Tag Archives: fabrication issues

What I was thinking about last night

I have this “problem” with thinking, especially when I’m trying to sleep. This is especially true when I have a niggling design/fabrication issue that won’t let me go until I solve it.

The issue that kept waking me up last night was there will be zero clearance for the oil and transmission pans when the belly pan is installed on the Sprint-T. That also means there will be zero clearance for the drain plugs with the belly pan is installed.

Since the Sprint-T is going to be raced frequently this is a serious problem because racing requires frequent fluid changes to maintain the performance of the drive train, especially since it will be driven to and from the races. Now transmission fluid is not as critical as engine oil, but it will still need to be changed during the racing season and at the beginning of the season. Cars that are not raced then driven on the streets or highways can usually go their entire lives without a transmission fluid change, but even street only engines need oil changes regularly because oil doesn’t last forever and oil filters don’t catch all the contaminants that get into engine oil. And race engines usually get fresh oil every race meet, sometimes during the race meet if there is a lot of dust and dirt in the air, even if the engine is using an air filter on every engine orifice exposed to atmosphere.

Now there are two problems to be solved here, the first is since transmissions don’t normally get fluid changes they don’t have drain plugs, and the second is having drain plugs that are flush with the bottom of the pan but still drain completely dry with a tolerance for cling to the sides and bottom. The solution is to install the drain on an edge with the hole being flush to the inside bottom surface of the pan, and to contour that surface to direct the draining fluid to the hole. This is obviously easier on a pan that is being fabricated from scratch, but since the vast majority of transmission pans are stamped out of thin sheet metal it can be accomplished with a little hammer and dolly work, or a ball peen hammer and a soft 2 by 4.

The first thing to do is decide where the drain is going to be, and then “massage” the bottom of the pan with the hammer and whatever you choose to back it up to make that the lowest place in the pan so the fluids accumulate there. Then drill your drain hole flush with the bottom through the side of the pan. That’s the easy part, the hard part is making a plug that doesn’t hang below the bottom of the pan.

The next step is to pick a bolt that will fit the hole you drilled, ideally that will fit snugly in said hole because it will be used to locate the part that holds it to the pan. This is going to be a nut that is compatible with being welded to the pan. You will thread the nut over the bolt you chose as the plug, then stick the bolt through the hole in the side of the pan and rest it against the bottom of the pan with the nut flat against the side of the pan, and tack weld the nut in place so you can let go of the bolt. Finish weld the nut and make sure you can thread the bolt in and out of the pan. Then comes the part that lets the pan sit flat against the bellypan of the car. Using a cutoff wheel against the bottom of the oil or transmission pan slice off the part of the bolt and nut that stick out past the bottom surface of the pan. Just for insurance you might want to run an extra bead of weld on the part of the nut that was cut where it joins the pan if there is no weld showing, to prevent seepage. Then grind the weld flush with the bottom of the pan.

Now the design of the pan for the engine oil is going to be a little tricky, since it is two pieces that bolt together on the engine and the drain will have to somehow not interfere with the function of the bottom flange that holds the bottom of the pan after the pan is bolted to the bottom of the engine, since the bolts that hold the pan to the engine are inside the oil pan when it is installed. Somehow I have to get the bottom of the nut flush and the bolt resting against the inside of the pan, with the bottom being bolted to a flange around the bottom. Or I can move that flange to the top, the part that bolts against the engine, and do the drill the hole in the side routine like it was a regular oil pan that bolted up from the outside of the engine. The bottom will have to be built like a regular oil pan instead of just a flat plate that bolts to the bottom of the pan. Still easier than welding tubes for access to the bolts that hold the pan to the block on a pan with huge kick-outs to give the engine oil room to be flung from the crankshaft. There was an episode of Engine Masters that used a pan that had the mounting bolts on the inside and that pan actually made more horsepower than a deep sump pan without kick-outs but was way deeper than the pan with the kick-outs. I would link to it but unless you have a subscription to Motor Trend On-Demand you won’t be able to see it.

So anyway, that’s the kind of stuff that sometimes keeps me awake at night, or haunts my dreams (yes I have dreams of making car parts, and no I don’t know what that means if anything). Happy Fourth of July to those who celebrate it.