… Roll Over Protection
As one of several mandatory safety devices, the ROP is one of the most important parts, but on the other side it is also a big part of the tractor’s appearance. Thus there needs a lot of thinking to go into the ROP, but it is also a challenge in terms of manufacturing.
The first problem starts when you want to organize the needed material. ETPC rules ask for a seamless steel tube and gives specifications on the dimensions in relation with the material you use. The use of chrome-molybdenum steel (25CrMo4) is recommended, but you can use normal seamless tubes, used by boiler makers, when you go with a thicker wall thickness of the tubes. Knowing that we wouldn’t have a weight issue on the tractor, we could have accepted the 20% extra weight of the ROP and just go with the boiler tubes … well, sometimes you have to set yourself a challenge 😉
How tough can it be? In the literal sense, talking about chrome-molybdenum, we learned our lessons.
Knowing what we want, it was time to call about every steel supplier available in our area. None of them was able (or wanted) to sell us the material we needed. Even a call at a specialized steel supplier in Germany wasn’t successful. With the help of the internet we located a web-shop in the Netherlands, which would even sent the material to us. Apparently, the well known shipping companies are not to excited to ship seven meter long material, so we had it directly cut into the needed pieces, with some spare material … that might be useful, regarding our non-existing knowledge about tube bending.
Tube bending is the next keyword. To bend tube, you need what? Exactly: a tube bender. Not being to confident about buying a tube bender from the PRC, plans were made to build one ourselves. On Youtube and in the deeps of the internet you can find very useful information and creative solutions … or you just know someone in town having and old-school tube bender made in western Europe.
After some measuring and calculations we felt confident and started with the first pieces. Just to have a good feeling, we filled up the pipes with fine grid sand, compressed on both sides of the tube with a wooden plug. The two rear loops with a single 90 degree bend came out perfect, and we were able to take some more measurements to get a good setup for the front loop with it’s multiple bends.
We figured out, that it was all about the perfect alignment of the tube in the machine, doing multiple bends. This said, we marked a 3 meter piece of tube and the disaster started. Here we learned our lessons with chrome-molybdenum … once it’s bend and twisted in the bend, you are f****d. It’s nearly impossible to fix or clamp the tube well enough to correct your bend in any direction.
One piece for the scrap container, of to the next one. We had a steep learning curve and with some corrections the next part came out just perfect.
Time to do all the other little pieces, to finish the complete roll cage. Having all the parts bent, it was time to start assembling. Assembling just works with lots of adjusting, measuring and of course tube notching. Not having a special made tube notcher, we just made a jig for the lathe. This setup is certainly not the safest, but even with doing small steps, you can reach your target.
By the way … even the best hole saw learns it’s lesson the hard way in chrome-molybdenum steel 😉
We were finally able to complete the ROP and we think that it came out pretty well.
Everything is tag-welded in place and will be welded with the rest of the rear axle.