Lewis Posted February 9, 2007 Author Share Posted February 9, 2007 Due to the nature I would assume 'a' is the direction you're aiming for in which case I would go with the first of your two sketches but would make use of some tubular front shock mounts which would attach to the two upper bars and down to the chassis, with the shock mounts suspended bellow the cross brace between the two top bars. On the 110 the shock towers are 4 inch box welded vertically above the spring cups on the chassis with the shock running inside, these could easily be modified to tie to the wing bars If you wanted to go the whole hog and get a little indepth I could model the options in CATIA and run them through the analysis program to let you know which performs better. Yes please, that would be great if you have the time? I would be very interested in how much deformation the wings and cage would see during a strong frontal impact at 45degrees to cars longitudinal, i.e. hitting a car tree with the corner of the nearside The photos of the tomcat wing would be great if you can get them? Cheers, Lewis Quote Link to comment Share on other sites More sharing options...
will_warne Posted February 9, 2007 Share Posted February 9, 2007 Tomcats are actually very simerlar except they have their wing bars under their skin. Lewis, I think you're design is nearly there. As Bish said, triangles are good. I know some people will suggest having a setup that will deform quite easily I believe that defeats the main reason for going for a tubed front end. However, they do have a valid point that you don't want to have points that will build up massive stresses in a big impact; flailing tubework is not a good idea! The way to get the best of both worlds is to ensure that the loads are spread evenly over as wide an area as possible. Remember now you've got wingbars on top of a cage you've effectivly created a space framed vehicle - the bodywork is only filling in the gaps! Quote Link to comment Share on other sites More sharing options...
markwindsurf Posted February 9, 2007 Share Posted February 9, 2007 Lewis will model up the frames over the weekend if I get a chance, will take rough dimensions off the Tomcat, unless you want me to specifically use your measurements, should be able to give you an idea of how it looks by next week, my email is mark980@btinternet.com if you have anything dimensions wise you particulary wanted to use. The chassis rails will be a little vague as laziness and ease of measuring them will probably prevent me getting them too close, but will treat them as rigid beams which don't bend in the impact probably anyway. Will is dead right on the impact front, all the front end will only be as good as the weld, and would not like to see the welds to the a post breaking loose and coming into the cab... Quote Link to comment Share on other sites More sharing options...
Lewis Posted February 9, 2007 Author Share Posted February 9, 2007 Thanks Mark thats great, I'll go with your dimensions for ease if thats okay? Not being an engineer I wouldnt know which measurement would be applicable Lewis Quote Link to comment Share on other sites More sharing options...
smo Posted February 11, 2007 Share Posted February 11, 2007 Now i'm no expert but surely the brace across the roof on the cage should run the other way above the driver, just like a single diagonalbrace for a hoop always has the top above the driver? Quote Link to comment Share on other sites More sharing options...
Lewis Posted February 12, 2007 Author Share Posted February 12, 2007 Now i'm no expert but surely the brace across the roof on the cage should run the other way above the driver, just like a single diagonalbrace for a hoop always has the top above the driver? Expert? No nor me, but as I'll be sitting on the passenger side then I'll have it this way round Quote Link to comment Share on other sites More sharing options...
markwindsurf Posted February 12, 2007 Share Posted February 12, 2007 Lewis, the model is not quite finished will aim to get it completed today if we are quiet in the office. In the mean time here are some pics of the Tomcat set up, which as I said we use for winch challenge events and gets bounced off trees and rocks fairly regularly. Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted February 12, 2007 Share Posted February 12, 2007 Expert? No nor me, but as I'll be sitting on the passenger side then I'll have it this way round Oddly Nope, Bish is correct MSA Section Q attched showing diag top brace drivers rear to passenger front ! Quote Link to comment Share on other sites More sharing options...
markwindsurf Posted February 12, 2007 Share Posted February 12, 2007 Right here you go front end 3/4 impact direct onto corner of vehicle, impact evenly distributed on the corner. Slightly vague analysis as have just built the cage and assumed rigid fixings to the chassis ( chassis does not move in the impact at all ), vehicle impact is 7 mph with a 2000 Kg car, impact is based on 65000 N against a tree which will only permit a 0.05 M deformation ( hard wood worst case ). However that is all reasonibly immaterial as we are looking at a comparison analysis between the designs. All deformation is subject to a 20 times magnification to make the bend visible, real numbers are shown on the displacement vector graph on the right hand side of the images. Have also included the force diagrams so you can see how the load is distributed through the frame. I have not included a roof cross brace, but would say the brace only functions in support of the system down the length of the tube, if impact is from the other front corner the brace will actually slightly weaken the frame as it will promote locally maximised stresses encouraging the frame to deform, so would put a cross form going front to back diagonally from both front corners. I will post the images up seperately following as otherwise it will be hard to differentiate the different results. Quote Link to comment Share on other sites More sharing options...
markwindsurf Posted February 12, 2007 Share Posted February 12, 2007 Basic original design. First image shows design, 2nd shows forces, 3rd shows deformation Quote Link to comment Share on other sites More sharing options...
markwindsurf Posted February 12, 2007 Share Posted February 12, 2007 Radiator bar cross linking the two sides. this is modeled as welded in which may or may not be possible depending on engine etc. Quote Link to comment Share on other sites More sharing options...
