Process Improvement – Page 11

January 10, 2012January 17, 2012

Second Prototype Gas Tank Skid Plate

I liked the skid plate I fabricated for Jennifer’s XJ so well that I decided to make one for my Jeep. I did however make a few changes in the design. I did not like the way I bolted hers in place by tapping into the thin metal frame rails. One of the bolts stripped out and had to be replaced with another one near by. I have bought rivet nuts to strengthen it next time it is taken off her Jeep.

For mine, I decided to fabricate a bolt strip to insert inside the frame rail. To make the strip, I first had to remove the rear bumper. This is easy on my off road Jeep due to the way the custom pipe bumper is made. I also took this opportunity to remove two broken off bolts in the bumper mounting surface.

The first one was accessible from behind the bolt hole so I simply clamped vise grips onto the end of the bolt and turned it out the back. I did have to use some heat and penetrating oil to get it to turn but one it did, it came right out the back.

The second bolt was at the top and I could not access it with vise grips. I could however spray penetrating oil on the exposed part. I first tried cutting a slot in the bolt and turning it with a screw driver. That did not work at all. Next I made a deeper slot and tried my impact driver. I was able to turn the bolt about half a turn before it stopped again. Even heating it cherry red did not help.

Next I took a nut and welded it to the broken off bolt. I used my flux core wire welder to make the weld. The bolt came out relatively easily with the nut welded to the top.

I measured for the two holes that were already in the frame rails. I then marked an approximate location for the third bolt. I drilled the holes in the angle used for the mounting bracket. I then made a strip of flat bar with the same hole spacing using angle as a jig. I then welded in two bolts into the holes that lined up with the two in the frame rail. I used a magnet to slide the strip into place and temporarily bolted the angle in place. I then drilled through the hole in the bracket into the frame rail. I then removed both parts and welded in the third bolt.

I repeated the procedure for the other side. I had to open the hole at the rear of the Jeep slightly to get the strip inside. I used a cut off wheel to make two vertical slits and then bent the metal out to open the hole enough to get the bolt strip in. Fishing it under the gas filler section was challenging but it worked.

With the mounting points fabricated, I used the template from the first skid plate to lay out the side pates. I extended them about a quarter of an inch to give a little extra clearance when installing the plate. The bottom plate ended up about a half inch wider. I am not sure how that happened. However, I like the extra clearance on the side of the tank.

Another change I decided to make was the exhaust hanger. Jennifer’s uses the exhaust hanger bolts as mounting bolts. However, these proved extremely difficult to install when mounting the skid plate. For mine I fabricated studs and welded them to the mounting angle. Now I can simply slip the hanger over the studs and install two nuts. I expect this to be much easier.

I currently have the sides and the bottom tack welded together. My next step is to remove the assembly from the Jeep and complete the welds. I picked up a new roll of wire for the welder today.

UPDATE: Last night I took it down and did the final welding. I finished off the spool of wire that came on my MIG so I had to learn how to change wire in the middle of the welding process. I ground down the edge and now it is ready to be sanded for paint.

UPDATE 2: I added a small lip at the front edge that adds a lot of strength to the plate. I also sanded it down and painted it black.

January 5, 2012January 5, 2012

Jeep Cherokee Thermostat Replacement

On the last few cold mornings, I noticed the heater in my Jeep Cherokee was not putting out heat like I wanted. I also noted that the temperature gauge was not reading as high as normal.

I knew that the thermostat must be opening too soon. The only cure is to swap it out.

I picked up a Stant Supersat at Advance Auto. I used the order online – pick up at the store option to save a couple of bucks.

My Jeep is equipped with a K&N air filter and intake tube so I don’t have an air box in the way any more. I loosened the power steering pump and moved the drive belt out of the way of the thermostat housing. I have done it without loosening the belt but it is much easier with out the belt in the way.

The later model XJs have the belt routed where it is not in the way. However, on an earlier XJ like my 91 the belt interferes with getting the bolts started back in the housing. I previously wrote about changing a thermostat on a 99 XJ.

