G5200 with front mount debris blower...losing rpm....too much for engine?

73blazer · Dec 9, 2019

SO I picked up a New Holland 708D debris blower for a very fair price. It is exactly the same as the F2535D debris blower for F-Series mowers. It has the quick attach mount and was already converted to electric nozzle rotation, and I have the quick mount front hitch for my G5200 which I run a G2003 blade and G2546 snow blower on it, no problems running these implements.
I figured this debris blower might be a bit much for this G5200 and my fear was confirmed when I hooked it up. It runs it, but what happens it is won't reach full RPM and blows alot of black smoke. Basically I engage PTO very slowly, then crank up the RPM's, about 2/3's of the way up, no RPM's are to be had as you keep moving the throttle up and it just starts blowing smoke. It's spinning it decently, but when I disengage the PTO it jumps up to full RPM. So under load it's lost RPM and blowing smoke. How many RPM does it lose, I dunno, but my guess is at least a couple hundred.
I knew it was a crapshoot when buying it, but if there's something I can do to make it work, i'd give it a go.
The guy I bought it from had it on a G1800 (16hp) and it didn't seem to lose RPM on that machine but I wasn't paying that much attention to that, i just wanted to see the blower work, supposedly that only 2 more hp engine than my 14hp G5200. The lowest HP F-series kubota put this blower on was a 20hp.

SO far I've thought of these options (in no particular order):

Turn up fuel bolt. Not sure if this will help, if it's already blowing smoke i would surmise this would just make it blow more smoke. Some people claim 10% more hp, but not sure what they're basing that off of. Thoughts on this?
There is room to play with pulley sizes. On the blower, the PTO input is currently on a 6" dual v-belt pully. The upper driven pullys connected to the actual fan is 5.5" I could swap some pulley(s) to make it so it spins the fan disc a bit slower thought being reducing the net hp required. Pushing air goes up cubed as RPM goes up , so this could potentially help it quite a bit. I wouldn't get the full rated CFM from the blower, i dunnoo what it is but that blower will blow you over, so a little less is fine for my needs. Thoughts on best pully setups to reduce load on the engine?
Turbo the D600 motor. I find no "kits", but plenty of people have turbo'd their similar 3cyl kubota diesels with various turbo's out there.
Swap out the D600 motor for something a bit bigger in the series like 662 or 722?
]Get a g1800 or g1900
Call it the old college try and sell the debris blower.
Run it as is? Not sure that not getting full rpm and rolling coal under heavy load for a good period of time is good for the longevity of the motor.
Anything else I'm not thinking of?

Obviously options 3,4,5 will cost a significant amount of $$$$ and not sure it's really worth it. A g1900 would nice but finding the male quick front hitch that goes on the machine is a royal pita, they are almost non-existent and those with them tend to hold on to them. The pulley thing seems like it might work, but I'd have to really do alot of math to dial it in to that engine and am unsure if it will really work or not.

Any suggestions on things I can do to make it work for this G5200 D600 engine?

73blazer · Dec 10, 2019

Based on available data and assuming the lowest input needs to be 20hp (the lower hp machine kubota put it on...so the 20hp line is the base for all other numbers). ANd finding some formulas for hp/rpm/cfm relationships (it's cubic, meaning small gains in cfm require ^3 power more hp to drive). Here's what I came up with:

Code:

HP	RPM	CFM
30.10	3500.00	4354.94
27.60	3400.00	4230.52
25.23	3300.00	4106.09
23.01	3200.00	3981.66
20.92	3100.00	3857.24
[B]20.00	3054.00	3800.00[/B]
18.96	3000.00	3732.81
17.12	2900.00	3608.38
15.41	2800.00	3483.96
13.82	2700.00	3359.53
12.34	2600.00	3235.10
10.97	2500.00	3110.67
9.71	2400.00	2986.25
8.54	2300.00	2861.82
7.48	2200.00	2737.39
6.50	2100.00	2612.97
5.62	2000.00	2488.54
4.82	1900.00	2364.11
4.09	1800.00	2239.69
3.45	1700.00	2115.26
2.88	1600.00	1990.83

Meaning I'd need to get the fan speed down to 2700 rpm or so.
The d600 spins at 3200 or so I find, the pto pulleys on the machine put the pto output at 2800 rpm or so. ....more math for the implement pulleys (currnetly drive 5.7" and driven 5.2")...

Code:

New Setup	
        drive  driven in rpm      fan rpm
        5.20	5.70	2823.53	2575.85	(swap pulleys)
	5.70	5.75	2823.53	2798.98	Changing upper
	5.70	5.80	2823.53	2774.85	
	5.70	5.85	2823.53	2751.13	
	5.70	5.90	2823.53	2727.82	
	5.70	5.95	2823.53	2704.89	
	5.70	6.00	2823.53	2682.35	
	5.70	6.05	2823.53	2660.18	
	5.70	6.10	2823.53	2638.38	
	5.70	6.15	2823.53	2616.93

So for a 14 hp motor which my D600 is rated at, I need to spin that fan disk at somewhere around 2700rpm where now it spins at 3054 and not sacrificing a whole lot of cfm. . Which based on pulley formulas I'd need to either swap upper and lower pulleys on the blower..or get a ~6" pulley for the driven pulley on the blower and that would be enough to spin the fan slow enough for a 14hp motor. Math.....is awesome! I not sure I can swap upper to lower pulleys as I think the shaft dia.are different but I can certainly swap the upper out for a 6" and reduce the fan speed enough for a 14hp motor, or so the math tells me.So doing some pulley work it seems, so the math says, I can get all the cfm a 14hp motor can push.

73blazer · Dec 13, 2019

Well, math doesn't lie. I swapped those pulleys since that's free to try out so I can verify i'm on the right track. Works perfect! Engine is allowed to spin at it's full RPM, the fan disk is slower thus requiring less HP and no more rolling coal under the load. I'm probably on the low end now so I can swap one pulley out to dial it in a little better so I can get all the CFM a 14hp engine can put out!

aczlan · Dec 13, 2019

Awesome. Glad to see that you got it worked out.

Aaron Z

moship · Dec 17, 2019

Great! :thumbsup:

Now where's the video of it in action?

73blazer · Dec 17, 2019

moship said:
Great! :thumbsup:

Now where's the video of it in action?

I'm waiting on the driveline quik-coupler from Kubota. This came with a 15 spline coupler, my machine is 10spline. I had robbed that piece off my snowthrower for testing, but it's much longer, so no able to have it hooked into the quick hitch (securely) and use the d-shaft at the same time with that. Since the coupler was $75 I didn't want to order it before I knew I could get this working satisfactorily.

73blazer · Apr 1, 2020

73blazer said:
I'm waiting on the driveline quik-coupler from Kubota. This came with a 15 spline coupler, my machine is 10spline. I had robbed that piece off my snowthrower for testing, but it's much longer, so no able to have it hooked into the quick hitch (securely) and use the d-shaft at the same time with that. Since the coupler was $75 I didn't want to order it before I knew I could get this working satisfactorily.

Finally got this all working. Pully swap was the ticket. No more rolling coal, smokes just a weeee bit but about the same as when I snowblow...so..I think it's ok.
I had to do a dual relay setup with flyback diodes to do the chute rotator. I can use the same connection there to do my snowblower if I convert the manual chute rotator on that to an electric one.
Took it out for a little spin and did spring sticks/acorns/leaves/driveway dust.
Works really well.