Bendalloy and Steel combination

[Silva]

If someone was a full Feruchemist and Allomancer and put up either a bendalloy or cadmium bubble and tried to fill a metalmind with speed, what would happen? Would it fill to your own personal time speed, the world around you, or not at all?

Hope no one’s asked this yet.

[RShara]

Okay, so you're saying if person A put up a bendalloy or cadmium bubble. Then while inside it, moved around and stored speed?

Using just bendalloy so I don't have to make the comparision twice

I'm pretty sure it would be that person's own relative speed, and not extra based on the time compression. It's the same as how you don't store more speed when falling than when walking. It has something to do with your own motive power.

[Weltall]

It would fill at the normal rate from the feruchemist's point of view, given how time passes for those inside any of Wayne and Marasi's bubbles. We have a WoB about Investiture leaking from a gemstone that invokes the same principle.

Quote

BlackYeti [PENDING REVIEW] (paraphrased)

If a gemstone infused with Stormlight were left inside a bendalloy or cadmium bubble, would the gemstone appear to go dun faster or slower respectively to the outside observer?

Brandon Sanderson [PENDING REVIEW] (paraphrased)

Yes it would. Time is actually changing, the same thing would be observed if it were brought near to a singularity.

source

If the rate of 'Investiture transfer' changed inside the bubble, the above wouldn't make sense.

Using Wayne as an extra illustration, when he's seen from an outside observer he's incredibly fast but when seen from his own persoective he's no faster than normal. There's no reason why he would store more or less speed based on being inside or outside a bubble. Or to use his specific powers, he wouldn't tap or store more or less health than normal in his own frame of reference. Let's imagine that a Bloodmaker ferring and Wayne both have an equal-sized goldmind and they both fill it for ten seconds, but Wayne does it while inside a speed bubble which he puts up as soon as he starts storing and drops as soon as ten seconds have passed in his frame of reference. Comparing both goldminds at the end you'd have the same amount of Investiture, Wayne would just fill his faster from the perspective of the ferring. Now, if Wayne kept up a bubble for ten seconds from the perspective of the ferring and stored for all that time, he would have more health stored in his goldmind than the ferring even though both appear to have store for the same length of time to an outside observer, but from Wayne's perspective he's been storing for something like eight times longer.

Edited July 11, 2018 by Weltall

[Journey Before Pancakes]

My understanding is that when you store speed, you're storing your self-relative movement speed; like how fast you can move your arms and legs from your own perspective.  So when storing it, you become sluggish, and when tapping it you become agile.

So I agree with RShara,  it wouldn't have any effect.  

Having it work the other way would lead to a lot of weird mechanics to deal with in feruchemy.   It's already bad enough you can compound as a twinborn; being able to do it with a non-compounding A-metal would be insane.