Treadmill

[BSAdadGriffindork]

What’s the consensus's on using a treadmill to break-in a car and also check axle alignment? Does more damage than good? Won’t damage at all?

Seems to be a lot of conflicting information out there.

Thank you!

[FatSebastian]

What’s the consensus's on using a treadmill to break-in a car and also check axle alignment? Does more damage than good?

I think you are on the right track (pun intended) by suspecting damage potential. What one person calls "break-in" others might describe as "wear-and-tear". Well-polished axles and bores shouldn't require an exhaustive break-in regiment, and without some kind of fixture it seems like a properly set-up rail-rider would eventually migrate to the edge of the treadmill and maybe fall off??? Even if there was no risk of damage (due to an accident or premature wear-out), it seems like an unnecessary contraption for gaining speed. One can use a dremel to "break-in" wheels as well, but we (and others?) found that it seemed to make things worse.

Now, someone on Reddit recently suggested that a treadmill helps with tuning the CoM location. I'd be curious to hear if anyone on DT has recent experience with treadmill testing!

[Vitamin K]

The guy who runs the StocKar Derby for our church's CSB group is a big proponent of the treadmill, both for testing drift behavior and for looking for wheel wobble. I can sort of see some limited utility in this, but the texture of a typical treadmill track sort of concerns me.

[BSAdadGriffindork]

What’s the consensus's on using a treadmill to break-in a car and also check axle alignment? Does more damage than good?

I think you are on the right track (pun intended) by suspecting damage potential. What one person calls "break-in" others might describe as "wear-and-tear". Well-polished axles and bores shouldn't require an exhaustive break-in regiment, and without some kind of fixture it seems like a properly set-up rail-rider would eventually migrate to the edge of the treadmill and maybe fall off??? Even if there was no risk of damage (due to an accident or premature wear-out), it seems like an unnecessary contraption for gaining speed. One can use a dremel to "break-in" wheels as well, but we (and others?) found that it seemed to make things worse.

Now, someone on Reddit recently suggested that a treadmill helps with tuning the CoM location. I'd be curious to hear if anyone on DT has recent experience with treadmill testing!

Here is the main source I found that supports it and gives fairly extensive instructions about it

https://www.[no advertising for this vendor].com/pinewood-derby-car-tuning/

But then I go to sites like this

https://www.turboderby.com/_files/ugd/1 ... 9bfba1.pdf

And it seems to be completely against to idea of it

[FatSebastian]

Here is the main source I found that supports it...

Ah, that helps. There are two advocated reasons for using the treadmill. One purpose is to "break-in" the lubricant or whatever; that is what the TurboDerby ebook mostly speaks against and the purpose that I have always associated with treadmill usage. Another purpose is to tune alignment, which TurboDerby also mentions but I was not really familiar with that aspect until you pointed it out (or else, I totally forgot that people do it ). Anyway...

In the treadmill video you cite, although the video title includes "Pinewood Derby 2019", it was actually posted Aug 20, 2011 and has a lot of views. The treadmill video starts by displaying a link to additional "written directions" for a "Break in Process" that's long gone (according to web.archive.org, the missing page hasn't been crawled since 2016). That's one clue that this technique is not just dated, but its accompanying content has since been censored by the proprietor. Troy explains in his intro section that the treadmill was employed as an alternative to "going in blind" (0:47) without any track testing, and that he was "tired of using tuning boards" (0:40) - I wasn't hearing any strong claim that treadmill tuning is vastly superior to other tuning techniques, just that it was certainly better than nothing.

Troy also says treadmill tuning can take 10-15 minutes or "might take up to an hour" (1:55). Note that a single derby heat will last about three seconds, with perhaps ten heats (so ~30 seconds of total track time per derby); thus, a treadmill tuning session is like running 20 - 120 entire derbies non-stop. On the treadmill, one can see the car wobble each time the tread-belt seam passes (4:25), so it appears that the belt irregularities can exaggerate behaviors, lending to the concern that Vitamin K expressed. And while there is a high-pitched drone that seems to be from the treadmill, at 5:00 Troy picks up the car and the squealing stops!

Re: concerns about damage, there's a follow-up video that's more telling: listen to the sound change when Troy picks up the car to adjust it at the 3:46 mark. That loud squeal is not from the machinery after all, but from the lubed wheels rolling!? Admittedly I have no experience with treadmill tuning, yet I wonder about the condition of the wheels after an hour of this...

Besides wear-and-tear, my main concern about aligning with the treadmill technique is that the car is effectively being drawn along uphill by a tow line, rather than falling (being pushed) under its own weight and being stabilized by the DFW against the rail - the (de)stabilizing dynamics are different. Almost certainly the string takes some of the pressure off the DFW and adds its own directionality, so the stabilizing performance of the DFW is augmented with the tow-line. Connecting the string at different points on the body may offer different stabilizing behaviors that beg for different tuning adjustments? My conjecture, FWIW, is that bent rear axles probably end up becoming better aligned using the treadmill, but costs extra wheel wear. And I am not sure how this technique optimally aligns the DFW.

