My two cents on this one is to use flat parachute chord and backpack type adjustment. Run the chord through appropriated sized and deburred slots instead of bending a chord around a bolt. The point load on the round chord is very high unless you go to a larger bolt cross-section.
regards, Ron On 20.09.2011 04:38, UH-13P wrote:
Have you considered wire rope witha thimble end at the attachment point? It is low cost and easily obtainable at hardware stores. Another option would be hardened steel wire such as clothes line wire or the wire used in vineyards for trellis construction.*From:* Patrick van Gompel <patrick_van_gompel@xxxxxxxxxxx> *To:* python@xxxxxxxxxxxxx *Sent:* Monday, September 19, 2011 2:56 PM *Subject:* [python] Re: Pythonjetrike Thanks guys for the tips and help!Jaculus, can you please clearify so I am sure I understand it correctly. Are you saying that when I put a line around a bolt whitout a knot or anything and I hold both ends, that I can't multiply the line strenght by two? Of course the bolt does give some friction, but aren't the forces on both ends roughly the same? Isn't that how pulleys work? If you pull one end, the other end will move and have the same force to it, or am I completely wrong here?Is a M6 bolt to sharp a bend for a 3 or 7mm thick rope? Please advice.Yes, as you can see in the pictures, the safety line goes through a hole in the tube and is of course sharp. But the primary line goes over a unthreaded bolt part, otherwise I would indeed have much more wear. Wear on the piece of string around the bolts was not the reason for snapping. Of course 150kg is about 1500N. But kg is what they use for kitelines, and probably Newton is for climbing ropes (donno why though). I used kiting knots for attaching both ends, so that the lenght was easy to adjust. Don't know what they are called, but it looks a bit like your example: Clove hitch combined with a figure of eight knot on the lose end. Though, it was the end knot that snapped off. The safety line was of course snapped at the sharp edge of the metal. Now I use a /Square or Reef Knot/ for joining the line ends. Is this a good knot or can I better use your suggested Double fishermans knot? The latter seems more complicated and harder to adjust, but if it gives more strenght...Henry, I checked your dimensions for the swing arm again. Mine are a bit larger, but I have about the same relation: 1:3 for the arms (about 30cm for pivot point to axle and 10cm for pivot point to the link connection point). So 10kg load on the wheel will be 30 kg load on the link going to the rockerarm. Not sure why I have problems with this connection and you don't. My M6 economy rod ends where worn out very quickly (without using the trailer). My double M8 rod ends on the rocker arm have signs of wear too and the 15x15x1mm square tube is deformed by the pulling load. I did buy new M8 PTFE rod ends for the links and M10 for the rocker arm, but I haven't installed them because I was testing the strings. But I am in doubt now whether they are strong enough. This M8 PTFE rod end has a 5.85kN dynamic load rating which is only about double the amount of my worn out M6 rod ends.Thanks for the help, Patrick > Subject: [python] Re: (No From: Jaculus <jaculusbent@xxxxxxxxx> > To: python@xxxxxxxxxxxxx > Date: Mon, 19 Sep 2011 04:32:05 -0400 > From: python-bounce@xxxxxxxxxxxxx >> Being a bit into rope climbing I see some design flaws in your rope set up.> > First of all your rope goes over some pretty sharp metal edges, and a > threaded bolt. Both of these increase wear and tear a lot (especialy > when there is a lot of movement on those spots as I assume there is, > judging from the photo’s). > > Then there is the issue of weakening a rope with knots and alike. As a > rule of thumb you can say the tighter the bend of the rope in a knot > is the more it weakens the rope. This does also apply for places where > the is no knot, but only a bend or an angle, like at the metal edges > in your pictures. > > An other point, two "150 kg lines" (I suppose you mean two 1500 N > lines) do not ad up to a "300 kg connection" it will still be a "150 > kg connection", because the changing loads will be on just 1 of the > two lines in certain moments. > > Then the knot used: please keep it simple, improvising in knots rarely > ever helps. There are plenty of good knots, but to avoiid confusion > stick to simple ones. I