If this year’s game warrants a 2-cim shifter we will be considering AndyMark’s “Sonic Shifter”
I read some earlier posts (2014). It would be helpful to have recent thoughts from users on how this product has been for:
-ease of assembly/installation
-operation
-reliability over time
-use of encoder (which I understand comes pre-installed)
Thanks!
Are you locked into the idea of using the sonic shifter? Vex and West Coast products have options which are better than the sonic shifter in almost every way.
I do not believe this is accurate. There is an output shaft for an encoder, but I don’t think one comes included with the kit.
Beyond that, my 2cents when it comes to 2-speed gearboxes is to give VexPro a look. Their 2 CIM Ball Shifter (or even the 3 CIM Ball Shifter) is lighter than a Sonic Shifter, has a fully enclosed housing to prevent debris from getting into it, shifts more smoothly (in my opinion at least) than a dog gear due to the ball shifting mechanism, and will hold up through a whole season and beyond without any issues (if properly lubricated), and it’s fairly easy to use an encoder with. Oh, and VexPro gearboxes are also quite a bit cheaper than AM gearboxes.
I don’t have any particular problem with AM gearboxes, but when it comes to comparing two similarly functional and reliable products, lower weight and price always wins for me.
Would you mind listing what the differences between them are?
Let me remind you that the very team you’re mentoring this year had three, successive failures of the aluminum gears in the final reduction stage on three cim ball shifters. Including a pair of back to back failures that took us out of a one day offseason event we traveled 8 hours round trip for. I can assure you, based on that experience from 2014 we will NOT be using vexpro gear boxes in the drivetrain.
Both the WCP DS and the AM sonic shifter are dog-shifting style gearboxes.
An encoder can be fitted to the Sonic shifter out of the box, while a WCP DS does not, but a grayhill or CTRE mag encoder on an outer axle or a CIMcoder
In terms of weight the WCP DS, 2.92 Spread Kit with pinions weighs 1.93 lbs. The AM sonic shifter weighs 3.41 lbs with pinions.
The WCP DS is more compact than the Supershifter especially in terms of height.
There are 18 ratio options for the WCP DS. The Super shifter has 8 ratios options, but is capable of much lower gearing because of the inbuilt third stage. The WCP DS comes in a 3CIM version and the 3CIM is compatible with a PTO.
The WCP DS has 7075-T6 gears with teflon infused ceramic coating which is meant to improve efficiency.
Uses lithium grease for lubrication, not the fun red tacky grease as in the Sonic Shifter(because of lack of steel gears)
The Sonic Shifter can use a servo for shifting if required
The 2CIM WCP DS is $227.96 and the Super shifter is $279
We’ve used the sonic shifters quite a bit - we used two in our drivetrain and one powering our winch. We had a comp bot and a practice bot, so we had 6 in all.
We abused the one powering our winch to the extreme: we knew we were pushing it FAR beyond the design envelope with the forces were were shifting it under. We upsized the shifting cylinder and removed a stage so we could shift it into neutral. We routinely loaded with with 200-300 pounds and were releasing it.
We expected it to break, and it did. The shifting pin sheared and the dog gear rounded off the ears and the pocketed slots twice during the season.
The drivetrain shifters were installed and used as they were meant to be. The did not fail at all. In the off season we went in and had to change out the dog gears because the ears had rounded off.
We used encoders on them and had no issues.
Used as expected, we would recommend the gearbox to anyone.
Our history with the 3 cim ball shifter:
Hmm, we haven’t had any problems at all after 2 regionals and 2 offseasons with our 2014 bot and our 3 cims ball shifters.
That’s not what the Product Page says: Will be shipped with an am-3132 encoder pre-installed.
If you consider the included encoder, and the fact that the sonic shifter does ratios that require the 3rd stage on the ballshifter, the price difference is much smaller. $215 for the ball shifter + 40 for an encoder vs 279 for the Sonic Shifter. Weight does favor the ball shifter.
