ehsnils Posted November 1, 2013 Share Posted November 1, 2013 Any sideways forces (left to right) calculated? I was thinking of the fact that you don't use the rear end mounting points on the vehicle as the OEM hitch do, and as was on this car: http://www.crago.net/subaru/towbar/04.JPG Found an accessory catalog for the '05 with the OEM trailer hitch included: http://www.subaru.se/commonmedia/parts/brochures/legacy/older/Legacy2005EN.pdf Link to comment Share on other sites More sharing options...
frank_ster Posted November 1, 2013 Author Share Posted November 1, 2013 ^ yes good point. so here is in sideways. pull 1000 lb load. the fos is 2.44 so the hitch would yeild at 2400 lbs. this is with the the tow hook attachment bolted. this seems to be the senerio where the tow hook actually helps the strength. with out the tow hook bolted its good for 400 lbs side load to yeild. well that's oem european hitch. the oem usdm hitch is bolted just like this one. and this doesn't require removing the bumper beam and foam energy absorber. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
SBT Posted November 1, 2013 Share Posted November 1, 2013 Interesting. I have the Subaru OEM 1.25" version, and there's no bolt anywhere near the tow-hook. There are some straps that bolt to the frame and to the hitch assembly, but these are on the sides, proximal to the three frame bolts on each side, but there's nothing in the center of the hitch at the tow-hook. - Pro amore Dei et patriam et populum - Link to comment Share on other sites More sharing options...
ehsnils Posted November 1, 2013 Share Posted November 1, 2013 ^ yes good point. so here is in sideways. pull 1000 lb load. the fos is 2.44 so the hitch would yeild at 2400 lbs. this is with the the tow hook attachment bolted. this seems to be the senerio where the tow hook actually helps the strength. with out the tow hook bolted its good for 400 lbs side load to yeild. well that's oem european hitch. the oem usdm hitch is bolted just like this one. and this doesn't require removing the bumper beam and foam energy absorber. I was more worried about possible flex on the two flat sections that anchors to the car and the crossbar and potential metal fatigue on them, but maybe they are thick enough to absorb it. Better to think about it now than when you sit there by the roadside with a metal fatigue issue. Link to comment Share on other sites More sharing options...
frank_ster Posted November 1, 2013 Author Share Posted November 1, 2013 ^ yes totally As long as the loads 1200 lbs tongue and 6400 pull are not exceeded there won't be any fatigue. And 400 lbs tongue weight is a LOT and th car doesn't have enough braking power or acceleration to cause more than 3500 lb in push or pull. The reason for the added safety factor is for bumps in the road. And chugging forward and back that some trailers and loading cause. And this hitch is stronger than any availiable in North America. The European one you mentioned looks good for pulling load but not so much for tongue weight as it wants to twist. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
frank_ster Posted November 2, 2013 Author Share Posted November 2, 2013 more pics from prototype #2 Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
nhltfour Posted November 4, 2013 Share Posted November 4, 2013 how deep is the square receiver tube?! Link to comment Share on other sites More sharing options...
frank_ster Posted November 4, 2013 Author Share Posted November 4, 2013 like 4.75 inches why ? Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
ehsnils Posted November 4, 2013 Share Posted November 4, 2013 ^ yes totally As long as the loads 1200 lbs tongue and 6400 pull are not exceeded there won't be any fatigue. And 400 lbs tongue weight is a LOT and th car doesn't have enough braking power or acceleration to cause more than 3500 lb in push or pull. The reason for the added safety factor is for bumps in the road. And chugging forward and back that some trailers and loading cause. And this hitch is stronger than any availiable in North America. The European one you mentioned looks good for pulling load but not so much for tongue weight as it wants to twist. I was more thinking of the sideways forces as the arrows shows in the picture attached causing stress to the welds and material at the attempted circled points on the picture. Maybe the center mount is sufficient to capture these forces, but I just want to point out potential sensitive points. Link to comment Share on other sites More sharing options...
frank_ster Posted November 4, 2013 Author Share Posted November 4, 2013 ^ yes I totally understand what you saying. But it's equal or better than another North American hitch. And from my understanding cyclic loading will be in the forward reverse and up an down directions. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
Turkeylord Posted November 4, 2013 Share Posted November 4, 2013 ^ Not when I'm running the slalom course with a trailer in tow... Link to comment Share on other sites More sharing options...
