With the driveline fitted in the hull using lashings of epoxy glue (Hint: Hwen using the Poundland stuff, buy fresh tubes) the motor was going to have to sit at a funny angle due to the whopper prop fitted on the end of it.
I contemplated making a plastic support but decided to try something new. With several lumps of grey styrofoam kicking around, why not use this?
Chopping this to size worked well. I kept shaving bit away until the motor would fit with everything in-line. Half an hour's work and I had something that worked.
Thoe motor is fitted with UHU POR adhesive - a foam-safe clear glue. I wasn't sure about this, but it seems to have fixed the foam to the hull and motor strongly enough that when power is applied, nothing falls apart or even looks like it might. I wonder if the foam even provides some cushioning effects to keep things quiet?
Anyway, with things dry, I lashed up 6V worth of batteries and tried it in the pool.
You make a good point about using fresh adhesive - a point which is routinely hammered home to many people being trained to install strain gauges in their work.
ReplyDeleteIn fact, a number of strain gauge suppliers are so concerned about ensuring their gauges are properly bonded to specimens that, not only do they sell tested batches of adhesives (both cyanoacrylate and two part epoxy) from high end manufacturers, but they also put "use by" dates on the stuff - with the dates often being something like 6-12 months after the date of sale.
OK - some cynics might regard this as a marketing ploy - but there is sometimes a very noticeable difference in bond strength between what can be achieved using good, fresh, adhesive and what you get with other stuff.
It also goes without saying that strain gauges are a very critical (and fussy) application for adhesives.
By the way, I'm also reminded of something I was told when I did my industrial training with the CEGB - even 30+ years ago, the use of cyanoacrylate "superglues" outdoors was regarded as a definite no-no in the electricity supply industry. Over time, moisture would attack any bond - potentially leading to premature failure - if this happened with something safety critical like an insulator, the potential consequences wouldn't bear thinking about.