Anyone ever snap a "Optional" Tekno universal shaft?

[Supradude26]

So I had my first casualty with either of my Tekno rigs yesterday at the track with the et48.3. Came down slightly angled and hit with the right rear wheel first from an average size jump and the axle shaft snapped right where the pin goes through for the hub. When I built it last month I bit on the option of the universal shafts, but this seemed to be a weak spot or something. I'm pretty sure they aren't rebuild able and I'm guessing I'll have to shell out another $50.00 for two, but at least I have the stock cvd's I never put in for now... Anyone seen this happen before?

 

[TBuggy]

I don't have an ET but I do have an EB with universals and I don't recall the end of having two sets of holes for the hubs? Was your rig brand new when you got it? Did you modify it at some point? I am just guessing that it was a modification that weekend that point.

I did a little part search and all the pics I pull up of the ET48.3 universals don't appear to have two sets of holes.
Screen shot of some brand new parts listed online;

 

[Chainsaw10]

Tbuggy is correct...there should not be 2 sets of holes for the axle crosspin. That second hole leaves that axle really weak at that point. Strange that there’s 2 holes

 

[Billl DeLong]

50% warranty on all parts mailed into TEKNO, no questions asked:
https://www.teknorc.com/warranty-repair/

 

[Supradude26]

I don't have an ET but I do have an EB with universals and I don't recall the end of having two sets of holes for the hubs? Was your rig brand new when you got it? Did you modify it at some point? I am just guessing that it was a modification that weekend that point.

I did a little part search and all the pics I pull up of the ET48.3 universals don't appear to have two sets of holes.
Screen shot of some brand new parts listed online;
View attachment 1549

There aren't 2 holes, it just looks like it because of the lightened hub had extra holes so it changed the color of the axle metal where it was touching is my guess. Just one hole, and everything was brand new from amain last month.. mine are just like those new ones in the picture.

 

[Supradude26]

Here is a close up of one of the others, showing the hole and the other marks..

 

[TBuggy]

There aren't 2 holes, it just looks like it because of the lightened hub had extra holes so it changed the color of the axle metal where it was touching is my guess. Just one hole, and everything was brand new from amain last month.. mine are just like those new ones in the picture.

Ah, I see now! That picture totally had me fooled! LOL!

Well in that case what @Billl DeLong has said, is the best advice for replacement. Tekno is super cool when it comes to their warrantee. I have asked them all sorts of questions on what ifs and is this part or that part count, answer is always the same. If it is something they have in stock you will get the 50% off the replacement part. That being said you will only need to send that one broken axle in and you will get the discount on a new set...extra bonus if you ask me!

 

[Supradude26]

Ah, I see now! That picture totally had me fooled! LOL!

Well in that case what @Billl DeLong has said, is the best advice for replacement. Tekno is super cool when it comes to their warrantee. I have asked them all sorts of questions on what ifs and is this part or that part count, answer is always the same. If it is something they have in stock you will get the 50% off the replacement part. That being said you will only need to send that one broken axle in and you will get the discount on a new set...extra bonus if you ask me!

That's cool. I sent them a email last night when I got home and tore the car down as they want pictures and stuff. In RC we break stuff. It's the number one frustrating thing about this hobby, especially when we go with big power and high speeds, but I was just sort of surprised that this broke on a landing that my old Tamiya Frog I got in 1989 would have handled. Plus their was no signed at all that it may have cracked or bent somehow earlier, but decided to break when I landed on that wheel first.

All in all I cant complain because I've run close to 20 packs through this truggy and another 5 or 6 now through the SCT and this was the first part to break on either vehicle. And that's over 29 minutes of runtime per charge. Only other thing that sidelined me was when I hit a small tree going about 10mph and I bent the inner hinge pin and broke a steering ball link. That was my fault though.

