Question - to any and all Math Majors

[viperryder]

Lifting Idea

There are motors that are called stepper motors. The armature has 360 separate individual steps, so you could move the back a total of any increments of 360 degrees. They can be run off of 12 volts, jus purchase them that way. You could use one or two depending on how you mount them, Good luck.

 

[IdahoMtnSpyder]

The 170 lbs is the total weight of the rear half ( the part we are dealing with ) .... I just weighed the internal metal support Cradle at 28lbs( plus body = 198 lbs total ) ... (this will be bolted to the body, it has the hinges - rod ends ) 90% of the cradle weight is past the Rod ends ...so it actually is a counter weight for lifting measurements ......when all is attached and in place, it only requires 68lbs of force to start the lift towards up-right

That's 68 lbs straight up, right? How far from the hinge is that?

 

[BLUEKNIGHT911]

Lifting my - REAR ...haha

That's 68 lbs straight up, right? How far from the hinge is that?

Yep, of course it's not really straight up ..... it follows an ARC because the hinge is stationary to the car frame ...... the Hinge / Rod ends are 8 inches in from the absolute rear end ..... Mike

 

[Spyder_Cowgirl]

Heading Change

Thanks , I wish I could change the Heading but I can't seem to do it :dontknow::dontknow:..................Mike :thumbup:

Mike …. edit the post and go to "advanced" …. you can change the heading there (at least I have in the past). ….. Ann

 

[IdahoMtnSpyder]

Yep, of course it's not really straight up ..... it follows an ARC because the hinge is stationary to the car frame ...... the Hinge / Rod ends are 8 inches in from the absolute rear end ..... Mike

I should have said at the start of the lift it's straight up. How far from the hinge is that lift point. The distance from the hinge to the lift point times the upward force gives you the torque the spring will have to exert to have zero lift force. If the lift point is at the front end of the half body I think you'll want to size the torque spring so that you have maybe 10 lbs lift required to open the body. That will minimize any bouncing of the body over bumps, etc., which will happen if the spring is strong enough so that zero force is required to start the lift. That is unless, you have a solid snug lock to hold it down.

 

[BLUEKNIGHT911]

Lift force needed

I should have said at the start of the lift it's straight up. How far from the hinge is that lift point. The distance from the hinge to the lift point times the upward force gives you the torque the spring will have to exert to have zero lift force. If the lift point is at the front end of the half body I think you'll want to size the torque spring so that you have maybe 10 lbs lift required to open the body. That will minimize any bouncing of the body over bumps, etc., which will happen if the spring is strong enough so that zero force is required to start the lift. That is unless, you have a solid snug lock to hold it down.

Approx, 64 inches X 68 Lbs. = 4,352 ........... somehow I don't think the Total is correct ...... but the numbers I used to get there are ...... Mike :thumbup:

 

[IdahoMtnSpyder]

Approx, 64 inches X 68 Lbs. = 4,352 ........... somehow I don't think the Total is correct ...... but the numbers I used to get there are ...... Mike :thumbup:

Divide by 12 to convert inches to feet! You end up with 362 lb-ft.

If you reduce the lift to15 lbs., i.e., 53 lbs provided by the spring, that will reduce the the spring torque needed to 64/12 x 53 = 283 lb-ft. That's still quite a bit of torque for your frame to handle so make sure you make it beefy enough! To get a feel for how much that is think about how hard it is to get the Spyder axle nuts tightened to 160 lb-ft!

I think if I were doing it I'd look at a combination of torque spring and gas strut. I haven't paid any real attention to gas struts but there has to be a lessening of the push force the farther the piston extends. Physics dictates that. How much that force reduces depends on the initial gas pressure and the volume change of the gas chamber as the piston extends. I imagine you can find gas struts with ratings all over the map.

 

[BLUEKNIGHT911]

TORQUE ETC.

Divide by 12 to convert inches to feet! You end up with 362 lb-ft.

If you reduce the lift to15 lbs., i.e., 53 lbs provided by the spring, that will reduce the the spring torque needed to 64/12 x 53 = 283 lb-ft. That's still quite a bit of torque for your frame to handle so make sure you make it beefy enough! To get a feel for how much that is think about how hard it is to get the Spyder axle nuts tightened to 160 lb-ft!

