foggy3061 Posted May 13, 2015 Share Posted May 13, 2015 Notice where QT reinforce, I guess they have some experience after the failed arms from a few years back... They certainly did have bother! http://forums.lr4x4.com/index.php?showtopic=36190&p=348766 Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 13, 2015 Author Share Posted May 13, 2015 The red arrow is where it's applying gravity, I modelled it the other way up and it automatically applied it and I was too lazy to go switch it back as it's not that important. The Green arrows are rigid fixings, the purple arrows are the applied forces. Let's see what the a fabrication version performs like when I get chance Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 13, 2015 Author Share Posted May 13, 2015 Glad you posted that, the only reason I went for more holes is I thought "if qt get away with it" Are they fabricated or cast? Look fabricated? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 13, 2015 Share Posted May 13, 2015 Yep, fabricated. Never quite fully worked out how they do it, but sometimes has looked like two c-sections welded together back to back. The centre piece certainly appears to be two layers, and the top and bottom have a weld running down the middle. Good pic of the TF arms here, they look much thicker in the middle, but really not sure how they are made!: http://www.landroverworkshopdvd.com/images/landrover_radius_arm.jpg Then, just to throw another option out there, the Adrenalin 4x4 arms are pretty easy to see how they are made: http://adrenalin4x4.co.uk/Castor-Corrected-Radius-Arms-late-Defender-models-1993-2015 Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 14, 2015 Author Share Posted May 14, 2015 I was trying to avoid tube, although it's probably the best shape for the job I would have to buy a full length then fall over the other 4.5m for the rest of time as it gradually gets rustier... unless it was also suitable for a tube front end... Anyway... all done in 5mm weight 6.6kg.4mm weight 5.7kg.I would say the higher stress point under the axle is probably a little artificial as the two bushes are restrained by the axle mount.I think the 5 would be better as it would resist direct impacts on the flange better but I think it might be difficult to form. I have a press though so worst case I should be able to weld a bit squish a bit. I have a friend with qt arms so I'm going to look at those tonight just out of interest. Quote Link to comment Share on other sites More sharing options...
Anderzander Posted May 14, 2015 Share Posted May 14, 2015 Hopefully you won't be pointing out the cracks to him ! Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 14, 2015 Author Share Posted May 14, 2015 No cracks They're interesting, looks like 2 x 5mm pressings welded back to back so 10mm in the middle of the I but only jointed top and bottom by the weld. I forgot to bring my laptop home so I will have to see how they compare size wise tomorrow but I'm pretty committed to the above, I think it should work well. I asked a local machine shop that we push a lot of work through from work to quote for the pins, sometimes if they have a bit of material to get rid of or are a bit slack they'll do you mates rates as a sweetener to make sure the work business keeps coming. £100+vat ea for the pins and £30+ vat ea for the bush bosses. Guess I'll have to buy some material and turn those myself then! Quote Link to comment Share on other sites More sharing options...
Daan Posted May 14, 2015 Share Posted May 14, 2015 I still dont understand how you restraint the chassis end: I see 2 sets of green arrows at the back end, where I would expect one swivel joint. Your stress is completely uniform without hotspots, which in my mind means something is not quite right especially with it being 5 mm thick. Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 15, 2015 Author Share Posted May 15, 2015 The test is intended to represent what the arm will see during axle rotation ie acceleration / braking. It only considers this one action, nothing else. The chassis end is rigidly fixed, the green arrows represent a rigid fixing in all planes. There is an up force applied to one bush and a down force applied to the other. It's not a swivel joint as the force applied to both axle joints are the same however the end one has a greater distance so it would result in continual rotation. All of the forces are applied in the same plane so in the perfect world of a computer it would see no rotation of the arm so a swivel is not required axially. If I wanted the computer to look at true real world all in one go situation I would have to add something to represent the resistance of the bush on the arm, the ground, the spring and the relation the chassis creates between the spring and the bush that holds the arm, the acceleration etc etc. There would be loads of variables leading to uncertainty and the computer would die trying to calculate it. For example it can't do plastic deformation, the calculations just run away exponentially until the computer gives up or crashes. This is a simplification intended to look at one situation and if the same criteria are applied to each design you get a feel for stronger / weaker, add it a bit here, take a bit off there etc. There is a high stress point at the bottom of the arc between the bushes which I don't feel is 100% valid as the two bushes are rigidly fixed together so I would expect