would advise you to keep to the following 4 > knots: > - (Double)figure of eight knot. (to thicken rope or make loops at the > end of rope) > - Alpine butterfly. (for loops in the middle of rope) > - Double fishermans knot. (to join two ropes) > - Clove hitch combined with a figure of eight knot on the lose end. > (to attach rope to a piece of wood/metal etc.) > Never have a knot in another knot or in a bend of the rope. And > remember the rule: Keep It Simple Stupid! > > Jaculus > > > 2011/9/19 dirk@xxxxxxxxxx <dirk@xxxxxxxxxx>: > > Hi Patrick, > >> > unfortunately, i don't have a link i can point to, but paragliders have the > > "knot issue" as well. There are certains knots that introduce far less strain > > into the strings than others do. Some can be reopened while others cannot.> > > > Greetings, > > DirkS > > > >> > Patrick van Gompel <patrick_van_gompel@xxxxxxxxxxx> hat am 18. September 2011 um> > 17:44 geschrieben: > > > >> > >> Wow Henry, that looks like a nasty slide... > >>> >> I did cycle quite a bit the last few days and although everything seemed to go > >> fine, I must warn people for the big loads going from swing arm to rocker arm > >> for the jetrike. Today I snapped a double 150kg line! I did have the trailer > >> behind the trike, but it was only loaded for maybe 50kg and not really pushing > >> much on the hook (balanced trailer). I drove into a hole on a dirt road > >> followed by a bump and the primary line and the safety line of the left side > >> snapped. The rear hit the ground and dug into the dirt. The bike is ok and so > >> am I, but I am glad that this didn't happen on the road with traffic behind > >> me. So, a 300kg strong link between rocker arm and swing arm is not enough for > >> my setup. I think I need to go at least twice as high, but preferably up to 1 > >> ton for safety margin. If I were to use quality rod ends, that would mean M12 > >> for size. This size rod ends are quite big and heavy (I use them for the pivot > >> point) and wouldn't like them for the links. I need to find some 500kg > >> strings.... I might try some 5mm hunting rope. Polypropylene is not as good as> >> dyneema, but 5mm is quite a bit thicker than I have now. > >>> >> Anyway, before things broke down, I had a great 75km cycling trip. First, the > >> lines seemed to be damaged a bit by the nut when the rocker arm turned. I > >> fixed this provisionally with a loop under the attached line around the bolt. > >> See: http://cycle.free-creativity.com/images/string_rockerarm.jpg This seemed> >> to work fine. > >> The other end was durable enough and I left it the way it was: > >> http://cycle.free-creativity.com/images/string_swingarm.jpg> >> That setup was nearly wear free for 150km. So I think that pulleys or the like> >> are not really needed. A simple bolt will do.> >> Last Friday I went for a garden job with the trailer (2x20km trip). Including > >> my garden tools the trailer weighs about 50kg and the trike seemed to benefit > >> from the extra load on the hook/rear. Though, the ride felt a bit more bumpy. > >> Handling was excellent, but a bit slower than without trailer. Going to the > >> dump site with garden waste of a total of about 100kg, the trike was still > >> stable and ok to handle, but tight cornering needed more leaning it seemed. > >> Braking with this load with only having a front brake, still felt safe. At> >> least, a test by pulling hard on the brake didn't do weird things to > >> steering/balance or anything. > >> > >>> >> Side note; I just read some stuff about strings/ropes on the internet. > >> Mentioned are safety margins of 5 times the applied load. That means at least > >> 1,5 tons for me! And a knot reduces the strenght to 50%. O dear... I'd better> >> take the 7mm hunting rope. > >> > >> Good hunting, > >> Patrick > >> > >> > >> From: whpthomas@xxxxxxxxx > >> To: python@xxxxxxxxxxxxx > >> Subject: [python] Re: Pythonjetrike > >> Date: Thu, 15 Sep 2011 12:57:01 +1000 > >> > >> Hi Patrick,> >> I concur with your observations. A loss of traction from braking or cornering > >> too hard is a real hazard with tilting delta trikes. Having crashed my Jetrike > >> on one such occasion, once the front wheel went down, I had no time to > >> recover. I took the bike back later and took this photo. You can see the skid. > >> The wider area at the bottom is where my shin hit the ground and the painful> >> gravel rash began :( > >> Best regards to everyone. > >> -h > >> Henry Thomas> >> On 15/09/2011, at 3:46 AM, Patrick van Gompel wrote:I fixed the wheel today> >> and did some more testing.