Author Topic: that spring thing again  (Read 2629 times)

32 coupe

  • Hero Member
  • *****
  • Posts: 531
  • "Doc Johnson" on call !
    • View Profile
that spring thing again
« on: January 21, 2018, 08:06:24 PM »
OK, I have spent about 8 hours or so in the last 2 days on the beast with no success.


None of the linkages are binding, the rack is free with probibly 80% throw or better left at
730 rpm's.
The governor is free with no binding or excessive slop when I rotate the engine with
the spring off and moving the lever throughout its throw.

Warmed up , both cylinders will run within 5 degrees of each other.

I spent my time swapping springs trying to get the thing to pull 5kw.

Just won't do it.  At 730 rpm's and 1840 on the head  a 3kw load is no problem
The numbers are so close it's not worth mentioning.
BUT at 5kw load the engine is just starting to work a little the head will fall off to
52 hz from 62hz. Rpm's on the head will fall below 1600 at that point from 1840.
Don't remember the engine rpm's but you get the idea. Voltage will sag to 98 from the
120 it will normaly run.

I tried 12 or 15 different springs. Tried the original spring first. No luck.
Springs, combinations of springs, none stiffer than the original. No luck.
A few runs the springs were light enough the engine would just start to hunt a little.

I have noticed when I was setting throttle speed and no belt on the head the engine
would run with less vibration in the 800 to 850 rpm range. Maybe thats telling me
something.

The engine was rated at 25hp @ 1000 rpm's and I am running at 730 or so.

Not sure where to from here.

Gary




That little Kubota 4 cylinder engine is looking better all the time !


« Last Edit: January 21, 2018, 08:37:40 PM by 32 coupe »
Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

dieselgman

  • Hero Member
  • *****
  • Posts: 3189
    • View Profile
    • Lister Parts
Re: that spring thing again
« Reply #1 on: January 21, 2018, 08:59:41 PM »
The higher speed governors use lighter weights... maybe you just don't have enough governor weight installed for stable operation at 730rpm.

dieselgman
ALL Things Lister/Petter - Americas
Lyons Kansas warehousing and rebuild operations

mike90045

  • Mendocino Metro
  • Hero Member
  • *****
  • Posts: 1594
  • Mmmm BBQ
    • View Profile
    • Mikes Solar PV page
Re: that spring thing again
« Reply #2 on: January 21, 2018, 09:34:57 PM »
can you manually move the rack to maintain RPM's ?  my rack on single is real easy to move and change RPM and override the governor .

If you can't manually maintain RPM's, maybe its fuel delivery/timing or valve timing keeping things from fueling it enough  ?

32 coupe

  • Hero Member
  • *****
  • Posts: 531
  • "Doc Johnson" on call !
    • View Profile
Re: that spring thing again
« Reply #3 on: January 21, 2018, 10:23:40 PM »
yes, I can open the rack further.

I believe Gary is on the right track.

« Last Edit: January 22, 2018, 02:34:26 AM by 32 coupe »
Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

BruceM

  • Hero Member
  • *****
  • Posts: 3054
    • View Profile
Re: that spring thing again
« Reply #4 on: January 22, 2018, 03:41:26 AM »
+1 For Gary's comment.  You demonstrated to yourself no improvement even with a hunting-light spring, you have more power manually; it seems a governor weight issue. 

ajaffa1

  • Hero Member
  • *****
  • Posts: 1725
    • View Profile
Re: that spring thing again
« Reply #5 on: January 22, 2018, 06:47:13 AM »
Might be worth checking the numbers on the injector pumps, you are probably using Mico-Bosch pumps which I believe come with 7mm or 8mm elements. I am guessing a 25hp machine would require the larger pump element.

Bob

EdDee

  • Hero Member
  • *****
  • Posts: 773
    • View Profile
Re: that spring thing again
« Reply #6 on: January 22, 2018, 07:29:40 AM »
Hi Guys....

A cat amongst the pigeons for you all... Here is what I found bringing a 1000rpm engine to stability at 400/500/650/750 RPM....

The LENGTH and TENSION of the spring makes a very big difference to the response of the engine - too long soft and it will hunt badly.... Find a spring that almost does the job(Preferably 2 so you have a spare when you stuff the first one up), start the engine with the spring in system and shorten it, one or 2 coils at a time, till the response improves to your satisfaction... There should always be enough tension in the spring to fully open the rack when the engine is at rest, stopped. The spring should not be more than about 1 3/4 to 2 x its rest length when fully extended, ie at full governor closed position... If you find that you cannot get full rack opening, but the machine holds stable under low load, increase the length of the spring to one that has a greater number of coils.... Its a finicky dance, but one that can be done without the changing of governor weights...

Remember, the governor weights do not exert a linear increase in tension on the spring over the entire rev range too if they are allowed to travel too far... they exert a very low pull when the engine is running slowly, then go into a semi linear range as the arm weights are parallel/90 degrees with the cam shaft, then as they extend further, they can eventually go almost "over center" on some governors and go into a "non-linear" force mode for want of a better description... The trick is also to use the "near linear" areas of the governor travel to regulate the engine speed - If you find that hunting is a major problem, possibly shortening the linkage attached to the governor arm a bit will improve things as well... I have also found that when shortening this link, maximum power output, while affected, was not too bad - It was still "rolling coal" and had plenty of juice going to the pots to keep things stoked!!

Hope this helps...
Regds
Ed
12/1 750RPM/9HP Roid 5kVA- WMO Disposal/Electricity & Hot Water Gen
12/1 650RPM/8HP Roid 4.5kVa - Demon Dino
Chinese Yanmar - Silent Runner with AutoStart
Classic Komatsu 1963 Dozer/Fergusson 35 Gold Belly ...
Bikes,Cars,Gunsmithing & Paintball...Oh yes, a 5Ha open air Workshop to play in!

38ac

  • Hero Member
  • *****
  • Posts: 2324
    • View Profile
Re: that spring thing again
« Reply #7 on: January 22, 2018, 11:49:37 AM »
I would try a set of 650 rpm weights at this point I think. However it is possible that miss shaped arms on your weights are causing your issue. The 16/2 I just went through has the lighter weights and seems to have decent responce but in fairness  the only loading the engine has seen so far is a 4x4 agaist the flywheel rims, hardly scientific but I can kill it if I desire.
Collector and horder of about anything diesel