Flawed Designs

Designing a Drive Shower isn’t as simple as it might seem: "Beware of the White Salmon Salesmen" Based on the fact that Simrek’s Summit Design Drive Shower is now the most copied drive shower on the market, (at least five copies that we know of), and their Halo Design is the best selling drive cooler on the market, we will be focusing the attention on that type of design. It’s referred to as a dual sided ridged tube design. - Besides getting maximum cooling of the drive oil inside the drive, a drive shower needs to not only process the water but also the debris normally found in the water. It has to stand up to the massive amounts of vibration caused by the stern drive, and it also needs to keep its shape and pick-up port location consistent. They also need to continue working at any trim angle. To get all these requirements to come together in one design takes more than a couple of yahoos with a tubing bender. - Consider these drive showers as a huge tuning fork. An example of a tuning fork is the metal thing that the doctor bangs on and then touches near the back of your ear to test your hearing. Only this tuning fork is three feet long (6 feet of tubing formed into a “U” shape). The same thing that causes the buzzing sound in your ear is the vibration that is constantly running up and down the tubing of the drive shower, only at a much greater rate and non stop. The term for this vibration is harmonics. If left unchecked, what it will do to ½ inch diameter tubing is amazing. It forms a crack in the tube that look as if someone ripped it apart like a piece of paper. Harmonics is by far the biggest hurtle to overcome while designing a solid tub drive shower system. We are not seeing any consideration for the harmonics in any of the Summit knock-offs that we’ve seen. Gimmicks like: adjustable length pick-up ports, mounting the shower without drilling holes in the cavitation plate, adding extra dump ports, or slotting the dump ports, will only help to promote the destruction of the shower through the harmonics. If the fit of the shower is at all loose and the harmonics are not properly grounded, every hole, edge and corner, will become a starting point for a crack. You really do need to know a lot about Physics to design a shower that will not only work, but last. - After looking at the Summit and its many knock-offs, we determined that it’s best to… * HAVE ONLY ONE MOUNTING BRACKET: - First, one 3/8 bolt is more than enough to secure the shower. If you used two, you would have to remove two bolts from the bearing cap. That equates to removing 50% of the bolts that secure the cap and the oil seal. Knowing that one bolt is enough, and that it is better to disturb those seals as little as possible, we would conclude that two mounting brackets will probably cause more oil seal problems than it is worth. ** MINIMIZE THE NUMBER OF HOLES WHILE MAINTAINING MAXIMUM COOLING: - If seven dump ports are good that 14 should be better, right? There is a condition in Physics referred to as, The Law of Diminishing Returns”. Think of it like this; if one bucket of water puts out the camp fire, how much good would it be to dump on a second. During the testing of Simrek’s Summit, we found that we only picked up an additional 2 degrees of cooling by adding an 8th dump port and the 9th, was less than one. Knowing that the more holes that you put in the tubing the more susceptible it becomes to cracking; we would recommend minimizing the defects even though it would mean giving up 2 or 3 degrees of cooling. *** CONSIDER THE EFFECTS THAT THE DEBRIS IN THE WATER WILL HAVE ON THE SYSTEM: - Designs that: reduce the size of their dump-ports to make them work more like a nozzle or jet, or that use slots instead of holes to create a fanning effect, are not considering the effect that algae and other forms of debris will have on their systems. There must be some form of a filtering system associated with a drive cooler if it is to remain truly efficient and maintenance free. One of the biggest problems plaguing any water cooling system from boat engines to nuclear reactors in fresh water is the Zebra Muscle. Any cooling system that is vulnerable to being clogged with zebra muscles should be avoided at any cost. With the race to find an alternative to Simrek’s patented 90 degree port system, manufacturers have been coming up with all kinds of gimmicks and variations of the design. Some of them even claim to be improvements. One advantage to the Simrek pick-up and dump port configuration is that debris like twigs or stems can’t make the 90 degree turn they would need to make in order to get past the pick-up ports. Also, anything that can get past the pin (which divides the pick-up port in half) can get past the bends and out the dump ports, even Zebra Mussels. So their system will not get plugged with debris. - One of the recent entries into the drive shower market with yet another copy of the Summit except they uses a pick-up port