Mountain Bike Reviews Forum banner
1 - 20 of 25 Posts

·
Registered
Joined
·
103 Posts
Discussion Starter · #1 ·
Because Thompson makes such bad ass precision machined parts, the tolerances for handlebar diameter are very low like 2 thousandths of an inch bigger and 0 thousandths smaller. This is nothing official or nothing confirmed simply speculation based off different measurements done at the shop.

What do you guys think?
 

·
Five is right out
Joined
·
3,176 Posts
"Possible Reason for Thompson Faceplate Cracking"

Because CNC just isn't the best way to go about making a faceplate in the first place. I couldn't actually understand the body of your post though.
 

·
Registered
Joined
·
201 Posts
womble said:
"Possible Reason for Thompson Faceplate Cracking"

Because CNC just isn't the best way to go about making a faceplate in the first place. I couldn't actually understand the body of your post though.
what is the best way to make a faceplate then. CNC is cut from a sold block of aluminum. the only thing to do to better would be to make it out of a stronger material. titanium would be a good on lite, strong and flexible.

As for the faceplate cracking tighten to the speck sheet that came with the stem.
 

·
Five is right out
Joined
·
3,176 Posts
motoxkfx123 said:
what is the best way to make a faceplate then. CNC is cut from a sold block of aluminum. the only thing to do to better would be to make it out of a stronger material. titanium would be a good on lite, strong and flexible.

As for the faceplate cracking tighten to the speck sheet that came with the stem.
Forging will make a stronger part as it modifies the grain structure of the metal during the process. CNC doesn't do this, and in some cases can cause stress risers. Or at least so says Sheldon Brown (I'm not a metalluragist) http://www.sheldonbrown.com/dp-forging.html

CNC is pretty and fancy looking. No denying that. But there have been enough pictures of cracked stems and faceplates to keep me away from it for critical parts.
 

·
Super Moderator
Joined
·
3,266 Posts
I imagine the failure rate is pretty low. IE people W/O cracked faceplates don't post up every month about it...

CNC'ing it doesnt make it weak.
Poor design can.
Improperly torquing can too..
How many here use a Tq wrench.
Hm?
CDT
 

·
Registered
Joined
·
10,039 Posts
John Kuhl said:
CNC (computer numerical control) is a
machine process, it has nothing to do with
the type of metal that is used. You can CNC
anything.

Best, John
I don't think that was in question. But we do know that forging creates stronger parts given the same design versus CNCed aluminum stock though. Like you said a forged piece could then be CNCed for final shape or looks; however we also know that Thomson does not forge them first. I think that makes it pretty safe to say the Thomson faceplates are not as strong as they could be.

Also, many of the people who post about this do claim to have used torque wrenches. Here's another thread about the faceplates
 

·
Super Moderator
Joined
·
3,266 Posts
boomn said:
I don't think that was in question. But we do know that forging creates stronger parts given the same design versus CNCed aluminum stock though. Like you said a forged piece could then be CNCed for final shape or looks; however we also know that Thomson does not forge them first. I think that makes it pretty safe to say the Thomson faceplates are not as strong as they could be.

Also, many of the people who post about this do claim to have used torque wrenches. Here's another thread about the faceplates
But that in no way means they are not strong enough.
Regardless of claims, I am always skeptical of post accident explanations...>If my kid cracks his head, he ALWAYS was not playing superman off the top stair. Always.
CDT <---- doubting Tom
 

·
Registered
Joined
·
10,039 Posts
CdaleTony said:
But that in no way means they are not strong enough.
Regardless of claims, I am always skeptical of post accident explanations...>If my kid cracks his head, he ALWAYS was not playing superman off the top stair. Always.
CDT <---- doubting Tom
judging by the number of posts about cracked Thomson faceplates versus faceplates from all the other brands out there, I will go out on a limb and say that no they aren't strong enough. It doesn't matter if a crash was involved or not because people are crashing with lots of other stems too. I do trust most people who claim they were JRA though; but then again I don't have any kids yet to teach me any better
 

·
Official ***** Idiot
Joined
·
333 Posts
womble said:
Forging will make a stronger part as it modifies the grain structure of the metal during the process. CNC doesn't do this, and in some cases can cause stress risers. Or at least so says Sheldon Brown (I'm not a metalluragist) http://www.sheldonbrown.com/dp-forging.html

CNC is pretty and fancy looking. No denying that. But there have been enough pictures of cracked stems and faceplates to keep me away from it for critical parts.
+1,000,000 for that. There's a reason you don't see CNC'd only parts on cars, except non-stress pieces like valve covers. They break easily. Even valve covers have a lower torque rating than forged, tighten too much, and you will crack the cover. Thomson probably has a problem with cracking because it's not a particularly thick part, it's bolted on far opposite ends of the part, and being yanked back and forth in the middle. It's going to give sooner than a forged part.
 