I popped off the radiator and heater hose. I disconnected the temperature sender wire.

I then removed the two 1/2 inch head bolts and popped the housing off the block. I set up a pan under the Jeep to catch the antifreeze. I also laid out newspaper to soak up the splatters as anti freeze is very slippery on the floor.

I cleaned up the bolts and the housing using the wire wheel on my bench grinder. I then use a scraper and a scotch brite wheel in my drill to clean the block face.

I noticed that the new thermostat did not have a bleed hole in it, so I drilled a small hole in the flange. It is hard to bleed all the air out of a 4.0 if there is no hole in the thermostat. Most of the ones I have bought lately have a hole but this one did not. So, I made one.

Getting the new thermostat to stay in the block while setting the housing is always tricky. I knocked mine out the first time and only noticed it when the antifreeze started to run out as I was filling the system.

I put a dab of Permatex on the flange to get the thermostat to hang in place long enough for me to slip the thermostat housing in place over it. I used additional Permatex to make the gasket stick to the housing. I held the housing in place with one hand while I started the bolts with the other hand. I was able to get it all in correctly on the second try.

I tightened the bolts and left the hoses off until I filled the system. I then reattached the hoses and filled the radiator completely with anti freeze. I then put back the temperature sender wire.

I put the belt back on and started the engine. I checked for leaks and made sure the engine came up to the proper temperature. I let it cool and topped off the radiator with coolant. I enjoyed having a nice warm heater again this morning.

Stant Superstat Super Premium Thermostat, 195 Degrees Fahrenheit – 45209

January 2, 2012January 11, 2012

Fabricating a Gas Tank Skid Plate for a Jeep Cherokee

The fuel tank on Jennifer’s XJ has taken quite a beating from off road driving. In fact the fuel pump pickup is no longer the lowest point in the tank making the effective size of the tank much smaller than its original 20 gallons. She will need a new tank to cure this problem but in the mean time, I decided to fabricate a skid plate to prevent further damage and to be ready when she can get a replacement tank.

I began by making a mock up out of foam construction board. The pieces I had had once been a sales display. It provided several large sheets of ¼” poster board with a foam liner. The material is stiff, lightweight and easy to cut and draw on.

I looked at several skid plates commercially available and I did not like the way they mounted. I wanted something that attached to the unibody frame rails one either side of the tank. Of all the ones I looked at, only the Mopar plate mounted like that.

I began with two pieces of 3x3x1/4 angle. I cut them to extend from the front of the trailer hitch to the front of the tank. I shaped the upper flange to match the shape or the curved frame rail section. I drilled holes in the angle face and then made corresponding holes in the Jeep. I tapped the sheet metal for 5/16 bolts. I used the existing exhaust hanger bolts on the passenger side as well.

Using the template I made from foam, I cut two side plates form 3/16 scrap. These extend the angle down to level with the lowest point on the tank. They are angle d at the rear so that I could mount a plate angled up behind the gas tank to protect the rear of the tank and not take away departure angle. I ended the rear late below the trailer hitch cross bar.

I then welded the extensions to the vertical parts of the mounting angle. I bolted the side pate to the Jeep temporarily and confirmed the measurements of the two main plates. I put one large plate under the main part of the tank and second plate going up at an angle at the rear of the tank. The fabricated angle between the two plates adds a lot of strength.

I tack welded the bottom plate to the side plates. I then took the assembly down and finished welding the bottom to the sides. I then welded the back plate to the assembly. I made a series of short welds along the long seam to avoid warping the metal.

Once the welds were finished I ground the edges smooth and painted it black.

Putting the entire assembly back up took some help as it was now too heavy to balance on one hand. Jennifer assisted me by balancing it on the under lift stand. She also helped move the exhaust pie out of the way while I started the bolts. Only one of the 5/16 – 18 bolts stripped in the thin frame rail. The others tightened down well. I drilled and tapped a new hole to replace the one that stripped.

I plan to replace the tapped holes with nut rivets in the future if these do not hold. The skid plate is very sturdy and neatens up the appearance of the rear of the Jeep. I think I will have to make another one for my Jeep now.