I dont know if your is the same as mine, but the one thing I dont like about the universals is I had to swap the inner hub bearings out for smaller ones that sit really close to the outer ones. Just seems like there isnt nearly as much support because they are so close together and that it would put way more strain on the bearings. I actually had to throw away all 4 inners yesterday when I switched over. I also had to order and install 2 or 3 shims on each wheel to get rid of some slop which when I run the big 6 3/4" monster truck tires and wheels with 1/2" offset got amplified quite a bit. I may end up leaving the CVD's in for now to see if I can notice any difference on the track.

 

[Billl DeLong]

I have never taken a picture, I simply fill out the PDF form (linked above) then mail my broken parts in and it typically takes about a week or two for them to give me a discount coupon code which I use to get the 50% discount on the broken parts I mailed in... I also send in my old worn out lexan bodies too!

 

[RC_User]

That's cool. I sent them a email last night when I got home and tore the car down as they want pictures and stuff. In RC we break stuff. It's the number one frustrating thing about this hobby, especially when we go with big power and high speeds, but I was just sort of surprised that this broke on a landing that my old Tamiya Frog I got in 1989 would have handled. Plus their was no signed at all that it may have cracked or bent somehow earlier, but decided to break when I landed on that wheel first.

All in all I cant complain because I've run close to 20 packs through this truggy and another 5 or 6 now through the SCT and this was the first part to break on either vehicle. And that's over 29 minutes of runtime per charge. Only other thing that sidelined me was when I hit a small tree going about 10mph and I bent the inner hinge pin and broke a steering ball link. That was my fault though.

I dont know if your is the same as mine, but the one thing I dont like about the universals is I had to swap the inner hub bearings out for smaller ones that sit really close to the outer ones. Just seems like there isnt nearly as much support because they are so close together and that it would put way more strain on the bearings. I actually had to throw away all 4 inners yesterday when I switched over. I also had to order and install 2 or 3 shims on each wheel to get rid of some slop which when I run the big 6 3/4" monster truck tires and wheels with 1/2" offset got amplified quite a bit. I may end up leaving the CVD's in for now to see if I can notice any difference on the track.

My heart sank when I read this, about how the unis dont fit in the hub the same way. I have a set new that I haven't installed and I just looked at them to see what you mean. I agree that is an odd design how the inner bearing isnt at the same place as the CVDs and sits inside of the hub and doesnt support it as well.. yuck. I wonder why tekno designed them to fit like that.

 

[Supradude26]

My heart sank when I read this, about how the unis dont fit in the hub the same way. I have a set new that I haven't installed and I just looked at them to see what you mean. I agree that is an odd design how the inner bearing isnt at the same place as the CVDs and sits inside of the hub and doesnt support it as well.. yuck. I wonder why tekno designed them to fit like that.

I found some 8mm shims at AMain (CRC or something like that) and found that putting 2 on each wheel got rid of pretty much all the loose wiggle that the wheels had with them. Tried 3 but the hexes were binding against the hubs. I also used pretty cheap bearings on the inner position so maybe they werent quite as precise in size. I have a set of the Tekno bearings in my shopping
cart now... I'll stick with theirs once I get the uni replaced.

 

[Overkill]

My heart sank when I read this, about how the unis dont fit in the hub the same way. I have a set new that I haven't installed and I just looked at them to see what you mean. I agree that is an odd design how the inner bearing isnt at the same place as the CVDs and sits inside of the hub and doesnt support it as well.. yuck. I wonder why tekno designed them to fit like that.

I run the Arrma CVD’s in both my truggies and they install the same way as the Tekno universals, and I’ve never had any type of issue with the bearing support.

 

[Supradude26]

I run the Arrma CVD’s in both my truggies and they install the same way as the Tekno universals, and I’ve never had any type of issue with the bearing support.

I'm sure they did their research when they designed it that way, I was just a little surprised when I was building the kit that there was only about 3.5mm of space between the inner and outer bearing when the CVD appears to have at least 4 times that amount. It seemed to be the main reason I had to get some shims to get rid of wheel slop. I dont think it's why my universal broke however.