some resistance to help counteract this, there is also one underneath which you cant see at the curve where the steering arm goes under which is where it was pointed out by Bowie that QT have reinforced theirs. The problem of high stress points like this is that it stretches the colour scale and smaller changes in stress like along the arm become less noticeable in the colour change. You can put probes at points to try to get readings so I could to that to see how things change along the arm? I was always taught with computer analysis of any sort know the answer first then use the computer to confirm it, I'm not doing that so I can't be 100% certain it's calculating it right, however I have been and measured a QT arm to see how their proven dimensions compare to try give me some confidence. Does that make sense or just twoddle? Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 15, 2015 Author Share Posted May 15, 2015 Well a bit of luck, one of the toolmakers I use at work let me lose on his scrap pile. I have a length of 30mm P20 high tensile tool steel for the pins and a length of 3" Stavax through hardened tool steel for the bosses. I'm just a bit nervous of welding the Stavax as it's stainless, the laser cut bit will be S355 mild steel. I've welded mild to stainless before and had no problems but I'm no welder so it's probably more through luck! Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 17, 2015 Author Share Posted May 17, 2015 I think I know what's going on, just got to wait for it to be announced officially Hmmm... https://youtu.be/3843DQq0GMs Quote Link to comment Share on other sites More sharing options...
Daan Posted May 17, 2015 Share Posted May 17, 2015 The test is intended to represent what the arm will see during axle rotation ie acceleration / braking. It only considers this one action, nothing else. The chassis end is rigidly fixed, the green arrows represent a rigid fixing in all planes. There is an up force applied to one bush and a down force applied to the other. It's not a swivel joint as the force applied to both axle joints are the same however the end one has a greater distance so it would result in continual rotation. All of the forces are applied in the same plane so in the perfect world of a computer it would see no rotation of the arm so a swivel is not required axially. If I wanted the computer to look at true real world all in one go situation I would have to add something to represent the resistance of the bush on the arm, the ground, the spring and the relation the chassis creates between the spring and the bush that holds the arm, the acceleration etc etc. There would be loads of variables leading to uncertainty and the computer would die trying to calculate it. For example it can't do plastic deformation, the calculations just run away exponentially until the computer gives up or crashes. This is a simplification intended to look at one situation and if the same criteria are applied to each design you get a feel for stronger / weaker, add it a bit here, take a bit off there etc. There is a high stress point at the bottom of the arc between the bushes which I don't feel is 100% valid as the two bushes are rigidly fixed together so I would expect some resistance to help counteract this, there is also one underneath which you cant see at the curve where the steering arm goes under which is where it was pointed out by Bowie that QT have reinforced theirs. The problem of high stress points like this is that it stretches the colour scale and smaller changes in stress like along the arm become less noticeable in the colour change. You can put probes at points to try to get readings so I could to that to see how things change along the arm? I was always taught with computer analysis of any sort know the answer first then use the computer to confirm it, I'm not doing that so I can't be 100% certain it's calculating it right, however I have been and measured a QT arm to see how their proven dimensions compare to try give me some confidence. Does that make sense or just twoddle? I personally would put a swivel at the chassis end and restrain the front bolt from going up and down (but not restrain it completely) and put an upward force on the 2nd bolt. This would be pretty representative to what happens. I am not trying to cut holes in your work, hell you're one of the first persons that actually brings FEA to to the table at LR4x4, but if you are going to bring some science into it, then make it representative i'd say. Daan Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 18, 2015 Author Share Posted May 18, 2015 Don't worry about disagreeing, I post on here as I know I will get useful opinions from experienced people By not completely restrain the front bolt do you mean allow it to slide forwards and backwards to allow for 'bend' in the arm? I don't see what a swivel would add at at the chassis end as there won't be any rotation along it's length as everything is applied in a perpendicular plane. You could allow for up/down movement which I guess would be more realistic but you would need to somehow incorporate the resistance of the bush so that it's putting a resistive bend on the arm? I had a stab at seeign what would happen from with a dead stop from 20mph, the forces got pretty scary and it failed. Maybe a dead stop is a bit unrealistic? The tyres probably have 6" of deflection in them and the car would probably jump up or