Wallenstein Thumb Gen 3 on BX24 still has issues

[mswlogo]

I have nothing against the Bro-Tek thumb I just personally like the Wallenstein thumb better. I like not having to attach and detach the link and I like the wide grip on the Wallenstein.

The overall design of the wallenstein is very nice.

A couple things happened I think that caused problems.

It was originally designed for the BX23.

That boom has more room and may have been slightly wider on teh BX23.

If folks were willing to weld a stop on the BX24, it worked fine.

The design of the Wallenstein wanted to take advantage of the the taper on the BX23 as a natural "stop". But you had a few tollerances that added up which caused it vary somewhat where it would stop. But on the BX23 you had a lot of room.

Another problem on the BX24 (don't know about BX23) is the boom is a C channel with an inset plate closing it off. The C channel is very thin. What would happen is the bolts would dig into that C channel and loosen the wedging effect of the taper. I don't know if the BX23 was thicker material or was a C channel versus a true box. But with the boom being slightly narrower (or variation in tolerances) you had little grip on the sides on the BX24.

The Bro-Tek strictly squeezes from the sides. If it relied on the taper to wedge they would have the same problem.

The "shims" mentioned was an attempt to lock in the thumb (again taking advantage of the taper) exactly where you wanted. This would put the pressure against that inset plate that closes the C channel (rather than the thin C channel ends that would wear down).

I gave them my suggestion for a very simple mod to allow it to squeeze from the sides like the Bro-Tek but still keep the same basic design.

I'm not sure if they are going with the shim or my suggested mod for Gen 4. They seemed to indicate they were going with my mod when I last spoke to them. They were waiting a long time on the feedback on the wedges.

They seem like a very nice company to deal with and will admit they needed to change it. They were very willing to listen my suggestion.

I think it was just a little bad luck in how the BX24 changed subtle enough to cause problems.

 

[Shmudda]

I have nothing against the Bro-Tek thumb I just personally like the Wallenstein thumb better. I like not having to attach and detach the link and I like the wide grip on the Wallenstein.

The overall design of the wallenstein is very nice.

A couple things happened I think that caused problems.

It was originally designed for the BX23.

That boom has more room and may have been slightly wider on teh BX23.

If folks were willing to weld a stop on the BX24, it worked fine.

The design of the Wallenstein wanted to take advantage of the the taper on the BX23 as a natural "stop". But you had a few tollerances that added up which caused it vary somewhat where it would stop. But on the BX23 you had a lot of room.

Another problem on the BX24 (don't know about BX23) is the boom is a C channel with an inset plate closing it off. The C channel is very thin. What would happen is the bolts would dig into that C channel and loosen the wedging effect of the taper. I don't know if the BX23 was thicker material or was a C channel versus a true box. But with the boom being slightly narrower (or variation in tolerances) you had little grip on the sides on the BX24.

The Bro-Tek strictly squeezes from the sides. If it relied on the taper to wedge they would have the same problem.

The "shims" mentioned was an attempt to lock in the thumb (again taking advantage of the taper) exactly where you wanted. This would put the pressure against that inset plate that closes the C channel (rather than the thin C channel ends that would wear down).

I gave them my suggestion for a very simple mod to allow it to squeeze from the sides like the Bro-Tek but still keep the same basic design.

I'm not sure if they are going with the shim or my suggested mod for Gen 4. They seemed to indicate they were going with my mod when I last spoke to them. They were waiting a long time on the feedback on the wedges.

They seem like a very nice company to deal with and will admit they needed to change it. They were very willing to listen my suggestion.

I think it was just a little bad luck in how the BX24 changed subtle enough to cause problems.

Logo,

Look at the thumb I designed and built. I believe this is what you are referring to. You will see that I compensated for the bolts digging into the "C" Channel of the Dipper Stick by designing a 1/4" thrust plate for the bolts to push against. This will also distribute the load across the Dipper Stick and will not be pushing and denting it at one location where the bolts are at.

The taper works, you just have to be smart enough to use it to your advantage.......

If properly designed as this one is you will have all the clearance in the world, and also the thumb wont move up the Dipper.

Craig

 

[mswlogo]

Logo,

Look at the thumb I designed and built. I believe this is what you are referring to. You will see that I compensated for the bolts digging into the "C" Channel of the Dipper Stick by designing a 1/4" thrust plate for the bolts to push against. This will also distribute the load across the Dipper Stick and will not be pushing and denting it at one location where the bolts are at.

