PRT build on hold *Build completed*

[sidespill]

So there I was had the workstation all ready. Built my Downboy 917, tested and it worked /ubbthreads/images/graemlins/thumbsup.gif . Then I solder a neg lead to the ECan. Fix the TWOK to the head. Home stretch I go to pot the board in the ECan first part of AA good second part of AA NOOOOOOOOO!!!!! I'm all out. Why all the drama you say. Well this is my first PR-T build. I was almost there and then i came to a workstop cause i ran out of AA. It was worse than taking a shower then realizing the shampoo's all tapped. What do you guys suggest? Pot the ECan with regular epoxy or order some AA and wait? Has anyone potted ECan with regular epoxy?

 

[darkzero]

Re: PRT build on hold

I always pot my electronics with Devcon 2ton epoxy mixed with alumina oxide powder. For your PR-T build, regular epoxy should be fine. Using AA to pot them is way too expensive IMO. I only use AA to pot the emitter and the eCan to the head.

 

[Darell]

Re: PRT build on hold

I've used regular epoxy in a pinch as well - has worked fine. Be nice to find some cheap, heat-resistant goop for this use. It is somewhat of a waste to use AA (or worse - AS like I used to use!). But you need something in there strong enough to hold the circuit against the constant push of the springs.

 

[sidespill]

Re: PRT build on hold

Yeah it looks like I'll press on with the build thanks guys. I'm considering scuffing the inside of the ecan to help the epoxy bond to it better. I've read of others having problems with different battery packs pushing up on the board and actually having it shift forward far enough so the anode contact looses connection.

 

[Darell]

Re: PRT build on hold

Roughing the inside walls of the can would help, for sure. You can go the next step and even drill some little divots in there for more grip as well. Boy, I've never had one more on me though, and I never go overboard on my potting. I first glue the board down to the lip, and then I back it up with just enough goop to contact all the edges.

And the final step - I just use the smallest little dabs (2-3) or epoxy on the wide lip face to hold it up into the head. Doesn't take much to hold it, and with only a little epoxy there is a chance that you can remove it later if desired (like if your board shifts inside!)

Good luck. These are fun, and the results are worth it!

 

[McGizmo]

Re: PRT build on hold

I also think regular epoxy would work. I normally use a bunch of AA epoxy after using CA to bond the PCB to can. I get about 4 or 5 "builds" from a set of AA tubes. I may have a couple bucks in epoxy in each build but I have never had the PCB or E can come loose on me. I also figure that the AA is better than static air in thermal relief. /ubbthreads/images/graemlins/icon3.gif I have noticed that the S. Diode (I think that's the component) gets real hot real fast, on the DownBoy, so I figure a nice mass of AA might be providing some relief for it. Instead of a conformal coating, I am going for conformal burial. /ubbthreads/images/graemlins/blush.gif

 

[sidespill]

Re: PRT build on hold

Finished it up this morning. I went ahead and used the Devcon 2 ton to pot the PCB. I used CA glue to first attatch the PCB to ecan. I thought about going light on attatching the can to the head but decided against it. I wanted everything solid at the expense however of making the thing permanent. Like I said I finished everthing up this morning so I only got to fool around with the light in my basement. I wanted to build the PR-t mainly due to curiosity. There has been a lot of hype about these heads coupled with the DB 917 that I had to see for myself. What do I think? It's definately an improvement over the stock E2e. I think it's a keeper. I bought 1 of the last 5 PR-T's from the shop and I'm glad I took my sweet *** time building it and making as perfect as I could. Well finally I just wanted to say thanks dark,darell,and Mcgiz. I posted for particular advice and got responses from modders with credential and the designer. More than I expected.

 

[Rothrandir]

Re: PRT build on hold

i'm one to overkill whenever possible, and when you pot the ecan and led completely, it tends to use up almost an entire set of aa /ubbthreads/images/graemlins/eek.gif /ubbthreads/images/graemlins/icon15.gif

the extra expense is well worth knowing that it is extra durable.

