Project BMP

Page 7


Starting to look like a buggy

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I didn't get to work on the rig on Saturday, but Sunday was a very productive day.  With the help of my friend Scott, we were able to knock out all the tubes in the upper structure that had a bend in them.

I have learned a few helpful things about bending tube this go around and would like to pass them along. These tips involving "fixing" a tube that you may have over bent or slightly under bent, being just a degree off can really throw the design off if the tube is a long one.  The first thing to keep in mind is that you will never get all your angles perfect.  The first few tubes I bent on my old rig were very frustrating because I was going for perfect angles.  Once I accepted the fact that they would rarely be right on, things were much easier and less stressful.  One of the big reasons it is hard to nail the angles is that the steel tubing has a certain amount of spring back.  This means you have to actually over bend it to get to the angle you want. The amount of over bend required varies and goes up the tighter the bend.  This means a 15 degree bend may only require you to go 3 degrees past your target bend angle while a 95 degree bend could require you to go 10 degrees past your target angle to achieve the desired bend.   The material thickness also affects how much spring back the tubing will have.  What this all means is you will be able to get within +/- a degree of the desired angle pretty easily.  this may cause the tube to not fit where it is supposed to, here's the solutions:

If you haven't bent it far enough you have two options.  The first and easiest is to put it back in the bender.  The second option is to use a ratchet strap to pull the tube inward (shape permitting).  The ratchet strap option is really useful when trying to get a hoop to line up on both ends with an existing structure.

If you have over bent the tube you need to unbend it.  You will need a place to wedge one end of the tube that is anchored solid.  A receiver hitch on your tow rig, the stake pockets on a trailer or even the rim of a derelict parts car work well.  You then stick one end of the tube into the anchor, slide a 6-12" long piece of sleeve tubing into tube to be bent leaving half of it sticking out the end. Next, slide another, longer tube over the exposed end of the sleeve tube.  Now your are ready to unbend.  Grab your lever and pull in the direction you need to open up the angle.  Keep in mind you will have to bend past where you want as the tube will spring back after your pull.  I usually just give it a couple big pulls and then take it back to the buggy to check the fit, repeat as needed.

Next up is some cross bracing.

Rear view.

Cost Update

One of my goals in this project was to keep the money pit under control.  So far so good.  To date I have sold approximately $5,600  worth of parts off of my old rig and the parts truck with another $2,100 in parts to go.

As you can see in the picture above, my expenditures have totaled approximately $5,400 (taxes and shipping included) at this point and my to be purchased list is rapidly shrinking.  $680 of that total was for tools and consumables used in the buildup, the tubing for the project ran $987, and the misc. steel and various brackets have come to $147 so far. I did manage to get a bunch of large steel plates free with the tubing purchase so the material cost could have been higher. You will notice some of the prices I paid were very good, this was made possible by several group buys with the BTG Rockcrawlers.  I guess it was just good timing on my part or luck that several of us started major build ups at the same time.  The parts without a price I am considering free because I pulled them from my parts truck and managed to make the purchase price of the truck by selling the remaining parts.  The total would be close to a $1000 higher if I would have had to purchase those components.

I am also tracking my time.  To date I have 113 hours into the design, 125 into the build, and 46 hours of tear down time (parts truck and old rig).  The design time is kind of high due to me going back in and trying all sorts of different configurations, one of the advantages of modeling the buggy before building it.

Some of the tabs I have been working on (lower section of the picture).  The shiny stuff in the upper section were all bare steel parts now nickel plated (hydro cylinder mounts, shifter cover, steering arms and misalignment washers).

I ordered a bunch of electrical parts from Del City for the main wiring harness and they arrived today. The plan is to clean up the main wiring harness and make it look really nice. I bought some shrink tubing, some colored wire wrap, new relays w/ wire harnesses, a power distribution block and some fuse blocks.  Unfortunately the blade style circuit breakers I bought don't fit in the fuse boxes (too tall).

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