The taper works, you just have to be smart enough to use it to your advantage.......

If properly designed as this one is you will have all the clearance in the world, and also the thumb wont move up the Dipper.

Craig

What function do your bolt(s) serve on that thrust plate side? I assume your thrust plate runs the full length and looks welded. It looks like a it will have a similar issue as the wallenstein where the bolt(s) are prevented from clamping sideways. But it looks like you have a pretty snug tolerance there which will help. Probably hard to cut tolerances that tight on a production unit.

This is the problem. If you clamp it really good sideways (two side plates not bridged with a welded thrust plate or welded collar in the case of the wallenstein), things will tend not to move (like a Bro-Tek, I don't think the bro-tek has the thrust plate and no issues have been posted). You weld a thrust plate in there to protect the force of the bolts on the "C" channel and then you reduce the sideways clamping effect (like yours and Wallenstien). I sort of modified the wallenstein into a "Hybrid" (still has welded thrust plate on one end and good clamping in the center and on the other end by floating the collar). It would be ideal if you could make your thrust plate float (tricky but doable) so the bolts can be 100% effective at clamping (on BOTH sides). You currently don't have two parallel plates clamped together like a Bro-Tek, you effectively created a C channel and clamped it on one side (piston side). Your bolts on the thumb side are more or less cosmetic, just like on the Wallenstein. Crank them all you want, you'd have to crush the thrust plate to make them grip the side walls of the dipper stick.

The Wallenstein has a welded thrust plate too where most of the force is. You can see it here near the drill bit.

It actually has a thrust plate on both sides (one floats). But the welded one (like yours) was part of what caused the problem in preventing it from clamping firmly. That combined with the collar preventing the other end from clamping. I debated about cutting the welded thrust plate too, but didn't want to weaken the purpose of that thrust plate (thrust plate is a good idea but it can cause issues too). Luckily the thrust plate didn't run the full length and there were no cosmetic bolts near it. On the wallenstein between the bolt near the center on the thumb side and the bolt near the collar it now has good clamping (after I floated the collar) and still has a functioning thrust plate where the major forces are. I think it's the best of both designs now.

 

[Shmudda]

The thrust plate between the two side plates is just floating in there, its not welded to anything, that was by design. It's actually held in by the (2) bolts on the bottom and the clamping force between the two side plates. When I made the thing I knew there was going to be a challenge with the side plates not gripping the dipper tight enough, so I made the thrust plate 1/16" narrower then the width of the dipper stick. The dipper is 2 7/8" wide, that thrust plate is 2 13/16" wide. I did that so the two side plates would actually bend around the dipper when the bolts are tightened and squeeze the thrust plate so it can't move, which it is indeed doing.

This is my first go around with a thumb, in fact the whole tractor, as I never owned a back-hoe before. With how it's tightened I really have no doubts that it won't work.

Craig

 

[mswlogo]

Oh cool. I'd like to see a picture how you floated that thrust plate. Hard to tell from the photos.

In this photo it looks like the thrust plate and the side plate is welded. Just curious. Is thrust plate welded to just one side plate?

 

[Shmudda]

Logo,

It is not welded at all to either side. The side plates were layed in reference to taper of the Dipper. The bolt holes were designed at a diameter of
.531" so that they would just clear the bolts as I wanted the plates at a certain spot on the dipper when it was pushed up tight. Please note all four bolts are wedged tight against the Dipper Stick, there is no way they can move up the stick anymore. The overall location of the side plates fell to within 1/32" of my intended layout (CADD system is great), so it went together as planned.

If you can open a PDF file of the drawing here it is, layout, details and all. I'm a firm believer of working the Engineering out first, then build! Some people dont do it in that order........

Can't wait to test the thing out.......

Craig

 

[mswlogo]

I think I see now. Hard to see in the photo. It must be paint or a refelction that made it look like it was one piece.

You really went to town on this thing, CAD and all

 

[Shmudda]

Has anybody had experience with the Gen 4 revision of what Wallenstein Thumb?? How's it working?

Craig

 

[MessickFarmEqu]

We've sent out about 20 of the Gen 4 versions and not heard any complaints.