Custom box truck ramp design wanted for elise - Page 2 - LotusTalk - The Lotus Cars Community
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post #21 of 30 (permalink) Old 12-28-2017, 04:27 PM Thread Starter
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All this said and done, if I had a lift gate that could lift 3,000 pounds this would be a no brainer. Get some ramp extensions like the one pictured above, and just lift it. That's way cooler than any ramps!
Thanks for that CAD work! I owe you one. My concern with the lift gate was having too large of a moment with the front tires overhanging the end of the lift gate. I think the gate is around 5ft deep and this overhang would be greater than 3000lbs. The truck is getting worked on, and I will post pictures once I get it back.
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post #22 of 30 (permalink) Old 03-14-2018, 10:00 AM Thread Starter
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It's almost spring time! I double checked the box truck height and it is 48" on level ground. A bit lower with ground changes.

I found a set of 5000lb ramps that are 14ft long for a better price without the center posts. Would that be workable or need race ramps?

I owe you one Washburn!
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post #23 of 30 (permalink) Old 03-14-2018, 10:13 AM Thread Starter
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pictures of the truck / lift gate
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post #24 of 30 (permalink) Old 03-14-2018, 03:23 PM Thread Starter
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It looks like a 14ft ramp gives an approach angle of 16.6degrees

Looks like the car has 12.4degrees
Lotus Elise Dimensions, Brochure


I guess I would have to add these in the front...
https://www.andysautosport.com/produ...RR-TR-8XL.html

After seeing the lift gate, do you think bolting some 12ft ramps and using it to lift wold work?
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post #25 of 30 (permalink) Old 03-14-2018, 03:25 PM
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After seeing the lift gate, do you think bolting some 12ft ramps and using it to lift wold work?
Isn't that what I previously suggested?
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post #26 of 30 (permalink) Old 03-14-2018, 03:48 PM Thread Starter
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Yes, I just don't understand how the overhanging load affects the total load on the gate.

Lift gate:
62" deep x 74.5" wide at narrowest point
Car is 2000lbs 38% front 62% rear
Wheelbase 90.6

Rear overhang 27.6 +2" to clear the front lip of the truck floor. Round this up to 30" that means only 32" of surface supporting the car. Most of that will be on the hinged end of the lift gate.

I estimated where the lift gate would end on the car. It's near one of the lift points... The one where the car will "balance"

Thoughts?
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post #27 of 30 (permalink) Old 03-15-2018, 07:48 AM
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So your lift gate is rated for 3,000 lbs and you will be putting 2,000 lbs on it with the weight more or less centered along the back edge of the pad. Do you have specifications from the lift gate manufacturer that lists how it is or could be loaded up to the specified capacity? If not and you are open to experiment, find a vehicle with a 2,000 lbs axle weight (front axle of Accord or Camry?) and place the tires of that axle on the back edge of the lift gate and raise it up a few inches and observe deflection. If it looks solid you should be okay. With the Lotus, the wight will be centered on the back edge of the lift gate but your ramps should cover the full length of the lift gate. The ramps will cantilever the lift gate and help with load distribution. The ramps should be bolted to the front and back of the lift gate.
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post #28 of 30 (permalink) Old 03-15-2018, 04:21 PM Thread Starter
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Correct, I don't have any manufacturer specs about loading. It's designed for pallets I will have to check with them.

The heaviest car I have easy access to is an s2000. Check the pictures, the lift picked it up easily. I didn't want to risk damage of the aluminum gate hinge without asking the manufacturer. In this position there was no deflection at all.

It seems like a statics problem, I'm going to draw this out and calculate the load. Then I will talk to the gate manufacturer about how much the outer hinged portion can take.
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post #29 of 30 (permalink) Old 03-16-2018, 03:19 PM Thread Starter
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Here is an update if this is of value to anyone else.

Alright so let me try to explain this. Im not sure what 3000 lb rating means. Two scenarios are drawn out first in my attachment. If they are trying to make it dummy proof, then in theory you could put 3000 lbs at the farthest point. That means it withstands a max moment of 3000(62) = 186000 lbin.

OR

More conservatively, the gate can withstand a distributed load of 45 lb/in across the whole surface (aka 3000 lb right at the center). The max moment for that scenario is 45*62*62/2 = 86490 lbin.

After checking with the manufacturer the load is distributed evenly.

Regardless, your car would have its rear weight of 1240 at 30 inches and the 760 at 91 (wheelbase) plus 30. The total max moment is the sum of those two. If you do that math, the max moment is about midway between the scenarios above, 129160 lbin.

And finally just for comparison, I back solved based on how your car would be loaded. It would be the equivalent of putting 4200 lbs on your lift gate. Again, NOT safe.

Back to the ramps.... I really wanted this to work.
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post #30 of 30 (permalink) Old 07-02-2018, 11:46 AM
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What if you were to drive your box truck onto ramps then use the 14' ramp scenario? By changing the angle of attack you might be able to use your 14' ramp idea. I back my F250 into a ditch to drive JD lawn tractor right up into the bed when needed.
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