something? Not really sure how to make it a more realistic test? Anyway after looking at the QT stuff which is pretty proven and this design is pretty similar I think I will go for it and see what happens. I patched up the old arms at the weekend and I can't see them lasting long Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 18, 2015 Author Share Posted May 18, 2015 I've ordered the laser cut parts, £30 each. The laser cutters say the grade I've asked for (S355) is only available in 6mm+, the internet says 5mm but I'm happy to go for 6mm so meh! Bending the webs could be fun though... In the end I had the webs laser cut too, my steel supplier didn't have any 40x6 S355 in their UK group so would've had to import it with a delivery time of a couple of weeks. They offered to cut it from plate but they wanted more than the laser cutter. The closest alternative I could've got was EN3B bright which appears to have similar mechanical properties and for the £40 I've paid for the laser cut bits I could've had a full length but I opted for the easy solution of get it from one place and keep it the same. Need to look at making the turned bits now, anyone know the radius arm thread? Best I can measure I think it's M20 x 2.5. I need to buy a die! Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 27, 2015 Author Share Posted May 27, 2015 Well these arrived today, not sure what TA is meant to be for Will be a while before I can get the turning done, shutdown at work = manic maintenance :/ Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 27, 2015 Share Posted May 27, 2015 Ooh, now they look like they may not bend Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 27, 2015 Author Share Posted May 27, 2015 I hope so I'm bored of this job now! Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted June 25, 2015 Author Share Posted June 25, 2015 Finally got the material and made a start on the pins. Ended up with a bit of h13 for the pins which turned lovely, far too good for this job! Ground up an old broken tool to cut the radius at the top of the thread which seemed more interested in getting hot than cutting so maybe a little more practice required there! I've never been very good at parting off so I usually go as far as I dare then cut through with a hacksaw, turn and face off Thread cutting has always been on my list of things to master but decided not to risk it on this job so cut the threads by hand. Either way got there in the end. 2.5 hours for both which is pretty good by my standards Picked this up for the bosses, bit of scrap p20, I'd be proud if that was my turning though if I'm lucky I'll be able to start tomorrow Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted June 25, 2015 Share Posted June 25, 2015 Very nice! Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted July 7, 2015 Author Share Posted July 7, 2015 Got 3 of the bush holders turned so far, there's a lot of material to come out which makes them a bit of a bore! Started to weld one up; Did my best to tack all the rounds bits in square and central then packed the top flange to try get that square too. Then just used the vice to form it around. This is where you find our how square you got everything! For the bottom flange I decided to form the reverse curve first but it was too stiff to do by hand so used an offcut of pipe that I made the front diff guard out of in the press trying my best to keep everything square. Then back to the vice. That's as far as I've got 1 Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted July 7, 2015 Share Posted July 7, 2015 Now that's looking proper, can't see you bending them in a hurry Every time I see a press being used for this sort of thing it reminds me I really should get one! Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted July 7, 2015 Author Share Posted July 7, 2015 It's like anything, getting the press is just the start, getting all the tooling you want can cost a fortune. As you can see my collections is... limited.. lol My hopes are a. They fit and b. They don't bend. Lol Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted July 8, 2015 Author Share Posted July 8, 2015 Tried to do some more but got called out so this is as far as I got. Trying to form the flange that goes under the axle and luckily my now favourite bit of pipe was the right size. Unfortunately I didn't have anything the right size to make an inner former so this 52mm socket had to do as it was the nearest round thing I had to hand. I kept moving the bit of plate around to curve all of it then take the over bend out in the vice. Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted July 9, 2015 Author Share Posted July 9, 2015 Couldn't sleep this morning but didn't want to do grinding so early so decided to take an arm off and see how I was doing. I wanted to lift the back of the diff a little over as the prop was catching the gearbox cross member on droop plus I figured it'd be kinder to the uj. I guess the correct thing to do would've been to modify the gearbox cross member but I figured it wouldn't hurt for what I do. Looking at it now though I think I've over cooked it and gone too high. Opinions? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted July 9, 2015 Share Posted July 9, 2015 Think you wanted clearance to get track rod ends out? Quote Link to comment Share on other sites More sharing options...
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