Back Purge Setup - Bicycle Framebuilding

[ToddFarr]

Hey all,
Looking to setup a back purge system. Tried search the forum and there is not too much on the topic.

My first project will be to setup a back purge on my bringheli, can anyone give me the low down on whats desired?

1.) I know you need to VENT somewhere. Looking at the Sputnik and Anvil it looks like they dump from the Top of the Seat Tube, this is probably because Argon is heavier than Air and it will push it down and out but where? Do you want to push down and out to a vent in the BB or out the Chain Stays?

2.) I know I need a Dual Regulator/Flow Meter. Any recommendations?

Thanks in Advance - Todd

[Alistair]

Hey all,
Looking to setup a back purge system. Tried search the forum and there is not too much on the topic.

My first project will be to setup a back purge on my bringheli, can anyone give me the low down on whats desired?

1.) I know you need to VENT somewhere. Looking at the Sputnik and Anvil it looks like they dump from the Top of the Seat Tube, this is probably because Argon is heavier than Air and it will push it down and out but where? Do you want to push down and out to a vent in the BB or out the Chain Stays?

2.) I know I need a Dual Regulator/Flow Meter. Any recommendations?

Thanks in Advance - Todd

Todd,

check out this thread from the Google group,
https://groups.google.com/forum/?fro...s/zEkd_4eBxlEJ

and this one from the MTBR group,
Two tanks or dual out put flow meter for back purging?

The discussions there, and any answers you get from the thread here, should give you a good idea of what your options are.

Alistair.

[VertigoCycles]

Hey all,
Looking to setup a back purge system. Tried search the forum and there is not too much on the topic.

My first project will be to setup a back purge on my bringheli, can anyone give me the low down on whats desired?

1.) I know you need to VENT somewhere. Looking at the Sputnik and Anvil it looks like they dump from the Top of the Seat Tube, this is probably because Argon is heavier than Air and it will push it down and out but where? Do you want to push down and out to a vent in the BB or out the Chain Stays?

2.) I know I need a Dual Regulator/Flow Meter. Any recommendations?

Thanks in Advance - Todd

Be smart about where you put your purge lines. My Anvil fixture has them at the BB, ST and HT...they might not all be necessary there, but I'm sure it speeds up the fill process. Vent holes at each joint so the frame can fill and vent holes at or near the dropouts so air can be pushed out.

FYI - my way is obviously not the only way, but I have a tank dedicated to purging. I start with 12-15 CFH and the frame oriented with the HT facing down (so my stay vents are at the highest point) and after about 10min I back off to about 7 CFH and get to welding.

Any holes not intended to be ventilation need to be plugged. For example, I drill my ST slot relief before building the frame and I have a stainless plug for it. The vent hole for the DT/BB is similarly plugged when I weld the front edge of the ST miter to the BB shell before setting up the entire main frame for tacking.

[ToddFarr]

Thanks for the reply guys! It's really helpful. I started my Back Purge setup for my Jig, now I'm looking to move to the Heat Sinks and Purging on the stand.

I'm debating whether or not to machine my own heatsinks. One in particular is the BB Heatsink, Looking at the one on the Paragon site it would be hard to make that for much less than that already is. 510 Bronze is pretty expensive and not the easiest to machine. Is this a typical material for heat sinks? Also sounds like the paragon will only fit paragon shells?

Here is a picture of the HT and ST cone I made for the Bringheli this weekend. I think I'm going to make a whole new BB Tower. There is not much I can do with the current one.

[Alistair]

I'm debating whether or not to machine my own heatsinks. One in particular is the BB Heatsink, Looking at the one on the Paragon site it would be hard to make that for much less than that already is. 510 Bronze is pretty expensive and not the easiest to machine. Is this a typical material for heat sinks? Also sounds like the paragon will only fit paragon shells?

Todd,

I made my own, mostly because I thought it would be a good exercise in design and fabrication, and a bit of a challenge. It was a somewhat time consuming project, partly because I'm still relatively new to machining and partly because I had to figure it all out from scratch, design and materials wise. I've never gotten a look at anything like this in person before, that would have made it easier to steal some ideas. Anyway, having gotten it all figured out now and made a few, any more that I make will go a lot quicker.

I went with the cored bronze (SAE 660) that Enco always seems to have on sale in their monthly flyer thingy. Pretty affordable. Machines nicely, gives a good finish. I ground up some HSS bits with zero back rake which seemed to help a lot, preventing the tool from digging in and being "grabby".

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Here's a link to a Flickr set that gives an idea of the steps involved, complete with some old fashioned 2D AutoCad sectioned drawings ('cause I can't afford SolidWorks...).

That all being said, I don't see how you could go wrong with the offerings from Paragon and Sputnik. Considering the work involved, their prices are very fair I think.

Hope this helps.

Alistair.

[Alistair]

Here's a link to a Flickr set that gives an idea of the steps involved, complete with some old fashioned 2D AutoCad sectioned drawings ('cause I can't afford SolidWorks...).

Oops, forgot the link. Here it is, Purgeable heat sinks. - a set on Flickr

Apologies.

Alistair.

[VertigoCycles]

the nice feature of the Paragon BB tool is that it expands first and then you tighten up the caps...a nice feature when you're capping both sides. all the tools I made are like Alistairs (though not as nicely made) where they expand and load the cap in one operation.

unless you have a lathe and mill with some serious power, super sharp tools and a very rigid setup, avoid the 510. the cored 660 gets the job done and it's cheaper as well as much easier to machine.

[fortyfour]

I have recently been doing research to finalize my own back purge system. While doing key word searches (both via Google and Flickr) I was finding that 44 BIKES was coming up mostly for back purge searches... Me. The one looking for information? So for the sake of this thread, and to return the favor (Sean at Vertigo was kind enough to answer a few questions of my own), I organized all of my back purge set up images into one dedicated Flickr Set. By no means complete nor expert opinion but now it's all in one place, organized and tagged appropriately. More to come as I convert my heat syncs appropriately and make some modifications as well. Thanks to all who have helped with answering questions. Enjoy:

44 Bikes : Back Purge Setup

[Too Tall]

Kristofer Henry, with that last post this thread is going into "The Knowledge" and tag you are it.

[Alistair]

I organized all of my back purge set up images into one dedicated Flickr Set. By no means complete nor expert opinion but now it's all in one place, organized and tagged appropriately. More to come as I convert my heat syncs appropriately and make some modifications as well.

Nicely done Kris. Your Flickr pic's, and some advice I got from Sean via email, were what gave me the inspiration to make my own heat sinks.

I don't think I mentioned that in my above posts, so I'm mentioning it here because I think it's important to acknowledge when builders are kind enough to share information (whether it be in the form of words or pictures) that is helpful to another builder who is trying to solve some issue or other.

Cheers.

Alistair.