I think if I were doing it I'd look at a combination of torque spring and gas strut. I haven't paid any real attention to gas struts but there has to be a lessening of the push force the farther the piston extends. Physics dictates that. How much that force reduces depends on the initial gas pressure and the volume change of the gas chamber as the piston extends. I imagine you can find gas struts with ratings all over the map.

Inches to feet !!!, I had a feeling that was the correct Math ( see I needed Math help :roflblack: ) ....I'm not going to able to reduce the weight by more than 2 lbs ..... I can get very close to 362lb-ft with the Torsion spring sizes available to purchase ....... The rear half - Doesn't have to be Zero lift lb-ft.... I'm still strong enough to get it lifted without ANY help from springs or lift devices :roflblack:.... So 96% assistance is way more than I thought I could get ..... Plus the things ( Elec. screw lifts ) Joel posted about above can be added..... if I only need a little more boost they have a sale on some smaller sizes $ 118.00 per pair:yes:.........Thanks for all your help ....Mike :thumbup:

 

[BoilerAnimal]

Mike, it appears to me that the torsion springs listed on McMaster and Carr's site are in in.lbs., not ft.lbs. The biggest are only ~40 in.lbs., or less than 4 ft.lbs. each. These are relatively small springs, with the largest being .010" bigger than 1/8" .

I know you said you didn't want to use gas struts but check out this video. They show an example that appears to be similar to what I think you are wanting to do, albeit on a piece of furniture. They also give a link to a SGS Engineering's website, where you can play with a design calculator. They are an English company, but the design factors would be the same. You might have to convert your measurements to metric. There are 25.4 mm. in an inch and 2.2 lbs in a kg. Easy peasy!

 

[BLUEKNIGHT911]

INCH - LBS

Mike, it appears to me that the torsion springs listed on McMaster and Carr's site are in in.lbs., not ft.lbs. The biggest are only ~40 in.lbs., or less than 4 ft.lbs. each. These are relatively small springs, with the largest being .010" bigger than 1/8" .

I know you said you didn't want to use gas struts but check out this video. They show an example that appears to be similar to what I think you are wanting to do, albeit on a piece of furniture. They also give a link to a SGS Engineering's website, where you can play with a design calculator. They are an English company, but the design factors would be the same. You might have to convert your measurements to metric. There are 25.4 mm. in an inch and 2.2 lbs in a kg. Easy peasy!

Damn OLD eyes :banghead::banghead::banghead: ...... I didn't see the period , so I thought the measurement was IN - lbs , not inch lbs. ...good catch , I'll call them to confirm ........ I'll check out SGS web site .................Mike :thumbup:

 

[BoilerAnimal]

Sorry, I forgot to put a link up to the video. https://m.youtube.com/watch?v=b8hF87gfPag

 

[BLUEKNIGHT911]

Electric struts

Sorry, I forgot to put a link up to the video. https://m.youtube.com/watch?v=b8hF87gfPag

Thanks ..... I think I've got it figured out ..... I'm going with the Fergelli elec struts .... with shipping they will cost $ 260.00 for a pair .... They are rated @200lbs ea. for a total of 400 lbs. of lift ( this is Dynamic ...Static lift is 800 lbs total :yikes: ) .... None of the numbers I ran come close to this amount , because the strut placement is quite aways from the hinge ( where the lift needed would be a lot higher )....... I started using an EXTENDED length measurement ( which is almost double the re-tracted length ).... The problem with doing it this way, it would be difficult ( at least for me ) to be sure they would fully re-tract :banghead::banghead:.... So I took off one rear tire , which allowed me the see the inside frame completely .... and allowed me to see where my mounting points could be , so there would be clearance and no interference for other parts of the body or frame .... By using the re-tracted length I picked a number of A to B points using different size struts. I opened the body up and then measured to where the ends ( point B ) would be, per strut size ..... I found the length I would need to accomplish a fully opened rear half ...I'm very :yes::yes::yes::yes::yes:............So thanks to all who chimed in ...........Mike :thumbup: