70 series rear bumper (aftermarket)

[bull]

I have plans in my hot little hand for a custom rear bumper for the BJ70 and selected other models. I'm planning on mass producing some of these and would like some feedback on it.

I was over at Orange Crate's house this weekend and we talked about it at some length.

The main question I have is what do you think about incorporating the passenger side rear ambulance door with the tire carrier.

The idea is to tie it in so that when you open the passenger cargo door that the entire upper piece and tire carrier opens.

There would still be a spindle for support and pivoting. I plan on using the current rear tire holder as the anchor.


My main concern would be that if it is tied together you could back into something hitting the tire, which could possibly cave the door in, unless I come up with something clever.

 

[roscoFJ73]

What side is the passenger side ?
IMO you should have the tyre islolated from the door.
By having the door ,tyre and carrier all connected you will be introducing loads that are competing against each other which will cause friction.
The door which is attached to the body,will want to move different to the tyre carrier which is attached to the frame.
Kaymar and others have been building them for years and thats how they do it

 

[bull]

Yeah I figured that there might be some force issues. I have seen an example that has worked for over 3 years with no ill affects. That is what got me to thinking.. The larger door of the two is the one I'm talking about.

 

[roscoFJ73]

Yeah I figured that there might be some force issues. I have seen an example that has worked for over 3 years with no ill affects. That is what got me to thinking.. The larger door of the two is the one I'm talking about.

Ive never had problems but others consider the big door not strong enough for the tyre for serious offroad use. It tends to wear out the hinges,causing the door to sag a little which in turn wears away the rubber letting in dust and fumes.

The real big problem aftermarket tyre carriers have ,is having a mounting that can swivel and be strong enough.

 

[LDowney]

I like the concept but a have an additional concern. The door hinges do not seem to be up to the task. I would expect that larger than stock tires would get loaded on to such a bumper with integral tire carrier and per your description it would very likely increase the load into the hinges beyond original design. The hinge pins are the same diameter as the pins in the front door hinges of a 40 series truck. The passenger door of a 70 is considerably larger and heavier than a 40 plus the weight of a stock spare tire was added in with the right rear door in a 70. Consequently, it appears that the design margins for these door hinges was used up when the 40 series pin was used in for the right rear 70 door. Consequently, my personal conclusion is it may not be advisable to add more load into the right rear door hinges for the 70.

As a work around, have you given 4-bar linkages any consideration? A 4-bar should allow you to have a tire pivot hinge in the bumper that is not in alignment with the door hinge, but they (door & tire carrier) could move as one. Not having looked at the geometry yet, so this is a guess; my first concept would be to attach the 4-bar to the door via an adapter to the stock tire carrier mounting locations in the door and attached to the tire carrier on the back side of the carrier from the tire. This would slave the tire carrier motion to the rear door, but not transfer the loads into the door hinges. I expect that a latch would still be necessary to lock the carrier to the bumper when going down the road, but once released the tire carrier opening/closing motion would be in unison with the door.

Would it be possible for you to include a drawing or sketch of your concept to help illustrate it?

Thanks

 

[bull]

The load wouldn't be on the door hinges. It would use the hub or spindle as the point of support, yet move as one Ldowney stated. The design I saw is exactly as you described (4-bar). I will scan in some sketches this week. I will also post up a picture of it working on another rig.


I would add an extra latch as a precaution as well. It latches to keep it closed and it will latch to keep it open.

 

[Radd Cruisers]

I did not know that Rosco, got any pics of seven series rear bumper swag.....

What side is the passenger side ?
IMO you should have the tyre islolated from the door.
By having the door ,tyre and carrier all connected you will be introducing loads that are competing against each other which will cause friction.
The door which is attached to the body,will want to move different to the tyre carrier which is attached to the frame.
Kaymar and others have been building them for years and thats how they do it

 

[_Walker_]

My thought is to have something that could survive a good solid hit with minimal to zero damage... maybe extend the bumper back a few extra inches so it protrudes out enough so the bottom of the bumper would be what takes the hit, then there is room to integrate jerry can holders, a winch and an airtank. That being said im not sure how that would effect the approach/departure angles....

 

[roscoFJ73]

I did not know that Rosco, got any pics of seven series rear bumper swag.....

You mean the Kaymar type? They are not very good pics on the 70 list but the 60 series are a little better. A search on google images or aussie forums muight return a better yield.
Kaymar 4WD Accessories

There is also a type used on govt troopies and 105s. It holds 2x16 tyres and split rims ,one in front of the other.
Having a tyre either side of the swinging bar probably helps it by centralising the load.
Im not sure who makes these

 

[seapotato]

yep, I'd also vote for the tire being on a good solid swing out hinge on the bumper, that still allowed the small door to be opened and closed without messing with it.


tire on the door is a bad Idea (imho) as any time some twit in a minivan backs into you in a parking lot and taps that tire that sticks way out, it destroys the back door, and they're kinda expensive, and not all that easy to find in decent shape.

I'll be building a new bumper for my 70 soon, seeing as my cruiser time is now devoted to only one truck....

 

[bull]

update: Orange Crate came over today and we removed my rear bumper and prototyped the rear bumper. I like what we have come up with and it has the ability for a lot of options.

Going to go fish around and see who can cut and bend the pieces I need.

I will post up a pic of the mock up tomorrow.


-bull

 

[bull]

Here is some mock up pics for feedback. I need to take some better ones.

 

[bull]

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[bull]

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[bull]

The reason for the quarter panel step/lip is so that I can put a 1" slider that mimics the lines of the wheel well. It will attach to the sliders. Then I will have one going from the front part of the sliders to the front bumper


The spindle for the tire carrier will sit in front of the passenger side (big door side) blinker. Looking into a low profile spindle so it doesn't take too much real estate.

 

[chukardog]

whats with the gangster lean? Dont you have a 60 bumper to build?. Youre going to mass produce rear bumpers for all 10 of the 70 series cruisers on the road?

That bumper is what im looking for on my 60 Ahem! looks good Rodney. Now get back to work on something pays you money.

 

[bull]

whats with the gangster lean? Dont you have a 60 bumper to build?. Youre going to mass produce rear bumpers for all 10 of the 70 series cruisers on the road?

That bumper is what im looking for on my 60 Ahem! looks good Rodney. Now get back to work on something pays you money.

Ha yeah.. The 60 series is just longer..