Oliver Hart-Parr 28-44 thrashermans special?

Hey guys this is my first time on the forum I just bought a 1936 oliver hart-parr 28-44 serial 507991A-C33 I'm trying to find out what the C33 means the guy I got it from said it is a thrashermans special it has a huge belt pully on it hand throttle on the fender and a pintel style drawbar in the rear it also has a 4 speed trans if anyone has any info it would b greatly appreciated I'm haveing a tough time finding anything about the thrashermans special option I've found old ads with it mentioned but no real way of knowing if mine is
Thanks
AM
 
C-33 is a code number for the transmission/ final drive set up. I will need to get my old book out to get the specific variation. You have a phone number or e-mail? J.
 
My ollie90 is designated C66 - the high speed top gear. The C33 was the default lower speed top gear.

The early models were only 3 speed? Not sure about that, or some had top gear locked out (those on steel only?)

The later model 90 did not have the gearing suffix, unless it was not the usual one fitted at the factory.

JS will probably give the full story. Hope he posts it on here so we all learn.
 
There were at least two different 28-44 special tractors. One was called a thrasherman special, and the other was called a High Compression special.

You need to direct your research toward the High Compression model.
 
From Wendel:
'By 1935 ... also available as a Thresherman's Special with cast disc front and rear wheels. High speed and low speed versions were available, as was a special high altitude model'
 
OK. More info extracted from Nebraska Tracto Tests (Wendel, again).

28-44 was originally 3 speed, as I thought. Presumably, before it metamorphosed to the Oliver 90, they introduced the 4 speed box and these would be the options (or recent
development from) over the 'standard' three speeders - hence the gear designator suffix on your tractor?. The C33 and C66 gear boxes were clearly continued into the 90 range
where the C33 was the standard set of ratios supplied, so not suffixed on the serial number. The C66 only had a different top gear ratio, I believe (not checked it out from my parts
books), and there may have been other gear sets available.

It may be possible that some 28-44 tractors were fitted with the four speed box but with the top locked out, if supplied on spade lugs. I have only been told verbally of the locked
out top gear, so it may not be fact. I have not seen it mentioned in print. The man, who told me that, actually worked the 28-44 tractor in the UK.
 
I am a little confused on several things. The suffix letter A indicated the tractor has the high altitude engine. Now here comes the confusing part.C-33 is used to designate a 28-44 special. On a 90 or 99 the regular speed combination is listed as a C-33 but is not normally added to the serial number. However on a 28-44 tractor C-33 designated a 28-44 Special. On a 90 or 99 the regular speed combination is also designated as C-33 and it is not added to the serial number. The sticky part is no 28-44 tractors had a 4 speed forward transmission. Now does the tractor have just a parking brake or does it have axle brakes? Oliver 90 owner mentioned the heavy cast front wheels. I knew a guy that had one of those tractors with the heavy front wheels. Does your tractor have those? What is the size of the rear wheels? Your turn and check that e-mail address. How about a phone number? J.
 
email should be right but u can text me at 5407057773 mine is on rubber with heavy cast centers front and rear the rear are probably 6"+ thick and have oliver cast in the side of them only has a park brake no steer brakes it has L,2,3,4,R cast in the trans cover it appears to be all original and not pieced together like some I've seen it has a factory looking hand throttle on the right fender it has an eye style hitch instead of drawbar the beltpully is huge tho I haven't measured it yet I'm guessing it probably almost 20" across
 
23434.jpg
 
I am thinking your tractor was, indeed, part of the transition of HART PARR oliver to OLIVER (dropping the Hart Parr bit).

Your radiator is cast with OLIVER, but the earlier 28-44s were cast with HART PARR with oliver underneath as a minor part. You can see this if you go to 'goggle' images and search
under 'hart parr oliver 28-44'.

I am now wondering which magneto, governor and carburettor your engine is fitted with - the early 28-44 items, or the replacements/improvements used for the 90 series. The
springs for axle articulation limiting are 28-44 (they changed to solid stops on the 90s).

The plot thickens? I've never seen a fender mounted throttle, only the under-steering-column rod variety. But I doubt many (if any) Thresherman's versions arrived this side of tne
pond!

Belt pulleys were listed as 16 3/4, 13 1/2, 14 1/4 and 19 3/8 inches in the original parts book for my '48 ninety. Parts book is dated June '47.
 
oliver90owner
Not shure how to add u on email tho I thought i set it up so people could see mine I'm new to this forum thing my email is [email protected] my 28-44 has a ensign carb the mag is wrong it has an American Bosh but is one of the late replacement ones my mag man says he believes it should b a U4 and the gov is on the right side with a rod running through the block to the left side it has HART-PARR cast in the block in big letters and on the radiator in small letters under oliver also says it on the serial tag
 
The basic engine design was used from 1930 to c.1952. In or around 1937 the Hart parr name was dropped and the company was known, from then onwards, as the Oliver
Corporation.

I would expect the hart parr was simply machined off the engine casting patterns and changed on the radiator header tanks.

I think the early governor was called a constant speed governor whereas the later was a true variable speed one.

The ealier mag was base mounted, but the later American Bosch MJB 4A was flange mounted to the governor housing. All engines had the shaft through the
block from governor to the carburettor connection. The Ensign carb was replaced by a Schebler on the 90/99. Either a TTX-21 or TTX-22 depending on model.

It would appear that these specials were likely introduced to use up older components while introducing the new upgrade parts - quite a common ruse back then, it seems. Things
like water pump lubrication and seals were changed at various points along the way, as was fitting a thermostat in the much later 90s. I still have the old water manifold which was
changed for one with a thermostat (my ollie 90 is a 1948 model). Early water pumps were greased and adjustable packing glands were utilised, but later ones had a carbon seal
arrangement and oilite fan bearing bushes lubricated from an oil line from the head.

They were a good dependable engine, I believe. Weak points were governor housing oil feed and valve heads coming adrift - mine suffered both these faults during its working life.
I know the full ''service history'' because my Dad bought it new in 1948.

RAB
 
Just to add one other odd model to the mix is this Oliver Special. It is the model just prior to the Oliver 99. it has the four speed, generator and lights and a high compression head.
23486.jpg
 
Centerplate
From what I can see in the pic that looks almost identical to mine same generator/mount looks like the same belt pully mine doesint have lights and it has heavy cast wheel centers front and rear but other then that what I can see looks right
 
(reply to post at 05:26:15 06/27/15)
The suffix on your tractor should be AC33 which would indicate a high compression special, I believe. Did this tractor come from Virginia?

Jm Call
 

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