frank_ster Posted November 4, 2013 Author Share Posted November 4, 2013 Ill think you will be fine. As I do that on my daily commute to work with all the potholes and broken down civics I need to drive around. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
frank_ster Posted November 4, 2013 Author Share Posted November 4, 2013 do you guys feel it needs to be stronger ? i can add a few gussets perhaps offer a hd model ? but i won't add those gussets on my personal hitches on my two subarus because i don't see the need. the background i have is my brother 83 f250 diesel we made a hitch similar to this out of similar 1/4" material and probably weaker material. i could litterally kick the hitch sideways and it would move a tiny bit. needless to say 10 years of hard labor it never moved, bent or cracked even pulling 2 grain carts of 8 tonnes each. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
Turkeylord Posted November 5, 2013 Share Posted November 5, 2013 Well IMHO, it's plenty strong. Way stronger than any load an LGT should be towing. Link to comment Share on other sites More sharing options...
ehsnils Posted November 5, 2013 Share Posted November 5, 2013 ^ yes I totally understand what you saying. But it's equal or better than another North American hitch. And from my understanding cyclic loading will be in the forward reverse and up an down directions. I just hope that it works out well and no problems are showing up. It's more about "What could possibly go wrong" thinking from my side than actually trying to mess up the design. I think that I have encountered Murphy's law at least one time too many. Link to comment Share on other sites More sharing options...
bettner12 Posted November 5, 2013 Share Posted November 5, 2013 Okay, lets model a emergency braking situation now. Braking 70-0mph 196ft Link to comment Share on other sites More sharing options...
frank_ster Posted November 5, 2013 Author Share Posted November 5, 2013 ^ well stopping power is typically limited to about 1 g. If all the wheels have braking power. So if you add the weight of a 1500 lb trailer your stopping distance is 50% more. And 1g would be down to .75 g And .75 of 1500 lbs would be 1125 lbs of compression your hitch sees. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
frank_ster Posted November 18, 2013 Author Share Posted November 18, 2013 rev c extended the oval for the muffler hangers triangular cutout for less weight and style Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
Turkeylord Posted November 18, 2013 Share Posted November 18, 2013 Looks great! Link to comment Share on other sites More sharing options...
SBT Posted November 18, 2013 Share Posted November 18, 2013 Like the changes. How much does that change affect the structural FEA of linear and nonlinear stress and the fatigue and durability assessment? Does look like there might be a potential for nonlinear stress and fatigue underneath the connection points. - Pro amore Dei et patriam et populum - Link to comment Share on other sites More sharing options...
frank_ster Posted November 18, 2013 Author Share Posted November 18, 2013 Like the changes. How much does that change affect the structural FEA of linear and nonlinear stress and the fatigue and durability assessment? Does look like there might be a potential for nonlinear stress and fatigue underneath the connection points. none , the "hot spots " are around the oval for the muffler hangers and a few others. i extended the radius to maintain the same meat around the oval as before as there was still about an inch of room to the tail pan of the car. hot spots is where it would yeild if the loads i mentioned earlier and the safety factor were exceeded. not the ultimate strength. loading to yeild + a safety factor of at least 1.3 is typical machine safety factors. and this is beyond that. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
frank_ster Posted November 18, 2013 Author Share Posted November 18, 2013 here is the rev c in pull of 10 000 lb .64 fos same as before. if looking at it from a moment perspective the triangular cutouts are further away from the point of rotation. so it has much less impact on its strength. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
frank_ster Posted November 18, 2013 Author Share Posted November 18, 2013 here showing parts below fos of 4 with 10 000 lb load meaning 40 000 lbs is where the area near the triangular cutouts start to turn red. and both of these are without the tow hook part attached. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
nhltfour Posted November 19, 2013 Share Posted November 19, 2013 soooooo.....when can i order?! Link to comment Share on other sites More sharing options...
SBT Posted November 20, 2013 Share Posted November 20, 2013 Any initial estimation on what this will weigh? - Pro amore Dei et patriam et populum - Link to comment Share on other sites More sharing options...
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