Daniel, I will be in Liechtenstein 17-22 June so will stop by to see you and Jürg again on 16 June. Will chat on e-mail.
Please Read!!! Very Important!!! I have to say, this sentence has been on my mind ever since I first read it! Tonight I decided to dis-assemble my SD75i once more to perform this task. I wondered if it would improve the speed any from what I was able to tweek already! Before dis-assembly, I warmed the SD up and compared speeds with my fastest GP35. Slow, very slow. Don't even think about my Dash 9's with it. They are way faster than my GP35's. Dis-assembled it. Removed the inner 2 black squares including the brass bearing. I wiped off what seamed to be a light grease. I re-assembled the Chassis. I placed it on the track and now the SD75i is faster than my fastest GP35 and slowest Dash 9. It zips around the track maintaining a constant speed with my second fastest Dash 9 now! Talk about speed!!!!! You've got to try this!!!! Slow Poke No More!!! Hobo Tim
AND YOU DIDN'T TAKE PICTURES? I would like to see wich parts I need remove. I am more of a visual person.
I told you! I told you all a long time ago! The motor draws 20ma free spinning outside of the mechanism, and 100ma stalled. When you get the current draw down as low as 40-50ma, the loco will be running as fast as a GP35. When your current draw is up above 65-70ma, you loco will crawl. The key is to reduce friction! I sanded the bearing blocks down, balanced the worm/silicon tubing so the sorm don't rub either of the brass BB bearings, and avoided pinching the frame too tight while piutting the shell back on, and I have 2 that scream!
-----Number One of Three----- Ok, ok, here you go!!!! Photos tell all!!! This is of course the much talked about AZL SD70 Locomotive! This one belongs to Jeffrey White. At top speed, it moves about half the speed of an MTL GP35, and that is after tweeking the inner drive shafts already. This morning I decided to dis-assemble this loco and perform the same surgery that I performed on my SD75i BNSF last night. The following two posts show photos of the inside and of what I removed! Hobo Tim Disclaimer: I am posting these photos of what I did to modify my own and a friends (who gave me his permission) AZL SD70/75i Locomotives. If you attempt to modify your own SD70/75's, you are taking this task upon yourself. If you mess something up it is your own damn fault so don't try to place any such blame on me. :teeth:
------Number Two of Three----- Ok, here is the shell off of the chassis. Next photo shows the clip location of one of the fuel tank clips. Remove the PC Board from the chassis. The short LED is front of the locomotive. Next, carefully un-clip the ends of the fuel tank. Only apply enough prying force to unclip it. Do this to both sides before trying to remove the fuel tank halves. Hobo Tim
-----Number Three of Three----- This photo shows the chassis opened up with the motor, shafts and worm gears. Notice the black plastic pieces on the left side. This is what both sides look like before I modified anything. This shows a close up of the left end. You want to remove the motor from the chassis. Do this carefully. Inside of the black plastic piece is a brass gimble bearing. Carefully remove the worm/shaft from the motor. Make sure the clear rubber connecting tube stays on the motor shaft. Slide the inner black plastic piece and the brass gimble bearing off of the shaft. I then cleaned the shaft. Re-install the worm/shaft into the clear rubber connecting tubing. Perform the same removal from both sides and carefully re-assemble the outer worm/shafts inside of the outer black plastic piece and gimble bearing. This is what it should look like when finished. Make sure that both worm/shaft ends are loosly fit inside of the outer gimble bearings. If the shaft is applying pressure against the gimble bearing the speed will great affected. Loose shafts. Also, before assembling the chassis, make sure the clear connecting tubing is aligned. Hold the motor and turn the motor brass drive weights to make sure the clear tubing is aligned. you'll see what I am talking about!!!! Put the chassis back together. Put the two Top Clips onto the chassis top. Insert the two trucks into the chassis. Traction truck in the back. Once the trucks are in the chassis, carefully assemble the fule tank halves. Clip them together. Then put the PC Board on the top of the chassis. Next, test the loco on the tracks. It should run smooth and fast!!!! It is possible to tweek the worm/shaft from between the chassis halves now without taking them apart. Use a small jewelers screw driver, a hobby knife, of a pointy end tweezers to adjust the shaft. Easy done than said, or at least typed. What makes typing the procedure so difficult is not knowing the names of all the parts! Questions??? Hobo Tim
Tim, Another thought, have you tried removing the outer plastic piece and leaving the inner one in place. This might keep the plastic connecting sleve in place better and also keep the wobble down when loaded. Kim
Wery informative!!! I think i might get some of this engines WHEN they release SP Bloody nose sheme. ON my new layout i will run both modern and "old" trains
WOO HOO! thanks. this is like a famous mod done on N scale (Atlas type) locos, but in that case it was to reduce noise. this is also my first close look at the innards of the SD70 mechanisms. very well done, photographed, and catalogued. you've done us all a service, tim. thanks. dave f.