That looks really nasty, did you contact VEXpro.
I can see why your reluctant to use a ball shifter again
Three failures on different drive train sides isn’t a coincidence. We ran that drive train hard as you well know (Central Illinois 2014). It was geared aggressively and we used (honestly, inadvertently) down shift motor braking constantly because of our automatic shifting routine in our programming.
It is my belief, the reason for the failure is primarily related to the fact that the shafts that carry the final stage reduction are cantilevered. In looking at the damaged gears it was apparent the failure propagated across the gear teeth, which indicates angular misalignment. That angular misalignment also would have occurred during the periods where the gears were under the highest load.
I do believe that had that stage been steel gears they might have tolerated the abuse, but to me, the ability for the shaft to deflect and allow that angular misalignment is a design flaw. I believe there are a number of features that don’t promote a rigid configuration, but the cantilever is the largest problem.
We still use the drive train as a demo robot. We chose to modify the gearbox configuration to eliminate the cantilever and we haven’t see another incidence of the failure to date.
This is helpful, thank you. Any other comments from teams with field experience with Sonic Shifter would be helpful. (We are already familiar through direct experience with several options from other vendors) I appreciate the input.
What lubricant were you using and what was the overall reductions in your drive system (including wheel size)?
IMO our 2014 robot put it’s 3 CIM Ball shifters through far more abuse than the average team and the gears still look as good as new. For that matter, I’ve yet to see so much as a chipped tooth on any of the over 75 various Vex Pro gears we’ve used on competition robots in the past two years.
Good catch, not sure how I missed that, I did look at the page. Still getting used to the new AM site layout I guess. :rolleyes:
True the difference is smaller in certain configurations, but still less regardless, and Sonic Shifters doesn’t really offer anything the Ball Shifters don’t also (save a few gear ratios perhaps), so if you can still save some money and weight, why not?
Gear ratios were 18.75:1 and 7.08:1. Gearboxes were lubricated with moly grease containing Teflon. The gearbox direct drove a 6" x 2" wheel at the center of the robot which was chained to the other two wheel in the drive train side, also 6" x 2" wheels. All wheels were treaded with blue nitrile. Center direct drive shaft was supported with a bearing in the outer plate. Two other axles were dead shafts with bearings in the wheel.
The high load situation I believe created the problem was encountered when the driver returned the control stick to a neutral position with the robot at a high speed. The auto shifting code would have immediately tried to shift the robot to low gear with all three cim motors braking.
I’ve spent a fair amount of time “behind the glass” as it were. I’d challenge you to find a driver who pushed their robot harder and drove more aggressively.
I truly believe that we saw this failure because we pushed the design to its performance limit and shaft deflection leading to angular gear misalignment and ultimately gear tooth failure was the manifestion of that failure. If it had been on only one drive train side or it only happened one time I would write it off as bad luck, but that was not the case.
Sorry for the thread jack, here is my two cents.
My personal opinion regarding AM’s shifting products is that they are very robust and depending on your driving style worth the extra weight.
Steel gears are heavier, but stronger. This may not be warranted in some parts of a gear box where speeds are higher and torque is lower, but I believe it’s a nice feature in the final reduction stages where you see the highest dynamic loads and you’re transmitting the most torque.
In my FIRST career I’ve only had one type of failure from an AM dog style shifting gear box and that was due to mis-use It’s important to regulate the pressure available for shifting down to the stated spec because that will damage the linkage connecting the pneumatic piston to the shifter shaft. It would appear this issue has been mitigated with shorter throw cylinders at this point.
Winch mechanisms circa 2010 are an example of how much abuse the mechanism will take. Many users were disengaging dog gears with several hundred pounds of force in play.
In comparison, I do like ball lock style shifters, because there isn’t a force acting to disengage the shifter and shifting seems smoother to me.
These factors would drive the decision in my world.
