ST15 vs ST20 rotor mass?

[dmarkh]

I posed the question to Tom at CGG but he didn't know the answer. I can see that they could be the same but I wonder if someone here might know the facts?

Thanks
Mark

[dieselgman]

We know the Marathon heads pretty well... and each 2 1/2kW increment of increased rating equals about 3/4 inch of extra winding length and mass on the rotor. (maybe about 15 to 20 lbs). Who knows what the Chinese are doing with the ST models???

dieselgman

[dmarkh]

We know the Marathon heads pretty well... and each 2 1/2kW increment of increased rating equals about 3/4 inch of extra winding length and mass on the rotor. (maybe about 15 to 20 lbs). Who knows what the Chinese are doing with the ST models???

dieselgman

Thanks for that dieselgman.

The ST manual I have says the ST20 weighs about 22 lbs more than the 15. Was your "15 to 20 lbs" per 2 1/2kw or total for the diff between the 15 and 20? Would all that 22 lbs the manual specifies be in the rotor?

I'm sort of fishing here because I am about to "over gen" my gen set from a ST10 to ST15 or ST20. Info I read on the Utterpower CD "recommends" that for an ST15 and my 1115 Changfa that I maybe should oversize the LoveJoy coupler to an L190 because of the rotor mass of the ST15. Something about the rubber spider maybe getting stressed during the "power stroke". I currently have an L150 coupler and have already purchased the L150 side for the 48mm shaft of the 15/20.

I can get an ST20 today from CGG or wait 2-4 weeks and get an ST15 from Diesel Electric out in AK. Basically for the same price too. I think I prefer the 20 at CGG (they are really good guys) but that rotor mass thing I read about has me a little worried. If it's "recommended" to oversize the coupler for an ST15, and the ST20 rotor mass is higher yet, than I'm inclined to wait and get the ST15 so I don't have to get a new L190 coupler. I'm also tight on space and already have to cut the shaft off at least an inch, probably a little more. The L190 is a little over a 1/2 inch longer than the L150.

I realize both are overkill for my 1115 but I'm doing this strictly for a "hard start" application. I'm not even changing out the 40AMP breaker I currently use for the ST10.

Again, I'm kind of fishing here. Should I go with the 20 from CGG or be safer and wait for the 15 from Diesel Electric? I'm sticking with the L150 coupler.

Sorry for the noise.

Thanks
mark

[dieselgman]

I do not have exact precise information even about the Marathons... but they tend to have extra heavy windings and core plates. I would not expect all the weight increase to reside in the rotor alone for any model as they usually increment both rotor and stator capacity together.

I operate Diesel Electric by the way (both Alaska and Kansas)... and our next container out of China will have the full range of ST product as well as other brushless generator types. We also do business with Tom at CGG and normally stock his product in our Kansas warehouse for inclusion with our engine kits. Our pricing is actually a bit under Tom's on an apples to apples comparison. Our ST heads are specified with all copper windings, all aluminum fans, all highest-quality name-brand bearings, all highest quality AVR controls. This costs quite a bit more initially but is worth it in the long run in problems avoided.

dieselgman

[dmarkh]

I do not have exact precise information even about the Marathons... but they tend to have extra heavy windings and core plates. I would not expect all the weight increase to reside in the rotor alone for any model as they usually increment both rotor and stator capacity together.

I operate Diesel Electric by the way (both Alaska and Kansas)... and our next container out of China will have the full range of ST product as well as other brushless generator types. We also do business with Tom at CGG and normally stock his product in our Kansas warehouse for inclusion with our engine kits. Our pricing is actually a bit under Tom's on an apples to apples comparison. Our ST heads are specified with all copper windings, all aluminum fans, all highest-quality name-brand bearings, all highest quality AVR controls. This costs quite a bit more initially but is worth it in the long run in problems avoided.

dieselgman

Well I'll be damned. I guess if I had been around here longer I would have known this. I feel sort of stupid ya know. I am about to pull the trigger on one of them. Do you think given my circumstances I would be better off with the ST15? I'm sure it would handle my "hard start" problem. I can wait for it.

Mark

[vdubnut62]

I told ya that Gary was a member here. dieselgman And from my experience he is a real stand up fellow. So is Tom Osborne of CGG.
Ron.

[dmarkh]

I told ya that Gary was a member here. dieselgman And from my experience he is a real stand up fellow. So is Tom Osborne of CGG.
Ron.

Ya, I see that now. Certainly my small praise for CGG did not imply I thought anything wrong with Diesel Electric? I tend to overlook the names people use on these lists and just assume responses are just a personal "help of a newbie" type that I really do appreciate. Even in my emails to gsj@gci.net where they were signed as Gary" I didn't make that connection in my head. Getting to be that age where only certain things are retained.

Either way, I did just make a deposit on an ST15 from Diesel Electric so to be sure to get one. And I'm sure I will be very happy with it. The ST20 just worried me a little.

Mark

[dieselgman]

We love doing business with Tom at CGG. He is just a fine personable gentleman and seems to run a fairly tidy business. Our time and energy for importing has always focused on the Lister parts in the past and China has been a bit difficult to get started with. I think some of the language and cultural barriers are an issue at times in dealing with Chinese manufacturers. Even basic technical language seems to fail in translation to Chinese. We shall see shortly if they can follow instructions and deliver on all promises. I know they are technically capable engineers in their own right and that most of the big brands are now manufactured there - Marathon is among the crowd to have shifted their manufacturing operations out of the USA to the Chinese mainland.

dieselgman

[vdubnut62]

I have "Senior Moments" all the time. I think it's caused from too much life experience crammed into too small a space . Either that or I killed too many brain cells in my miss-spent
youth.  
 I think I claimed to have an st15 in an earlier post......well, I don't. I have 2 st12 heads. Yep, that was another Senior moment.  I would like to know the diff in the ST20  rotor weight too.
Ron.