IF! Kim, You do have a point!!! I have yet to apply any loads to the newly modified SD's, but, if you look at what Daniele posted earlier, he is now able to pull 51 of MTL's rollingstock. I am guessing this is boxcars, flats, tank cars, and gondola's. I usually run Intermodal so my circumstances are different. But, it is possible that any wobble would not affect performance. Your suggestion of removing the outer plactic piece and gimbal bearing and leaving the inner is an idea if ever I have problems with the current modification. After having modified that Union Pacific SD loco, it runs faster than my BNSF SD and almost as fast as my fastest Dash 9. My Dash 9 goes around the 195mm curves smoother than Jeffrey's UP SD, other than that slow down, the SD would maintain same constant speed as my fastest Dash 9. Can't get my BNSF SD to go that fast. Jealous now!!! Just Wrong!! Ok, look forward to any and all messages where people want to or have modified their SD locos. Hobo Tim
Tim, thank you for the explanation with pictures, very well done!! yes, the 51 cars were mostly boxcars and tankers, because they are shorter than cylindrical hoppers and intermodal cars, and my test layout had only the length of 4 metres. When modifying my SD70 I first read Robert's post on this topic (thanks for your experiments with amps!) and tried to sand those black blocs down. result was not so convincing in my opinion, so I tried with taking the outer two blocs out, which resulted in wobbling and hobbling of the worm gear and even caused an electrical shortcut (between the chassis half-shells) which cost me the PCB lightboard (for which I got replace parts from AZL). so I came to the solution to take out the inner two blocs. this is also better for the worm gear and results in pulling force because: an axle spinning freely causes damage to holders and provocates loosening and even breaking of the components as there are fly forces. with the outer blocs holding the worm gear in position, there will be no damage to-, loosening and even breaking components. greetings, daniel
thanks daniel for being the grand experimenter. this is the kind of thing that helps us all. way to go. dave f.
At first, I was sure that most all of the speed reduction was due to binding on the ball-gimble bearings, as the black plastic was sooo tight in the chassis that it was also squeezing down on the brass bearing. This put a misalignment bind on the shaft. Even the the "ball bearing" has friction to the shaft, it can freely spin in the plastic, if it is not tightly captured. Removing it is one way to solve it but could lead to some slop in the worm gear under load. Rob Ray was one of the first to mod his. He ground out the casings, I filed my blocks down. His REALLY goes fast, mine only improved. His was a bit noisey. I had originally only filed my blocks down conservatively. I need to file mine down some more. Mine were not flat-square. The edges (sides) were tapered, the block was itself square. I simply filed the edges flat. I think I need to take more of the outer dimensions off so it fits looser in the housing. Even the the "ball bearing" has friction to the shaft, it can freely spin in the plastic if it is not tightly captured. I was just waiting on DCC before I opened it up again
Ok, it was a minor miracle, but I was able to take off the fuel tanks without breaking them. I used a chisel blade rather then a jewerler screw driver. My purpose for taking them off is not to increase the speed. My purpose was to improve its pulling power going forward. I took off the trucks with the intent of switching the axles from the front to the back, but taking the axles without breaking them look like a dauting task. Then it hit me. Move the front truck to the back, and move the back truck to the front. Well, my theory was correct. Now it pulls without the wheel slip. Based on my experiment, my suggestion to AZL is to put the traction tires in the back of the trucks.
Not quite sure about this old post. Many of us now have numerous SD-7x's and typically pull 20-30 cars of varied makes each show. I often pull heavy MTL Gunderson's or AZL Hoppers, both will test your loco. The MTL GP's & SD40 also pull these with no problems. After almost 2 years of running, no tweaks necessary. .
I flawlessly run a 20-car train (including heavy cars, such as FR Models 60' woodship gondolas) on my 3% grades with a pair of SD70... No wheel spinning at all. Dom
I would have to say, that this thread is still very relevant, I don't know if the new SD75i AZL loco are still delivered with what looks like 2 brass compression sleeves inside a square plastic fitting on each side of the motor, but mine had great issues running well, so following this thread and taking the inner ones out had really improves the running, I just did it last night on one of my SD75i. Afterward my loco was still not running well, it was still jerking at slow speed, but that's when I've found plastic flash on the front plastic truck blocking the free rotation of the gears, once the flash was cut out, the loco was running at a great speed at 8 volts. (this last problem was not relevant to this thread thought, but maybe others had seen this flash problem in the trucks) Thanks to all the developers who brought this solution. :thumbs_up::thumbs_up: Ben