> >> With the fixed rocker arm and strings to the swing arms it works sweet. The > >> simple setup of bolts and nuts as pivot points for the strings is working > >> fine, although I probably need to adjust it a bit for better durability. > >> I did a bunch of heavy brake runs. If the pavement is ok and I brake hard, the > >> bike stays stable, but it is hard to stay in the seat. If you go a bit forward > >> out of the seat the back of the bike will come loose. If I manage to stay put, > >> the front wheel did slip sometimes. But this is at maximum braking and is > >> quite a bit more than I can achieve on my mountainbike. The weak point of a > >> leaning delta trike is when the front wheel is really blocked by the brake and > >> it slips for a longer time. When going straight over a field of grass while > >> slipping, makes the trike rather hard to handle (leaning and steering). When > >> going over dirt/gravel and going into a corner while braking, the front wheel > >> breaks out, which makes the rider fall into the corner. When this happens it > >> seems unlikely to recover from it, although you can put your feet down to > >> prevent falling to the ground. But, compared to a mountainbike when only > >> applying the front brake, the performance is likely the same. So for slippery> >> surfaces I do need rear brakes on my trike.> >> I tested how the trike reacted when leaning to the front. The trike becomes > >> unridable as soon as a shift in leaning to the right or left is needed. This > >> might be because you don't have the grip of the seat anymore to control the> >> leaning, but possibly the changed CoG has the most impact.> >> I changed the steering pivot angle: going up in degrees makes the trike more > >> relaxing to ride and going down makes it more aggressive. I think that the > >> wheelflop had the most impact on this. 65-70 degrees seems like a sweet spot> >> to me.> >> I tested the use of the handlebar for leaning. It is only usefull for stopping > >> and keeping the feet on the pedals. Steering the leaning when cycling didn't> >> feel right and was even dangerous when really trying to. > >>> >> All in all I tested quite a few settings, but it's really hard to get an idea > >> what does what. There are so many variables and while you adjust one, a few > >> others might change too. So if I would make another trike, it would be hard to> >> optimize the design without changing the feel of the ride.> >> For example, I am still puzzled how the steering interacts with the leaning. > >> It is a bit hard to see how the trike leans when riding on it, but with the > >> handle bar for leaning I could feel which way and how much is was going. > >> Steering and leaning seems to go together like a natural thing. Even when I > >> tried to stay in the same position on my seat, the bike still seemed to lean > >> with every corner. I can think about reasons to justify this, but honestly I> >> have no clue. > >>> >> Anyway, I proved it is possible to crash the delta trike, but the feel and > >> stability is really what I wished for when I started to think about a trike.> >> Thanks again to Jürgen and Henry for sharing those great ideas!> >> Now I need some durability tests and get a fully loaded trailer hooked...> >> > >> Happy cycling, > >> Patrick > >> > >> > > > > http://dirk.steuwer.de > > ============================================================ > > > > This is the Python Mailinglist > > > > //www.freelists.org/list/python > > > > Listmaster: Jurgen Mages jmages@xxxxxx > > > > To unsubscribe send an empty mail to > > python-request@xxxxxxxxxxxxx > > with 'unsubscribe' in the subject field. > > > > ============================================================ > > > > > ============================================================ > > This is the Python Mailinglist > > //www.freelists.org/list/python > > Listmaster: Jurgen Mages jmages@xxxxxx > > To unsubscribe send an empty mail to > python-request@xxxxxxxxxxxxx > with 'unsubscribe' in the subject field. > > ============================================================ > ------------------------------------------------------------------------ No virus found in this message. 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