 

[Darell]

Re: PRT build on hold

Great to hear that you got it together, sidespill!

[ QUOTE ]
McGizmo said:
I also figure that the AA is better than static air in thermal relief. /ubbthreads/images/graemlins/icon3.gif

[/ QUOTE ]
Yeah, I've always wondered about this. Our goal for the really hot stuff is to transport the heat to the outside into the "free air." But this, of course is static air in the can. My patented non-scientific *thinking* of the issue doesn't make one solution jump out as the obvious correct one. When covered with a ton of AA, the hot components may be more insulated, and therefor subject to *higher* temps than if the heat could bleed off into the surrounding air.

This is for sure going to be a tough one to accurately determine. I think I'll punt. And go buy more AA.

 

[MR Bulk]

Re: PRT build on hold

[ QUOTE ]
Rothrandir said:
i'm one to overkill whenever possible, and when you pot the ecan and led completely, it tends to use up almost an entire set of aa /ubbthreads/images/graemlins/eek.gif /ubbthreads/images/graemlins/icon15.gif

the extra expense is well worth knowing that it is extra durable.

[/ QUOTE ]

Cheapest way is to use "Thermal RTV" silicone. Works pretty good too.

 

[Rothrandir]

Re: PRT build on hold

i've heard thermal rtv mentioned before, but on a journey to find some (this was probably about 2 years ago, after first joining cpf), i wasn't able to find any.

is it a hard epoxy thing? or more like a silicone rubber?

 

[McGizmo]

Re: PRT build on hold

Well as I understand it, trapped air is more of an insulator than just about any solid material. /ubbthreads/images/graemlins/icon3.gif I agree with Charlie on the use of thermal RTV to fill the void in the various modules as preferred to nothing at all. It proved itself to be sufficient in the Pelican McCapsules to prevent the thermal shutdown of the Bad Boys, as I recall.

However in the E-can, I prefer the more rigid AA not because of its greater thermal transfer over the RTV but because it provides more structural integrity in compression of the battery train. The one aspect of the E-can that I wish were diferent is the location of the mounting ledge in the E-can for the PCB. I would much rather the PCB were dropped down from the back end and that the board were pushed against the can's lip in compression and not away from it. Unfortunately, the components can't all be located further into the interior of the PCB allowing for a clear perimeter where it could sit on a ledge. The CA bond between the PCB and the lip of the E-can may be sufficient for bearing the compression load but I feel much more comfortable with the AA filling most of the can and being spread on the walls of the can completely. /ubbthreads/images/graemlins/icon3.gif

I also post cure every build as I believe it raises the HDT of the epoxy and enhances its structural abilities at elevated opperating temperatures. From what I have read and gathered in others posts along the way, I am likely guilty of overkill here but like Roth, (I believe) I don't want a failure due to something I could have avoided. Murphy has his way of keeping me honest, and then some!

On the very few PR's that I had to take apart due to converter failure, I have heated them to 180F and then used a metal punch that is small enough to go into one of the LED lead holes along with a hammer. I figure the E-can and converter are a write off at this point. If need be, you can drill a larger hole through the bulkhead for the punch access. Judging by the amount of hammering required on the "hot" part, the structure, under normal abuse, is sound. /ubbthreads/images/graemlins/icon15.gif

 

[StoneDog]

Re: PRT build on hold

I used plain old JB Weld to pot my DB1000 a few weeks ago. I've used it quite a bit and haven't had a problem.

In fact, I used it as the filler for a few sammiches too - worked perfectly!

Jon

 

[kakster]

Re: PRT build on hold

Isnt JB Weld conductive?

 

[StoneDog]

Re: PRT build on hold

I've read here that it is mildly conductive, but I called the manufacturer just to be sure. According to them it is an insulator and the woman that I talked to rattled it off so fast I think it wasn't the first time she'd answered that question. /ubbthreads/images/graemlins/smile.gif

Like I said, I've used it on DownBoy and MadMax boards without any problem.

Jon