Compare this to a more recent (and well-done) animation from the same business (presumably under later proprietorship) that shows how to perform alignment using... a tuning board!

[BSAdadGriffindork]

Here is the main source I found that supports it...

Ah, that helps. There are two advocated reasons for using the treadmill. One purpose is to "break-in" the lubricant or whatever; that is what the TurboDerby ebook mostly speaks against and the purpose that I have always associated with treadmill usage. Another purpose is to tune alignment, which TurboDerby also mentions but I was not really familiar with that aspect until you pointed it out (or else, I totally forgot that people do it ). Anyway...

In the treadmill video you cite, although the video title includes "Pinewood Derby 2019", it was actually posted Aug 20, 2011 and has a lot of views. The treadmill video starts by displaying a link to additional "written directions" for a "Break in Process" that's long gone (according to web.archive.org, the missing page hasn't been crawled since 2016). That's one clue that this technique is not just dated, but its accompanying content has since been censored by the proprietor. Troy explains in his intro section that the treadmill was employed as an alternative to "going in blind" (0:47) without any track testing, and that he was "tired of using tuning boards" (0:40) - I wasn't hearing any strong claim that treadmill tuning is vastly superior to other tuning techniques, just that it was certainly better than nothing.

Troy also says treadmill tuning can take 10-15 minutes or "might take up to an hour" (1:55). Note that a single derby heat will last about three seconds, with perhaps ten heats (so ~30 seconds of total track time per derby); thus, a treadmill tuning session is like running 20 - 120 entire derbies non-stop. On the treadmill, one can see the car wobble each time the tread-belt seam passes (4:25), so it appears that the belt irregularities can exaggerate behaviors, lending to the concern that Vitamin K expressed. And while there is a high-pitched drone that seems to be from the treadmill, at 5:00 Troy picks up the car and the squealing stops!

Re: concerns about damage, there's a follow-up video that's more telling: listen to the sound change when Troy picks up the car to adjust it at the 3:46 mark. That loud squeal is not from the machinery after all, but from the lubed wheels rolling!? Admittedly I have no experience with treadmill tuning, yet I wonder about the condition of the wheels after an hour of this...

Besides wear-and-tear, my main concern about aligning with the treadmill technique is that the car is effectively being drawn along uphill by a tow line, rather than falling (being pushed) under its own weight and being stabilized by the DFW against the rail - the (de)stabilizing dynamics are different. Almost certainly the string takes some of the pressure off the DFW and adds its own directionality, so the stabilizing performance of the DFW is augmented with the tow-line. Connecting the string at different points on the body may offer different stabilizing behaviors that beg for different tuning adjustments? My conjecture, FWIW, is that bent rear axles probably end up becoming better aligned using the treadmill, but costs extra wheel wear. And I am not sure how this technique optimally aligns the DFW.

Compare this to a more recent (and well-done) animation from the same business (presumably under later proprietorship) that shows how to perform alignment using... a tuning board!

Thank you for this very detailed analysis. Think I’ll stick with a tuning board haha

I appreciate all your helpful advice the past couple weeks!

[Loud2ns]

Think I’ll stick with a tuning board haha

The tuning board has served me well as I don't have a track set up yet. In fact, I've only seen my league cars run in person once at MA in '22! A suggestion.... get a piece of glass as the sound of the wheels tells you a lot about the car!!

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[BSAdadGriffindork]

Think I’ll stick with a tuning board haha

The tuning board has served me well as I don't have a track set up yet. In fact, I've only seen my league cars run in person once at MA in '22! A suggestion.... get a piece of glass as the sound of the wheels tells you a lot about the car!!

Sent from my SM-G991U using Tapatalk

Like make a tuning board out of 6’ of glass? Like a mirror or something?

[Loud2ns]

The tuning board has served me well as I don't have a track set up yet. In fact, I've only seen my league cars run in person once at MA in '22! A suggestion.... get a piece of glass as the sound of the wheels tells you a lot about the car!!

Sent from my SM-G991U using Tapatalk

Like make a tuning board out of 6’ of glass? Like a mirror or something?

I use about a 5' piece of glass on my dining room table. A mirror would work, though.

Just last week, we were tuning our Awana cars, and we had a wheel failure in the 11th hr. We grabbed last year's wheel and put it on the DFW. Ran it down the tuning board, and it made quite a racket. Even my wife in the other room asked what was going on because it sounded way worse than his brothers car! Swapped the DFW and the RR, and we sent it down. It sounded great because the outer edge on the original DFW was chowdered up, but the inner edge was great for the RR.

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