markwindsurf Posted February 12, 2007 Share Posted February 12, 2007 screen bar included. Quote Link to comment Share on other sites More sharing options...
markwindsurf Posted February 12, 2007 Share Posted February 12, 2007 damper mount reinforcement. Quote Link to comment Share on other sites More sharing options...
markwindsurf Posted February 12, 2007 Share Posted February 12, 2007 Then of course there is the analysis utopia, although in reality less than practical, but could be a removable section if the engine was low enough. The deflection drops to a tiny 1mm deflection Quote Link to comment Share on other sites More sharing options...
markwindsurf Posted February 12, 2007 Share Posted February 12, 2007 Then of course there is the analysis utopia, although in reality less than practical, but could be a removable section if the engine was low enough. The deflection drops to a tiny 1mm deflection Quote Link to comment Share on other sites More sharing options...
markwindsurf Posted February 12, 2007 Share Posted February 12, 2007 Then of course there is the analysis utopia, although in reality less than practical, but could be a removable section if the engine was low enough. The deflection drops to a tiny 1mm deflection Quote Link to comment Share on other sites More sharing options...
Peatbog Posted February 12, 2007 Share Posted February 12, 2007 Hi All, Dy'all mind if a newbie chips in? Although i'm a posting newbie on this 'ere forum (one or two of you will know of me from elsewhere) i've been observing for a while and been watching the two wing bar threads with especially keen interest. I thought i'd break my silence to ask the generous Markwindsurf if he would be so kind to repeat his virtual test with an idea of wing bar design i have. If you can let me know if that would be ok Mr...er..Windsurf? thanks Pete. Quote Link to comment Share on other sites More sharing options...
white90 Posted February 12, 2007 Share Posted February 12, 2007 Welcome Pete we were all new once And Mark these posts make this site what it is full of interesting/helpful members. excellent work IMHO Quote Link to comment Share on other sites More sharing options...
markwindsurf Posted February 12, 2007 Share Posted February 12, 2007 Pete, No problem, post up a pic or description of your idea and will have a go at modeling it up and running a comparison against the others. Will try and get into it tomorrow depending on how busy the office is. And white 90 thanks for the feedback. Quote Link to comment Share on other sites More sharing options...
Mark90 Posted February 12, 2007 Share Posted February 12, 2007 It really warms my heart to see people prepared to go that extra mile to help others on company time Seriously, like Tony says it's what makes this place Quote Link to comment Share on other sites More sharing options...
Lewis Posted February 12, 2007 Author Share Posted February 12, 2007 Thankyou Mark for modelling the designs, it really helped me to understand where the deflection occurs with the impact. I hadnt realised that the front hoop is made to take so much force. Looks like I'll be trying to find a way to implement the cross engine brace Thanks again Quote Link to comment Share on other sites More sharing options...
Daan Posted February 12, 2007 Share Posted February 12, 2007 Then of course there is the analysis utopia, although in reality less than practical, but could be a removable section if the engine was low enough. The deflection drops to a tiny 1mm deflection That all looks impressive, but.... Are you guys planning a bankrobbery? Thats just way overkill imho. Daan Quote Link to comment Share on other sites More sharing options...
Lewis Posted February 12, 2007 Author Share Posted February 12, 2007 Are you guys planning a bankrobbery? Thats just way overkill imho. How did you guess Overkill? - no way, just well prepared We need all the strength we can get - You havnt seen my driver drive (neither have I come to think about it) Quote Link to comment Share on other sites More sharing options...
Peatbog Posted February 12, 2007 Share Posted February 12, 2007 Thanks Mark, i'm not so good at trying to describe it, and i dont have a scanner to scan in a drawing. Presumably if you have that kind of programme at work you would have something as simple as Autocad? if so can you ping me your email add. and i'll send you a cad file of it. unless you know of an easier way of course. pete. Quote Link to comment Share on other sites More sharing options...
markwindsurf Posted February 13, 2007 Share Posted February 13, 2007 Lewis, I am actually with Daan in this case, going back to my intial comment if you make the cage too strong it does not do what the cage is designed for which is to reduce the shock passed on to driver and passenger, at 7mph not too much of an issue but at 30 much more of a problem although obviously the frame work deform differently at that speed. Had some time last night so had a little play and will attach it in a moment which might be a more useful / workable solution Note of caution Also in my opinion the hassle value of the cross brace vs benfit would prevent my fitting it, don't forget the brace was modeled as a welded part so some strength would immediately be lost when you bolted it in. The bolt joints would concern me at the bulkhead end, in the case of a hard front impact shearing the bolts and driving the frame through the bulkhead. I would need to be very confident that the impact could be deflected from me and the passenger before even considering it. Also I have just analysed 1 loadcase ( although probably the most likely ) the other impacts I find in competition we sustain is a good knock on the tree bars on the roof and a backing out impact to the rear stays, hence why my roof tree bars now go all the way from the screen to the rear corner, which also means we never get hooked up on trees. Daan, the anlaytical utopia is not always the most practical solution, but it is always interesting to take the development to the extreme just to see what actually happens in the structure, and putting it up may spark a comment from someone suggesting an alternative that I might not have considered. Mark Quote Link to comment Share on other sites More sharing options...
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