Cost: Within 50 dollars of one another.
Safety factor: AM seems to have higher safety factors while VP designs are lower.
Weight: AM gearboxes are heavier while VP designs seem to be lighter.
I have my horror story. I’ve done a thorough analysis of why that happened and I’m confident in my understanding. Do I think most teams would encounter the same issue? No.
Also, I have some inherent bias. I have a number of good friends who are a part of Andymark, so no doubt it feels good to spend money there.
Ultimately you’ve got to use whatever gives your team the competitive advantage and fits your need.
Please implement automatic shifting regardless of which transmission you use. With the worry of brown-out and observations during 2014 with people blowing 120 amp breakers I think it’s a must. Drivers generally don’t use manual shifting when they should. It’s hard to teach and takes a ton of experience to learn to use without hesitation. Ultimately in an intensive enough competition situation they will forget.
We used 4 of them on our 2014 robot in a Mechanum setup. We haven’t had any problems with them in 2 district events, district champs, 4 offseason competitions and a handful of demos. We haven’t checked them for signs of wear but there are no signs of them breaking or showing age.
I want to point out for folks who don’t spend a lot of time looking at gearboxes that this is a very aggressive gearing with one of the highest CoF wheel tread materials. My quick calcs say this generates ~747 pounds of force at the wheel patch with 6 CIMs, well over the traction limit of 185 for a maximum weight robot in 2014. Meaning it is an extreme case and may not be the best one to guide the decision of an average team.
Overall this is great feedback. I have been wondering how the 3rd stage on the 3 CIM works at high loads. I always thought the sheet metal with standoffs 3rd stage looked a bit rickety. I am curious if you ever subbed out the 7075 aluminum gears for 4140 steel gears in the third stage of the 3-CIM shifter? Sounds like it was a misalignment issue more than a material strength issue. Did you ever try stacking on a second Vex third-stage plate to add stiffness to the third stage bearing? This would pickup more of the bearing race and possibly prevent angular deflection.
I am assuming the output of the gearbox was direct driving your center wheel in a tank drive. How do you think a 2 stage 3-CIM shifter would work if offset from the wheel axles and with a #35 chain reduction between the gearbox and wheel axles in lieu of the Vex 3rd stage?
Was there a particular reason for adding this “stop on a dime” feature? Did it work as you had hoped? Would you recommend it? It does seem like a recipe for gear teeth shearing.
Based on photos and gearing - I agree - you win!
-matto-
I second this.
Though that said, we used the same gearbox in 2014 with a 26.04:1 low gear and a 7.08:1 high gear on 4" wheels with the same tread. :rolleyes:
I don’t think the issue is the plate stiffness, but the fact that the small output gear (the one with the missing teeth in the photo on the last page) is on a cantilevered shaft. If one was to modify the plate so that another bearing could be used on this shaft, there likely would not be any problem.
On a related note, our team actually did this recently with a pair of VexPro 2 CIM Ball Shifters that we had inadvertently ordered without the 3rd stage (and apparently the output shafts on the 2nd stage are longer when order it like this). So we made a pair of replacement plates so that the smaller 3rd stage gear could be retained by an additional bearing instead of having to remove the shaft and lathe a snap ring channel into it.
Wow I had never noticed that the output gear is unsupported on the 3rd stage for both the 2-CIM and 3-CIM ball shifter. For the 3-CIM I saw the hole in the plate and assumed it was 1.125, but it is only 1.000. Perhaps Vex thought the extra bearing would over constrain the shaft? A rare miss by Vex. The being said, the gear separation is 84T, so you could add some of my new favorite part, the Face Bearing Mount.
I am curious if you mounted your wheel right the to the output shaft or if the shaft was supported? I would take the 3rd stage output shaft and put two chain sprockets on in, then pass it thru a VersaBlock and put the wheel on the other side of the tube for a WCD setup.
The more you learn …