·
Super Moderator
Joined
·
3,266 Posts
heff® said:
+1,000,000 for that. There's a reason you don't see CNC'd only parts on cars, except non-stress pieces like valve covers. They break easily. Even valve covers have a lower torque rating than forged, tighten too much, and you will crack the cover. Thomson probably has a problem with cracking because it's not a particularly thick part, it's bolted on far opposite ends of the part, and being yanked back and forth in the middle. It's going to give sooner than a forged part.
Yawn. I've seen Billet CNC wheels on a car. I dont think its a forged block they start with. It certainly wasn't forged in the shape of the wheel as you expect, and CNC finished.
Steel valve covers are drawn, not forged. AL valve covers that crack easy are likely cast.
AL engines are cast, and CNC'ed...Low stress I guess.:rolleyes:

I bet Thomson knows alot more **** about making things than a bunch of us internet keyboard jockeys. If they had a serious issue with failure rates you would see a redesign.
I say once more, torqued wrong or wrong sequence stressing the FP.

But then again , in this thread, only ONE person knows the facts, and they are far away from any of our eyes, so who can say with authority??
CDT
 

·
Stay thirsty my friends
Joined
·
885 Posts
Wow, some real ignorance shown in this thread.

Heres some advice you can't screw up, buy forged 7075AL components, use a torque wrench.

How it was machined has nothing to do with poor design, incorrect material selection and user error in torque application. In almost all cases it's impossible to engineer out consumer stupidity, but in all cases its possible to engineer out design stupidity.

BTW Mtn biking is a dangerous hobby where you ride a two wheel human powered vehicle sometimes across unknown terrain at high speeds and periodically across risky inclines and have to negoitiate small and large solid hazards which may impede forward progress and possibly stop it completely no matter how fast or slow your going.Ride appropriately with caution and select components using common sense.

By signing below you accept all liability in reading this post realizing that life is hard, shiite happens and momma isn't always going to be there to kiss your boo boo's.

X_________________________________
 

·
Registered
Joined
·
10,039 Posts
CdaleTony said:
Yawn. I've seen Billet CNC wheels on a car. I dont think its a forged block they start with. It certainly wasn't forged in the shape of the wheel as you expect, and CNC finished.
Steel valve covers are drawn, not forged. AL valve covers that crack easy are likely cast.
AL engines are cast, and CNC'ed...Low stress I guess.:rolleyes:

I bet Thomson knows alot more **** about making things than a bunch of us internet keyboard jockeys. If they had a serious issue with failure rates you would see a redesign.
I say once more, torqued wrong or wrong sequence stressing the FP.

But then again , in this thread, only ONE person knows the facts, and they are far away from any of our eyes, so who can say with authority??
CDT
Yep, depending on the application and the design different methods of manufacturing will be most appropriate. CNC is obviously strong enough for their stem body and their seatposts without having to use any forging. The issue is that it isn't doesn't appear to be the best choice for this thin part with high stresses concentrated in small areas.

I'm sure they do have experts in design and manufacturing based on how much contract work they do for auto, aerospace and other industries, but they don't have any forging equipment and that would be a really big investment to add strength to a stem faceplate. Easier to just keep doing what you can

I don't think Thomson is too worried about the cracking issue because they don't seem to be directly losing any money because of it; they just charge $15 for a replacement faceplate instead of actually warrantying any of the failures I've heard about.
 

·
Super Moderator
Joined
·
3,266 Posts
boomn said:
Yep, depending on the application and the design different methods of manufacturing will be most appropriate. CNC is obviously strong enough for their stem body and their seatposts without having to use any forging. The issue is that it isn't doesn't appear to be the best choice for this thin part with high stresses concentrated in small areas.

I'm sure they do have experts in design and manufacturing based on how much contract work they do for auto, aerospace and other industries, but they don't have any forging equipment and that would be a really big investment to add strength to a stem faceplate. Easier to just keep doing what you can

I don't think Thomson is too worried about the cracking issue because they don't seem to be directly losing any money because of it; they just charge $15 for a replacement faceplate instead of actually warrantying any of the failures I've heard about.
You know with the intraweb and google we guys can go round n round with this.
You talk about forging as if you (A) know the reason for the failures, and (B) that forging equipment / laziness on LHT's part is the solution.

I think its probably a user problem myself.
If forging was the be-all end-all solution, and the equipment is SO pricey (Unlikely in this mfg economy) why couldn't they farm out the blanks to be forged by someone else?
Hm?
I think it's because they are smarter than us, and have it figured out.
Useless internet conjecture aside.
CDT
 
1 - 20 of 25 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top