High speed idler motor for RPC ??

I'm shopping to buy a 5 or 7.5 hp rpc. Just don't have the time to study it and build one right now.

A local guy is making them. He's got a 7.5 hp Baldor 3400 rpm idler motor that he's made into a converter. Its self starting, but has no load balancing caps. $400.

Is there a disadvantage to the high speed motor? noise? I'm sure its been discussed here somewhere, but I didnt' see it in a 1/2 hr read. Anyway, I'm leaning toward just ordering one of the Anderson or other commercial converters off ebay. Any advise appriciated.


thanks
Jesse

I had a 3450 7 1/2. Still had the fan on it and was hard to live with the noise. I did like that it was essentially self starting - it would take off with a roll from my foot. It was just a motor shanghaied into RPC service

3450 rpm idlers work just fine. Their only drawback is the noise they make if they are fan cooled. If the idler is an open drip proof then the noise is much of a problem. The 3450 will start just fine if the RPC panel has sufficient start capacitors. I have used a 5 hp, 3450 for about 16 years and with no problems whatsoever.
1750 idlers also work quite well.

Bruce Norton
Kingsport, Tn

Noise.

Just noise.

Of course, you could buy the local machine (at that price, it'd be hard to beat against FleaBay and shipping, and you know what you're getting)...

And then, if you can't reasonably muffle it to suit your needs, hit the local scrapyard's motor-pile for a good-working low-speed motor that has a gnashed-up shaft.

I built my RPC with a 10hp 3750rpm motor, and after experimenting with noise-abatement, I stumbled (almost literally) on a brand-new 7.5hp Baldor 1750rpm unit that'd been shaft-damaged beyond economical repair. Scrapyard sold it out for the in-price (think it was about $18), so I toted it home, hacksaw'd the shaft off, made a nice cap to cover the end, and called it done...

...Oh... not quite...

I added one more contactor and a switch... and an outlet... If I happen to need 'a little more', I still have the 10hp motor tucked away, I run an extension cord from that outlet to the motor, flip the switch, and have 17.5hp of idler on-tap...

Bought a 5hp phase-o-matic

Just thinking about noise, and the uncertainty of someone elses' home built I passed on the 3450 convert. Bought instead a 5hp phase-o-matic thats only a few years old . It was local too. Included a couple 40amp three phase switches and 10' of SO. $350. Seeing how I didnt' have time to mess with makeing one at the moment I thought that was perfect.