 

[Matthew_Armeni]

The pivot point of the uni and the CVA's are located at a certain point within the spindle for the best performance. The CVA can be captured by a large bearing but the uni cannot, hence the inner bearings for each have to be at different location within the spindle.

 

[RC_User]

Im totally nitpicking here.
I'm wondering why the uni stub axles couldnt be a bit longer, then a big bearing could possibly be used in the same place on the spindle as the CVAs. I wonder if the unis have to sit inside the spindle further for the joints to have enough room without hitting the hub carriers, whereas the cvds joints are already inside the spindle. Not sure. Im guessing the vehicles were not designed for the unis originally or they would have come with them with a similar installation as the CVAs where the bearings support them better.
I dont doubt that the beefier arrmas have no durability issues. I just dont like how the unis have to install with the smaller bearing inside the spindle, supporting the stub axle less than the CVAs... but I guess we are lucky to have the option. I thought earlier that most 1/8s come with unis but I looked at a few and see now that they dont, looks like CVas are the standard, mugen has a uni option too but I couldnt see in the manual how they install for curiosity.

 

[Matthew_Armeni]

As I mentioned in the post above, the uni and the cv need to have the pivot point in a certain location within the spindle and the hub. In the rear it's less important but it still affects the handling of the car. In the front it's a big deal, the axle needs to pivot at the same axis as the spindle otherwise the driveshaft will swing back and forth as the car steers.

With regards to the bearings, 8x16's are some of the most durable rc bearings there are. The outer bearing on almost all 8th scales use 8x16's. If the company is using unis they're almost assuredly using 8x16 inners as well. Some companies use 8x16 inners when using cv's and just capture the pin with a sleeve.
If we put more space between the 2 8x16's (almost all companies are using ~2mm) we'd need a longer hub, which would work but then we'd be increasing the scrub radius of the tires, not ideal.

I promise you that we do as much as we can to make our cars as durable as possible while maintaining the best geometry possible. Point in fact, the uni design on our .4 buggies is a little less durable than the .3 buggies and truggies, which is one of the reasons you don't see us running .4 stuff on our truggies, we'd be forced to always run cv's because that uni design wouldn't last long enough in a truggy for us to feel comfortable selling it.

 

[Supradude26]

As I mentioned in the post above, the uni and the cv need to have the pivot point in a certain location within the spindle and the hub. In the rear it's less important but it still affects the handling of the car. In the front it's a big deal, the axle needs to pivot at the same axis as the spindle otherwise the driveshaft will swing back and forth as the car steers.

With regards to the bearings, 8x16's are some of the most durable rc bearings there are. The outer bearing on almost all 8th scales use 8x16's. If the company is using unis they're almost assuredly using 8x16 inners as well. Some companies use 8x16 inners when using cv's and just capture the pin with a sleeve.
If we put more space between the 2 8x16's (almost all companies are using ~2mm) we'd need a longer hub, which would work but then we'd be increasing the scrub radius of the tires, not ideal.

I promise you that we do as much as we can to make our cars as durable as possible while maintaining the best geometry possible. Point in fact, the uni design on our .4 buggies is a little less durable than the .3 buggies and truggies, which is one of the reasons you don't see us running .4 stuff on our truggies, we'd be forced to always run cv's because that uni design wouldn't last long enough in a truggy for us to feel comfortable selling it.

Everything you say makes perfect sense, I guess I was just surprised when it broke, and that the bearings sit so close together. Dont get me wrong, I bought the ET48.3 5 weeks ago, and loved it so much that less than 2 weeks later I ordered and built the SCT410.3. Next will be the EB48.4. I love these Tekno vehicles. I've been building and running RC for over 25 years but have never raced, and ever since i got these two i find myself at the local track practicing every time the weather permits. Looking like its gonna be raining for the better part of 5 months now though, and the only indoor track anyplace in my area is over an hour away..