Chaparral2f Posted June 22, 2003 Share Posted June 22, 2003 Does this sound feasable? I have been thinking about building a frame with XKE front suspension for my z-31. The engine is basiclally a detuned sprint car motor (580hp/625 lb tq est.) I need the car to be really stiff. Not being the type that likes lying on my back for months at a time, I want to build a rotiserie, but a 300zx is heavy, and mine has T-tops. I don't want it to fold up if I turn it over. Does anyone know if a t-top body has enough stiffness in the roof to handle being flipped? If I leave the doors on will it give the body any more strength when I turn it over? Thanks Joe Quote Link to comment Share on other sites More sharing options...
280Zen Posted June 22, 2003 Share Posted June 22, 2003 First, I don't know of a rotiserie that would hold a car thats not been stripped down to the frame. Second, I don't think that the car would handle that kind of stress even if you found a rotiserie that would hold a car that hasn't been stripped. Quote Link to comment Share on other sites More sharing options...
David K Posted June 22, 2003 Share Posted June 22, 2003 A stripped z only weighs a few hundred (500-900?) pounds, 280zen. The z31 would more than likely be fine on a rotiserie when stripped completely, just like any other car. Quote Link to comment Share on other sites More sharing options...
280Zen Posted June 22, 2003 Share Posted June 22, 2003 Um Yea thats what I said! This guy asked If I leave the doors on will it give the body any more strength when I turn it over? That tells me its not stripped to the frame! Quote Link to comment Share on other sites More sharing options...
Chaparral2f Posted June 22, 2003 Author Share Posted June 22, 2003 Thanks for all the feedback:) . The car will be stripped to the frame except for the dash. The doors will only be left on if they are needed to add stiffness. I'm not too worried about the rotiserie being strong enough to hold the car(I sppent a couple years working as a welder, and still have a wertification). My main problem is if the top has enough strength. thanks again. Joe Quote Link to comment Share on other sites More sharing options...
280Zen Posted June 23, 2003 Share Posted June 23, 2003 I'd pull the dash off as well, If you can. You wont need the doors on at all, that might cause more problems than anything else, The body is plenty strong enough to be twirled around on a rotiserie Quote Link to comment Share on other sites More sharing options...
Afshin Posted June 23, 2003 Share Posted June 23, 2003 The actual load on the roof does not change when the car is flipped over. When the car is on the ground almost all the load is on the chasis and a small amount is on the roof which remains mostly unchanged when upside down (it can change the direction of load i.e. compress vs extend but not the amount or total force apllied to the roof). Imagine a concrete slab with a tent on top, now flip the concrete slab over, there will still be no load on the tent. For a car think of the chasis as the platform, now even though the roof does take some load unlike the tent example, the amount does not change with flipping of the car. The instance in which the load on the roof would change is when you change the location from which the chasis is being suspended. for example if you put jack stands in between the wheels (eg under the door), you flex the chasis and increase the stretch load on the roof. Conversly if you put jack stands under the bumpers (away from the wheels) you then compress the chasis and increase the compression load on the roof. Since the car can manage all off these scenarios non stripped at over 3000 lbs, you should not have to worry about it on the rotisserie and stripped. Also keeping the doors in will not help since they do not bare any chasis load (only their own weight). Now if I only had the patience to rebuild a car at that level Good luck Quote Link to comment Share on other sites More sharing options...
Drax240z Posted June 23, 2003 Share Posted June 23, 2003 The actual load on the roof does not change when the car is flipped over. Uh, well it does. Maybe the magnitude of force doesn't change, but the roof will be going from compression loading to tension loading. The car may be inverted, but gravity doesn't invert when the car does. Anyway, the car will be less likely to collapse in on itself when upside down than it will rightside up, as something under compression can buckle, but it can't under tension. Imagine a concrete slab with a tent on top, now flip the concrete slab over, there will still be no load on the tent. Your analogy is true, but I think flawed in relation to this question. Imagine a triangulated tressel bridge with a load in the center. Then imagine replacing that tressel with 2 straight beams, without triangulation and apply a load to the center. Bad news. Also keeping the doors in will not help since they do not bare any chasis load (only their own weight). Most modern day cars use their doors for torsional stiffness a great deal. When the door is closed, it completes a box, which is much stiffer than the same box with 2 openings in it. Anyway, back to the first post. With that kind of torque, I would suggest some chassis stiffening is in order. Install a roll cage and you'll have to worry about the t-tops a whole lot less. As far for putting it on a rotisserie, you should be fine if it is stripped. Quote Link to comment Share on other sites More sharing options...
Chaparral2f Posted June 24, 2003 Author Share Posted June 24, 2003 Thanks so much, you guys have taken a load off of my damaged mind. I guess its time to start buying steel. Joe Quote Link to comment Share on other sites More sharing options...
Afshin Posted June 24, 2003 Share Posted June 24, 2003 Uh, well it does. Maybe the magnitude of force doesn't change, but the roof will be going from compression loading to tension loading. Uh, well my post exactly said the same thing "it can change the direction of load i.e. compress vs extend but not the amount or total force apllied to the roof" so I'm perplexed by your response (and I've only had one drink tonight ). Second, when upside down, as you also mentioned the load changes from compresion to tension which can be better handled by the roof. Third the car handles greater compresion and tension loads during driving over dips and bumps, racing and cornering with 2 passengers without the roof ever collapsing or tearing. The jack stand example I gave earlier is another scenario when significant load is exerted on the roof (tension or compression based on location) which again does not damage the vehicle. The whole point being that cars experience significant tension and compresion load on the roof all the time without problem, so having a stripped car on a rotisserie which would cause less load should not be a primary concern. Most modern day cars use their doors for torsional stiffness a great deal. When the door is closed, it completes a box, which is much stiffer than the same box with 2 openings in it True, the doors do add significant torsional stifness. However, a upside down car in not experincing much torsional load. I doubt that the single door latch can have much of a role in preventing the upside down chasis from flexing (that is achieved by the box sections in the chasis and the transmission tunnel wit the roof spreading/balancing the load). Perhaps i should have made it clear that I was reffering to the role of the doors on static load as applicable to this scenario as oppossed to dynamic load or torsional rigidity. I would certainly agree with you if we were talking about driving and cornering, were i would definitely recommend keeping the doors on Quote Link to comment Share on other sites More sharing options...
Drax240z Posted June 24, 2003 Share Posted June 24, 2003 "it can change the direction of load i.e. compress vs extend but not the amount or total force apllied to the roof" I guess I misunderstood how you phrased it the first time. Looks like we were on the same page there. Third the car handles greater compresion and tension loads during driving over dips and bumps, racing and cornering with 2 passengers without the roof ever collapsing or tearing. Sorry if I gave the impression that the roof couldn't handle the loads. I was trying to make the opposite point. As I said, the roof when upsidedown experiences loading in tension, which is LESS likely to buckle than right side up when the roof is in compression. The doors do more than you think. They are made to withstand collisions, and as a result have the loads applied through them from the chassis to mimic how the loads would be distributed if there was no opening in the chassis at all. Also, we need to consider that the car will see more than 2 positions, there are a multitide of crazy angles that might be convenient to work on the chassis. However, I think the weight of the bare chassis really makes it a non-issue on a rotisserie. I also think I was really tired when I read your post because I didn't really get the gist of what you were saying. Quote Link to comment Share on other sites More sharing options...
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