VEXPro 2014 Product Initial Impressions

[magnets]

You’ll find that’s the case for most dog shifting gearboxes you can buy. I would assume it just makes the whole setup more tolerant inaccurate cylinder placement. Although I’d be curious to hear what the reasoning is from vex.

The total width of the vex slot is 0.821 inches. AndyMark uses 0.48", which in my opinion is reasonable. We’ve used 0.275" in the past. Vex’s ball shifter requires perfect cylinder alignment, but it works because they have a nifty coupling, the same that’s used here.

The three CIM DS gearbox confuses me. There is 1.316" between the plate and the gear closest to the plate, and there is nothing in this space. I understand why this room is useful if you’re looking to add a PTO with a pulley, but I don’t see why that extra space is there in the normal model. The could probably sell spacers that are 1.25" shorter, and have shorter shafts.

[AdamHeard]

The total width of the vex slot is 0.821 inches. AndyMark uses 0.48", which in my opinion is reasonable. We’ve used 0.275" in the past. Vex’s ball shifter requires perfect cylinder alignment, but it works because they have a nifty coupling, the same that’s used here.

The three CIM DS gearbox confuses me. There is 1.316" between the plate and the gear closest to the plate, and there is nothing in this space. I understand why this room is useful if you’re looking to add a PTO with a pulley, but I don’t see why that extra space is there in the normal model. The could probably sell spacers that are 1.25" shorter, and have shorter shafts.

Sprockets go in that gap (for a WCD team).

There are valid reasons for all the points you’re raising, and your assumption that because you do not immediately understand them they must be silly/wrong is unfair.

[Cory]

Now that I’ve stopped in with a team that has some more vex parts, I thought I’d post my opinions.

There are two parts that I’m not a big fan of, and these are the 40 tooth dog gear, and some of the pinions. The bearings (which come pressed/locktited into the gear) stick out the end, which is a little weird. Once you pop the bearing out to replace it with one that actually fits, you’ll notice that the hole is oversize, and you’ll need to get some locktite. The dog pockets are also way bigger than they need to be. It would also be nice to see fillets on the 40 tooth gear like there are on the 44. I don’t have a vex dog with me, but the CAD model shows no fillets there either, unlike the AM ones. We’ve found that these fillets make a lot of difference. Those right angles are huge places for stress to concentrate.

These are all super trivial complaints and have no bearing on the functionality of the product. Why would you expect anything other than the bearing that is currently in the gear to fit perfectly (for the record, we loctite every bearing we press)? Why would you want the dog pockets smaller? What if you were going to use this gear for a larger gearbox, say to disengage a winch? Would you want a larger dog?

Have you really seen a dog fail because the teeth didn’t have radiused corners? I haven’t. The weakest portion of a dog is the threaded hole. If anything the corner that you want radiused is at the base of the tooth, not the vertical edges. We have run unradiused edge dogs with zero issue.

Perhaps you should consider applying to VEX and then you can design their products?

[drwisley]

These are all super trivial complaints and have no bearing on the functionality of the product. Why would you expect anything other than the bearing that is currently in the gear to fit perfectly (for the record, we loctite every bearing we press)?

How much clearance do you run for a 1.125 flanged bearing? Did this change with the loctite? I seem to recall you using some small fasteners to retain bearings as well. Any insight would be appreciated.

[magnets]

Sprockets go in that gap (for a WCD team).

There are valid reasons for all the points you’re raising, and your assumption that because you do not immediately understand them they must be silly/wrong is unfair.

You’re right. These vex people are pretty darn smart, and I’m not saying I think their designs are silly, I just don’t understand them. So, I’ve reworded my thoughts as questions.

1.) We are doing a drive system where the wheels are driven, by chains, so that the sprockets run through the gearbox. We are using #25 chain and we have about 0.75" extra room. I think the extra space is for a team who wants to use a WCD with two 15 mm belts, as the space is slightly bigger than 30 mm.

2.) Why is the shifting slot longer than the travel of the cylinder? Does anybody know the advantage to having this be around 2x longer than a traditional setup?