with a 45 degree angled surface for the bottom/back of the port, instead of the horizontal plug and straight tube that Simrek uses. This design should produce an increase in the water volumes but it will come with one huge draw back. Without any form of a filter and a smoother path for not only the water but also for the debris to follow, this system will cause an increase in the amount of debris that will get caught up in the upper portion of the shower. Long soft items, like twigs, stems, tree bark and even something like a drinking straws flexible enough to follow the 45 degree angle and lodge itself so far up the tub that you wouldn’t be able to get it out The same debris build up problem occurs in other manufactures designs referred to as “the 80 Degree Ports or the “Ice Cream Scoop Ports. **** AVOID THE USE OF ADJUSTABLE LENGTH PICK-UP PORTS WHENEVER POSSIBLE: - The length of the pick-up ports is critical. 3/8th of an inch too short and they don’t penetrate the layer of foam found under the anticavitation plate and they will supply a minimal amount of water. 3/8th of an inch too long and they will cause the propeller to cavitate. Manufacturers that offer an adjustable length pick-up ports are counting on you to determine the best length for their pick-up ports. They are asking their customers to hang over the back of their boats at 30 + MPH to see if the shower is working. We do not recommend that you do that. ***** MOUNT THE SHOWER USING HOLES DRILLED THROUGH THE CAVITATION PLATE: - No one wants to put extra holes in to their boats, and we understand that. The problem is that different boat styles can produce speeds in access of 100 MPH. The amount of shearing force that the pick-up ports are exposed to is more than enough to bend the ½ inch diameter tube if it is not supported as close to the water as possible. The only existing component on a stern drive that is capable of handling that much shear force is the threaded shaft that attaches the lift rams to the drive. The problem that still exists is; the location of the end of the lift rams with respect to the end of the drive is far too great a distance to expect the ½ diameter tube to hold its shape with the force of the water being too great at higher speeds. It will simply flex up and away from the force of the water. If the force is nominal, (a slower boat speed) the tube may return to its original shape, but if the force is too great, it could deform the tube permanently. Knowing that the location of the pick-up ports is critical to the efficiency of the system, and without a substantial support system for the tubing, we have found that the only system that will function properly is a system that penetrates, or utilizes a well designed anchoring system to attach itself to, the anti cavitation plate. ******VERIFY THAT THE QUALITY OF THE MATERIAL BEING USED IS HIGH ENOUGH TO HANDEL THE STRESS BEING PUT ON IT: - Stainless steel tubing can be manufactured in a variety of ways and all of them have a cost associated with it. Rolled/welded tubing will cost about 40% less than extruded tubing, often refereed to as seamless tubing. Rolled/welded tubing may not stand up to the vibrations normally found in any stern drive, and eventually those welds will crack. Also, rolled/welded tubing needs to be polished to remove the burn marks left from the welding process. A polished finish may look nice, but it might also mean that the shower won’t last very long. - There are also many different kinds of stainless steels, and not all of them are completely corrosion resistant. One way to determine the quality of the stainless steel (without being a metallurgist) is to understand that the more pure the stainless steel is, the more resistant it is to accepting a coating or coloring. For that reason, you should be wary of manufacturers that offer their showers in various colors. If the coating comes off, corrosion will not be far behind. A WARNING ABOUT MANUFACTURERS CLAIMS AND THEIR TEST RESULTS: - We have found that it often works best if you do not take the word of anyone doing their own testing. With no means of verification, it is too easy to fudge the numbers, especially if they have a vested interest in the outcome. Even if their intent is to be honest, it is way too tempting to say “well the gage was sort of close to the 260 degree mark and if we would have been going just a little faster, or had more drag on the boat, etc”... Credible testing can only be done by independent testing facilities and repeated with the same results by other independent testing facilities. Here is an example: You are responding to an ad for a minivan. The owner claims that it can do 0 to 60 in 2.5 seconds, and that he’s got test results to prove it. It would be one thing if he could produce NHRA time slips to back up his claims, but its probably not going to take you long to figure out that it was just he and his buddy with a wrist watch, and they are both willing to swear to these results.