Could a guy that has a PTO SM420 just do some shaft turning and rotation counting?
I don’t recall from memory how much the shop manual has to say about the PTO. There might be a grainy pic of the gears themselves that one could do some math.
From what limited information I can find, there were (are) many ratios available. If I limit my search to 6-bolt PTOs, the closest to 1:1 I can find in modern documentation is a 2:1. Most appear to be 4:1 or 8:1. I am still having trouble determining compatibility on those though.
The pto ratio depends on specifically which pto is mounted to the transmission The input shaft is about 20 teeth The intermediate shaft is about 40 teeth That gets you to 1/2 engine speed The intermediate shaft presents about 33 teeth to the pto gear I studied a photo of one of my pto parts and it looks like it’s about 24-26 teeth So the pto is doing about 60-70% of engine rpm This is anecdotal data But usually the pto is slower than the engine I would not recommend exceeding about 150 ft/lb of torque or maybe 10-20 HP into the pto input without doing a more thorough study of the forces involved, maybe it could handle more but I don’t know if the original tiny thin pto casting could do it, might pop off, that’s how they fail when you forget to disengage the pto and drive down the road with too much torque on them.
Enclosed is picture of 420 Chelsea PTO, cannot read MN. Some numbers visible on casting. Bronze or brass bushings, 26 teeth. Not sure bushings would stand duty required for an alternator/generator!
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires. '47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle. '54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed. '55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
Looks like that PTO is a 0.86 drive ratio and rated for 225 ft-lbs intermittent use (defined as 5min per 15min interval).
The motor I am looking at is 70ft-lbs of torque up to 2000rpm. With that drive ratio, that would be 60ft-lbs up to 2300rpm. That is comparable to the torque of the hybrid system that GM put in suburbans in the early 2000s and it would push them up to about 20 (supposedly 35, but I have found a lot of evidence that it was not that strong). This truck weighs about 1/3 of a modern suburban with the aero of a brick, so I would expect at least similar performance.
I agree that the bushings look like the weakest point. It would probably be prudent long term to replace them with real bearings. That starts down a long and potentially endless path of strength upgrades.
Last edited by Fibonachu; Tue Jan 24 2023 08:42 PM.
Since you would need to do some metal machining work Maybe attaching your motor directly to the drive shaft at the output of the transmission with a 2:1 ratio chain drive would be more ideal Saves the pto for pto things And fixes the rotation intermediate gears issues and clutch and Pilot bushing possible wear issues. Find a transmission with the brake drum and swap that for a big chain gear. 2:1 on the drive shaft multiplied by the rear end ratio gets you at the typical motor to wheel ratios of all the modern electric vehicles on the road today, 5.x-8.x typical. -s
To replace the bronze bearings with roller or ball bearings would require a whole new housing. The bearing retainer area is very thin, strong and thick enough for existing use, not for larger bearings.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires. '47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle. '54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed. '55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
Another thought would be to attach a 4wd transfer case on the back of your 420(Novak makes an adapter), so something could be driven off the extra(front) output that could be controlled separately from the truck driveshaft.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires. '47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle. '54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed. '55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
Don't do it. Nobody else will say it. I don't really mean it. Just giving you an out if you wanted to take it. (Anyone on this site who knows me personally will tell you that, above all else, I am best known as a giver.)
So i have been thinking about all the suggestions on this..................
If one were able to do the following I think it would be a win:
1. Electric motor will be attached to the DS at the tail of the transmission. Whether the DS goes through the motor or it has some type of gear chain attachment i don't think matters. 2. Have a connection like a MC starter does. Don't know the techy name for it, but it grabs one way to crank engine, then when engine moves faster it releases. If you want regen braking do away with this idea. 3. Electric motor will be activated with a POT on the gas pedal. That way when you shift it pauses as well. 4. Pick the amount of HP and battery life you want. 5. Find a guy smarter than I am to figure out the details of this, but I do think it would work.
1966 C-10 Step Side. 283, 4spd, 3.73 gear. 60K miles prior to restoration. 507 Paint Code. Currently in 10,000 pieces, but it's starting to go back together. Rear Suspension is done! Wheels are done! Bed bodywork is done! New 383 and TKO 5 speed in place.
