waxhead Posted November 4, 2009 Author Share Posted November 4, 2009 sorry guys i just want to add something ... ive seen the models on the twisting of the bar ..... ive got 260kw atw... it doesnt want to twist it gets pulled down pretty evenly ......the front diff bracket wants to go up thats why its straped down.... ive got wear on the mustache bar from the down right brackets holding the A arms... the diff wants to spin nose over tail if there is same amount of force to each wheel ... so in my oppinion what you guys are doing will work very well but you guys know more about the structure than me clearly Yup thanks for that Its the very thing i was thinking, it wants to lift the front of the diff up. Im going to make a mount for the front of the diff with a rubber block over the top to stop it lifting to far. Your input is appreciated Quote Link to comment Share on other sites More sharing options...
stevo_gj Posted November 4, 2009 Share Posted November 4, 2009 Ahh I see, so the rear of the diff is being pushed downwards like I initially modelled! In that case, now that we have strengthened its resistance to torsion can I suggest you make a couple small changes to the model to increase its strength against transverse loads like the one in the picture I've attached. I would suggest decreasing the size of the cutout near the yellow circles, and removing 'lazy material' where I've put the circle in red. This will allow you to add material to other areas without increasing the weight. I think that since the stress is still concentrated in one location its worth editing the model a little bit more to improve its performance against this downwards loading Quote Link to comment Share on other sites More sharing options...
stevo_gj Posted November 4, 2009 Share Posted November 4, 2009 Ok, in this example each side has two different types of holes. This means that neither side's results are accurate because the stronger side will be displaying higher stresses than it would normally get, and the weaker side will be showing lower stresses than it would normally get. However it IS possible to see the high stress concentrations in the side with many holes. Quote Link to comment Share on other sites More sharing options...
620Z Posted November 4, 2009 Share Posted November 4, 2009 I guess my question would be is why have holes in the bar in the first place. I know visually they look great but I don't see any other purpose. Weight saving in alloy would be minimal. But for every hole you are (per your test model) weakening the overall structure. I am not trying to be negative but get us all thinking. As I would hate to see some produced, sold and break at some point. From a personal point of view my car has 750nm of torque (I know a bit more than most) but you can in fact keep most of that on the ground in 14st gear given the right tyres and road surface. I see on the Arizona Zed model it doesn't have holes all the way through but more indented areas which might be the way to go? Just food for thought. Quote Link to comment Share on other sites More sharing options...
waxhead Posted November 4, 2009 Author Share Posted November 4, 2009 I understand what your thinking But if i want to have it with no holes in it I may as well just have the stock one in there painted alloy colour I was going for the look, the main thrust actually goes to the front mount as this is the point furthest away from the centre of the movement The next thing i am going to do is build a mount that stops the front coming up like the rt ones you can buy Quote Link to comment Share on other sites More sharing options...
stevo_gj Posted November 4, 2009 Share Posted November 4, 2009 Mass of Steel bar: 6.25 kg about 3 times the mass. Quote Link to comment Share on other sites More sharing options...
zedevan Posted November 5, 2009 Share Posted November 5, 2009 I guess my question would be is why have holes in the bar in the first place the holes allow the bar to flex in areas which aren't undergoing the maximum load, and by doing so reduces the force at the maximum points a part we were doing fea on at work was "stronger" when made from 3mm plate than 5mm plate when the designs were identical - but once holes are put in the correct locations in the 5mm plate to allowed it to flex and spread the load, it was ofcourse stronger ...and stevo turn down the deformation scale so it doesn't look so crazy lol Quote Link to comment Share on other sites More sharing options...
stevo_gj Posted November 5, 2009 Share Posted November 5, 2009 It doesn't seem to allow me to do that, do you know where to find that feature in simulxpress? Quote Link to comment Share on other sites More sharing options...
waxhead Posted November 5, 2009 Author Share Posted November 5, 2009 I will play with the drawing more tonight to see if i can get the figures higher Im thinking maybe even cut it out of steel but make the material thiner as well as less metal , ie larger holes with an X in between to give it some strgh Quote Link to comment Share on other sites More sharing options...
stevo_gj Posted November 5, 2009 Share Posted November 5, 2009 Use the FEA above where there are no holes in the design as a guide. The best places to put holes are where the local stresses are low, which are the blue areas. Quote Link to comment Share on other sites More sharing options...
stevo_gj Posted November 5, 2009 Share Posted November 5, 2009 Just been talking to a mate, and he's suggested that steel might be a better material for this particular part since steel has a 'fatigue limit' which means that oscillating low stresses do not fatigue the part over time. Aluminium on the other hand has no 'fatigue limit' and will therefore eventually fail by fatigue no matter how small the oscillating stresses. Since you are kind of fudging the design a bit it might be safer to go with steel. Quote Link to comment Share on other sites More sharing options...
waxhead Posted November 5, 2009 Author Share Posted November 5, 2009 Ok sweet I will work on a new design tonight Steel is cheaper as well Quote Link to comment Share on other sites More sharing options...
stevo_gj Posted November 17, 2009 Share Posted November 17, 2009 This is a thinner steel version of Wax's design. It weighs approximately 4.5 kg. Quote Link to comment Share on other sites More sharing options...
waxhead Posted November 17, 2009 Author Share Posted November 17, 2009 That one looks ok I reckon it would be the go Quote Link to comment Share on other sites More sharing options...
nat0_240_chevZ Posted November 19, 2009 Share Posted November 19, 2009 whats wrong with the std ones? have you had one fail? stock one only weighs approx 4 or so kg's does it no??? remember the stad one is hardened, IE Q & T, so near mech properties of spring steel. you just try & drill it without speciales drilling bits...... R180 & r200 are also different if not already known, holes centres are different. Also mounted the other way, if its had its holes sloted then probly an r180 filed out to suit an r200. just some info for you. nat0 Quote Link to comment Share on other sites More sharing options...
waxhead Posted November 19, 2009 Author Share Posted November 19, 2009 What's wrong with the STD wheels I have never had one break on me ethier Quote Link to comment Share on other sites More sharing options...
nat0_240_chevZ Posted November 20, 2009 Share Posted November 20, 2009 how much more would you spend on machining custom wheels tha off the shelf'os?? no pun intended, im just curious as to why go to such extent when they are available via AZC, yes not cheap but by the time youve destroyed 2 or 3 in product testing, and damage a few other part along the way, namely half shafts or underbody, you probly wasted that cash already. FEA simulation is good, but only as good as the persons/operators understanding of the applied loads and forces, aswell as things like fatigue, eccentric loading and twist of the member once loaded. ie sometimes the fea package doesnot account, either lack of operator inputs or just the transient nature of beam loading, (ie never the same twice...) you may have a bar which is capable of resisting the torque applied, but what if the bar twist slightly, then forces become furthar eccentric to the vertical axis of the bar, the furthar they are the more likely hood of destruction, especially under those 'high load' clutch drops and down changes nearly causing comp lock. just my exp speaking here, if you are to proceed, try making the moustache bar more like a contoured 'I' beam (universal beam), ie have a top and or bottom 'T' flange either billet or stitch welded on, itwill allow far far more bending stress resistance, the wider(higher) the 2 flanges are appart, the greater the bending resistance, try it on the fea package, but as a weldment.... ask me Q's if you are still after ideas. I too have waterjet, plasma & oxy profile cutting and other facilities at my disposal and also have a high demand of torque resistance, hopefully 700-800+Nm however as busy as i am........ cheers nat0 Quote Link to comment Share on other sites More sharing options...
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