December 20, 2011

Hacking with Sugru

I have been reading about Sugru on several websites. I finally decided to order some and see what all the fuss is about.

I looked through the various bright colors and decided that black was really the only color I could see my self using for the projects I had in mind. It took some looking but I finally found where to order single color packs on the website. I entered my info and waited. My envelope arrived a few days alter and I was anxious to try out a packet.

I was at first surprised at how small the packets were. Somehow I had expected more volume for $15 but if it lives up to its reputation, it will be worth the price of admission.

For my first hack, as they call it, I decided to repair my broken key chain flash drive. It get s a lot of use and abuse and the case has been held together with tape for a while. More and more bits of plastic crumble off it each day. The exposed circuit board was beginning to worry me so it was an ideal test for my first Sugru hack.

I realized that about half a pack was all I was going to need for the repair. I did not want to waste the rest of the pack so I looked around for something else to test it on. I found a 2M radio that had an exposed wire at the power cord. Electrical tape keeps coming of the joint so I decided to try the Sugru.

For the thumb drive, I had to do a little prep work. The drive slips into a cover that is the key chain part. I needed to make sure the Sugru covered the damaged area but did not interfere with slipping it into the case. I read in the instructions that soap is a release agent. So I coated the case with dish soap and then molded the repair blob around the broken end of the drive. While it was still moldable, I slipped it into the cover. This made the Sugur form around the cover edge. I molded it in to the shape I wanted and let it set hoping it would really release for the cover.

The remaining Sugru, I molded into a blob around the wire side of the connector on the radio. I had a lot more confidence in this repair as I was able to work the putty between the wires and give it some mechanical grip as well as its adhesive powers.

After letting both tests set overnight I am pleased with the results in both cases. The thumb drive stuck a little in the cover but I was able to pull it out with a little force. It looks much better than the tape and exposed circuits. I think it is well protected now and should last a while.

The radio wire repair looks nice too. The joint is flexible and is much neater than having electrical tape wrapped around it. I am looking forward to hacking more things with Sugru.

December 5, 2011

Adding Shoulder Belts to the Rear Seat of an Early Jeep Cherokee

Shoulder straps were not available in the rear seat of a Jeep Cherokee until 1991. However the engineers who designed the body must have had them in mind from the beginning.

Scott decided to add shoulder straps to the rear seat of his 1989 Jeep Cherokee. He used belts from a 1993 donor. Removing the belts from the donor involved heating the under body nuts with a torch to allow the torx headed bolts to come loose. PB Blaster just did not loosen the rust and locktite enough to get them out with the limited torque of a torx bit.

After removing the interior panels, we found that the lower mounting points are all there in the exact same place as the 1993. The reel bolted right up and even the stabilizer tab hole is punched it the right place.

The slot that the belt passes through is there as well, however, we had to open up the front of the hole to allow the bolt to pass through without rubbing and to line up with the holes in the 1993 interior panels.

The anchor points at the roof were a bit of an oddity in this Jeep. On one side, the entire anchor point was welded in place but never tapped for threads. On the other side, the hole was punched in the sheet metal and the two plug weld holes were there, but the backing plate was not mounted.

For that side I fabricated a plate from ½ inch steel and tapped the appropriate hole in it. I also added a bolt hole to bolt it in where it would have originally been plug welded.

The mounting points under the seat are in a slightly different place than the 1993 donor. However, simply bolting the shoulder belts in where the original reels were mounted worked fine.

I was amazed that we only had to fabricate one plate and tap one hole to make this update. I really don’t understand why AMC did not offer rear shoulder belts in the early Jeeps since all the mounting points are there. Just for curiosity, we checked our 1984 parts car and found that it has the mounting points in it as well. So Jeep planned for shoulder straps all along but did not actually offer them until 1991.

Scott used the interior panels from the donor Jeep which matched the color of his older panels exactly. He had to cut two holes in the head liner to allow the roof bolts to go in but that was easy to do. He now has a nice safety update to his older XJ.