strength due to work-hardening during the mandrel draw. I don’t remember any changes to ductility though. Slight strength increase has rarely been a reason for selecting DOM over ERW due to the increased cost. Contrary to popular belief, wall thickness varies greater than in ERW. Yes that is true. DOM starts out as ERW but during the draw the protruding inside seam is fused into the existing wall. The action of the mandrel, during the drawing, produces inconsistencies in wall thickness greater than ERW. DOM cost is in the region of 2x more than ERW. DOM is usually chosen when a design considers the lack of the inside seam as important enough to justify the increased cost. Telescoping tubing, hydraulic rams, and the like justify the cost of DOM.
I have some rule book concerns as well but due to length I'll do it in another post here.
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I don't think you mentioned the class you are running but you can't believe the amount of cars that add ballast. Typically, less than 1,000 lbs due to the cost of lead :-D but one driver told me they added 3,000lbs to the car! Don't know how true that was . . . you know how racers are :wink:
So if you are going to add ballast anyway, putting weight into your cage can never be bad. Unless it affects the CG location to your determent!
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Edit . . . The rulebook seems to address cages which are bolted in, using a sandwich of 1/4" plates above and below the floor. . . I can find plenty of racers who say they have used 1/8" sheet to reinforce the areas where the roll cage attaches to the unibody, and they have been allowed to race. I'd be interested in hearing from anyone with respect to this item (attaching a roll cage to a unibody vehicle by welding, as opposed to bolting).
No backup plate is needed if base plate is welded.
Steve, this is an old but excellent thread that I think might greatly help in your information gathering. I wouldn’t post to it because some people resent bumping a thread that has died. However, I would like to point out a couple of posts. Look at my picture in post #8 and read Rex’s post #11. The unibody floor in my picture is 0.037” thick because I know that car. My concern is using such a thick plate would impart a shearing action to the substrate. An important aspect of impact attenuation is compressibility or structural yield. That buys you time and allows the G-force to be distributed over more area and more time. I would think, on such a thin floor, you would want the base plate to yield and distort rather than apply a shearing perimeter load on such thin material. However, I don’t have access to FEA so I can’t show a model to SCTA. I have talked to both Lee and Steve about the thickness issue.
http://www.landracing.com/forum/index.php/topic,8446.msg132829.html#msg132829
So as not to be thread jacking, I will start a new thread on my base-plate concern.
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Here's a word from the head handlebar holder of the site and the Forum:
If you want to resurrect an old thread for any half-way decent reason (and the present case seems to qualify) -- you go right ahead and do it, okay? It's fine by me.
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I really appreciate the honest sharing of information on this site. Not that it matters tremendously, but I am a Metallurgical Engineer by profession, and I agree with your assertion about the strength and wall thickness consistency of ERW tubing. The rolling process for flat stock results in VERY consistent thickness of material, which is then rolled and welded into tubes.
From what I have seen specified, the ERW tends to be lower carbon (1008 or 1010), whereas the DOM tubing that I've seen specs for is generally 1018 or 1020 steel. The additional carbon content of the DOM material will account for some of the increased strength (at the cost of slightly decreased ductility).
I did a search on "roll cage" on this site earlier today, and came across that thread you showed about the 1/4" plate welded to the flat piece of thin sheet metal.
Right now, my plan is to weld some 1/8" sheet to the inner rocker panel, which will extend up to the door sill. At the front, nearest to the driver's feet, there will also be the top of a piece of 2-1/2" x 3/16" walled square tubing, which will be the replacement for the stock subframe rail. I want the front roll cage base plate mount to span this gap between the top of the square tube and the inner rocker panel. This piece of plate/sheet will probably be either 1/8" or 3/16" thickness, and will be about 8" x 6" in area. (Does it need to be 1/4" thick, as described in the rulebook for bolt-in applications?)
I'll be interested to read the thread about your base-plate concern.
I intend to run in H/DT for starters, then possibly in G/DT and F/DT.
Steve.
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Yes. The top plate, for either a bolted or welded installation, is identical ¼” thickness. A bolt-in installation requires an additional ¼” thick plate to be bolted underneath. Spanning a gap is unique and may be problematic without FEA or engineering calcs to back-up the design! You should talk to Lee Kennedy and/or Steve Davies for approval before proceeding.
Here is their contact information.
http://www.scta-bni.org/contact.html
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The terms "spanning a gap" is probably misleading and technically incorrect. There will be 1/8" thick sheet already in this position, where the 1/4" sheet will be welded. There won't be an actual gap, (i.e. nothing underneath the 1/4" plate). That description was only intended to indicate that there is about a 6" distance between the subframe rail and the inner rocker location.
The total thickness will be 3/8" at that location, 1/8" of which will be floorboard, and then the 1/4" base plate for the cage. The base plate will be larger than the required 22 inch perimeter size.
Steve.
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This is a dramatic improvement over Ratical! We accomplished this by making the cage area much deeper---it is 18" or nearly 5" over the old car!
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Edit . . . There won't be an actual gap, (i.e. nothing underneath the 1/4" plate). That description was only intended to indicate that there is about a 6" distance between the subframe rail and the inner rocker location.
Understood. What you describe is common. In the second pic an ancillary support for the cage is welded inboard on top of the sub frame protruding into the cockpit. First pic shows another interesting approach. It is the front pax footwell. Note the base plate is welded to the firewall. Another horizontal tube is running backward from there along side the rocker panel. That greatly stregthens the rocker panel and also can be a good attach point for additional cage members.