3.) The traditional dog gear enters into the gear 0.125", so that you can have a 0.125" pocket in a 0.375" gear while keeping 0.25" remaining for a normal sized bearing. The vex dog gear has the bearing sticking out the back a little bit so that there is more engagement between the dog and the gear. When doing this, you loose the advantage of having the flange on the bearing. Does anybody know why this is?

4.) Why aren’t there fillets on the dog/dog gear? I’m not talking about the ones on the outline of the dog pocket, but between the face of the gear and the vertical face of the pocket. A while ago, I made some of these dogs out of steel. Switching to a ball nose endmill and getting even a small radius on all the corners fixed our shattering dog problem.

[magnets]

These are all super trivial complaints and have no bearing on the functionality of the product.

Yes, they do. Having to remove the plate to remove a shaft to remove a CIM motor is a little silly, just because the retaining ring is a little big, but I don’t really see how this can be fixed.

Why would you expect anything other than the bearing that is currently in the gear to fit perfectly (for the record, we loctite every bearing we press)?

Because it’s advertised with a 1.125" bearing bore, not with a hex bearing pressed in with locktite. And besides, having a flanged bearing with the flange just sitting out in the middle of nowhere isn’t “fitting perfectly” to begin with.
When we bought our gear, it said nowhere that a bearing would come with it. I’m not complaining about our free hex bearing, but we planned on putting a not-hex bearing in the gear.
Normally we use 1.1245 holes, because at that size, there isn’t much slop in the fit. The vex bearing bore on one gear was 1.13.

Have you really seen a dog fail because the teeth didn’t have radiused corners? I haven’t. The weakest portion of a dog is the threaded hole. If anything the corner that you want radiused is at the base of the tooth, not the vertical edges. We have run unradiused edge dogs with zero issue.

I’m not sure my first post was clear. I’m talking about a radius between the horizontal surface of the dog, and the vertical surface used to transfer torque to the gear.

Yes, our kicker in 2010. The problem went away after using a ball nose endmill.

Do you really use an endmill with no radius to cut your dog gears?

Again-I think vex products are among the best we’ve seen from an FRC supplier, but I’m just curious as to why some parts are the way they are.

[Alex_Cormier]

I am slightly disappointed in the 6" mecanums. We bought a set in hopes to get the better traction then the AM ones. But within only 2 hours of driving and testing, we have numerous rollers that the axle/pin have come very loose. The Return On Investment of these wheels are horrible. We have since switched over to a set from AM, but have lost 4 lbs in the process of doing so.

[Paul_Copioli]

I am slightly disappointed in the 6" mecanums. We bought a set in hopes to get the better traction then the AM ones. But within only 2 hours of driving and testing, we have numerous rollers that the axle/pin have come very loose. The Return On Investment of these wheels are horrible. We have since switched over to a set from AM, but have lost 4 lbs in the process of doing so.

I can tell you with certainty that is not normal. Something is wrong. Please contact VEX support and we can get you straightened out.

[tim-tim]

I can tell you with certainty that is not normal. Something is wrong. Please contact VEX support and we can get you straightened out.

Paul, we noticed the same thing on both of our robots. We kind of shrugged it off to how the wheels “wear in”, as it is our first time using the VEXpro Mecanums. For us, I would say it was more like majority of the rollers felt extremely loose.

We haven’t noticed any performance issues; but now concerned with the reliability of the wheels if you are saying this isn’t normal.

[Paul_Copioli]

Paul, we noticed the same thing on both of our robots. We kind of shrugged it off to how the wheels “wear in”, as it is our first time using the VEXpro Mecanums. For us, I would say it was more like majority of the rollers felt extremely loose.

We haven’t noticed any performance issues; but now concerned with the reliability of the wheels if you are saying this isn’t normal.

If you haven’t noticed any performance issues, then you probably don’t have the same thing happening that Alex reported, however if you e-mail VEXpro support they can help you determine what is going on.

Paul

[Alex_Cormier]

I can tell you with certainty that is not normal. Something is wrong. Please contact VEX support and we can get you straightened out.

Will do, we also ordered 10 jaguars the other week, when we opened the box to use them this weekend. We noticed that 5 were not operational.