Bumper Build CAD pictures, Dial-up beware!

Hey guys,

Here are some pictures of a project I have been working on to complete my senior mechanical engineering degree. It is your basic spare tire carrier but with the option of two mounting positions for the tire. One will be up high for optimum departure angles off-road and then another position down low to help improve visibility on road. A prototype is in the works but I was wondering what the forum users thoughts are. Part of the project is trying to see what interest their is in the market for a product like this so I figured the best place to get feedback from the off-roading Cherokee market was to go the website that I look at on a daily basis for all my info. Thanks for all your thoughts good or bad.

Side shot of the low position and a view out the back window



Side shot of the high position



Mounting setup with the stock bolt locations being used as well as a strip down the frame rail much like a hitch would bolt on.

A few shots of it opened


View of the rotary latch setup I would like to use

Full view


The gap where you can see the mounting setup from the top will be covered most likely by some thin metal or plastic just so you can't see through. I also plan to mount some D-ring tabs on the bumper in front of where the mounts weld to the main cross-member. Thanks for looking.

This looks like just a basic conceptual drawing. If this is for an engineering project, I would want to see more a lot more details. You may have already done some of this, but here are some things you should consider and questions I would want answered:

- What is it made out of, thickness? How will it be assembled. Internal bracing?
- Bolt holes and hardware? This can bite you in the ass if you leave it until the very end.
- Do those big quarter panel covers just cantilever off of the bumper?
- Hinge design details with loads analysis
- Bracing for receiver and D-rings with loads analysis.
- How is the latch preloaded?
- How did you size the tire carrier tubing and why?

Personally I don't care for the extended quarter panel guards, but it looks nice otherwise. Would you mind sharing the cad file for the body?

footdale said:

This looks like just a basic conceptual drawing. If this is for an engineering project, I would want to see more a lot more details. You may have already done some of this, but here are some things you should consider and questions I would want answered:

- What is it made out of, thickness? How will it be assembled. Internal bracing?
- Bolt holes and hardware? This can bite you in the ass if you leave it until the very end.
- Do those big quarter panel covers just cantilever off of the bumper?
- Hinge design details with loads analysis
- Bracing for receiver and D-rings with loads analysis.
- How is the latch preloaded?
- How did you size the tire carrier tubing and why?

Personally I don't care for the extended quarter panel guards, but it looks nice otherwise. Would you mind sharing the cad file for the body?

Click to expand...

Yeah these are mostly conceptual drawings right now and I am currently in the process of doing some analysis to make sure it is strong enough. The main bar is 1/4 inch thick with 2x4x1/4 pieces that connect it to the mounting points which I'm planing on using the original 4 bolts per side bumper mounts and then an additional 3 or 4 bolts down the frame-rail on each side. All the mounting hardware will range from grade 5 to 8 and will depend on the analysis results. The latch I plan on using is a rotary latch from southco where they are used in car door applications and have to meet pretty high federal regulations. They can handle around 1000 lbs. of force which ensures that car doors don't go flying open when you are in a collision so I'm fairly confident they will work in this application. I got the idea from another guy who used the same type of latch for his tire carrier.

The quarter panel covers do cantilever off the bumper and they are one of the areas I wanted some feedback on because I'm not fully sold on the idea and I think it will look just as nice if I trim them back and they look more like a burly version of the stock bumper caps.

Thanks for the feedback

I would like it if instead of extended 1/4 panel gaurds, they were solid bars to protect the rear 1/4 panels after they have been trimmed. Like this one:

http://www.naxja.org/forum/showthread.php?t=907618

I preffer the low mount tire swing.

Jeepstah,

Looks good! Maybe you could get some extra credit for integrating a high lift mount and gas can mount into the carrier.

This is just a personal preference, but for conceptual drawings I always just use a pencil, a ruler, and grid paper. Some people can create 3d models very quickly; however, I am not one of those people, so I stick to the pencil until I get a concept I like.

Just out of curiosity, what 3d modeling software are you using?

Good luck with your project.

damn, forgot my crayons so i could play along too :banghead:

Personally I'd like to see that rear tire even lower than that. The one showing it in the lowered position didn't restrict approach angles much at all. WIth that being said, Why make it moveable?
Have you measured the departure angle differences? I don't mean to flame, I like the idea of seeing out the rear window and then raise it for off road. But is the extra expense worth the seemingly little gains?

splitz said:

I would like it if instead of extended 1/4 panel gaurds, they were solid bars to protect the rear 1/4 panels after they have been trimmed. Like this one:

http://www.naxja.org/forum/showthread.php?t=907618

I preffer the low mount tire swing.

Click to expand...

I like that idea as well but I was trying to build it as a product that the average consumer could buy and bolt on. Some people get nervous when they start sawzalling thier jeep apart, I know I did. I'm pretty sure I'm going to drastically shorten the 1/4 panel gaurds to look more like the original bumper caps and then people could use just a regular 1/4 panel guard if they really wanted it.

splitz said:

Looks good! Maybe you could get some extra credit for integrating a high lift mount and gas can mount into the carrier.

This is just a personal preference, but for conceptual drawings I always just use a pencil, a ruler, and grid paper. Some people can create 3d models very quickly; however, I am not one of those people, so I stick to the pencil until I get a concept I like.

Just out of curiosity, what 3d modeling software are you using?

Click to expand...

Well its conceptual in the reasoning that I haven't completed the analysis on it yet but I'm in the process of doing that right now. I do have some pretty crappy pencil drawings if you really want to see them haha, but free hand is not my strong suit. We use Pro-Engineer Wildfire at the school here, it is all I have used for 3d modelling even though I have used a little AutoCAD for 2D stuff.

splitz said:

Personally I'd like to see that rear tire even lower than that. The one showing it in the lowered position didn't restrict approach angles much at all. WIth that being said, Why make it moveable?
Have you measured the departure angle differences? I don't mean to flame, I like the idea of seeing out the rear window and then raise it for off road. But is the extra expense worth the seemingly little gains?

Click to expand...

I also would have liked to have gotten it lower but the slider on the inside goes down as far as it can without hitting the main swingout beam as it is right now. I know it isn't a huge difference but I think it is enough that someone might see it as beneficial for the kind of wheeling they do. I'm not sure of the numbers right now but the extra expense isn't much more. I have a business major friend of mine who is going through manufacturing cost predictions that we could use if we were to turn this into a business and I can let you know what we would be able to sell it for and still make a decent living if you are interested. Thanks for the comments from everyone.

Man, I didn't know I said that much

splitz said:

Man, I didn't know I said that much

Click to expand...

Haha, yeah sorry about that. I was trying to answer everyones questions in one reply and forgot to alter the quote code. My bad.

i would say make the low position the high position and the low position lower to be out of the line of sight more and just a thought add a hydraulic
cylinder like the hatch has but bigger because lifting 100 plus pounds of tire sucks just for departure angle the high mount you have now is going to be vey hard on the unibody and mounting hardware up high that 100+ of tire has alot of leverage and bouncing around off road will amplify this but thats my opinion

I've come really close to hitting mine. Dropping of a ledge etc...

Here's mine. (Rigidco)




It doesn't bug me while driving.

edit: I did hit the jack when it was in this position though.