More on fridge motors/compressors.

[tonyfoale]

Recently Sam posted about using a Fridge compressor as a vacumn pump at http://www.homemadetools.net/forum/h...ht=vacuum+pump

As well as these units being useful as they are, they contain nice little induction motors which can be useful in their own right.

Click on thumbnails for full size.



These pix show the motor with the pumping cylinder cast into the bearing housing. Note that the rotor is only supported in bearings at one end. The output shaft has a single sided crank to drive the piston. The other end of the shaft is extended and is tapered. It was a while ago when I extracted this motor from its case and I don't recall if that shaft and taper had any function. I don't think so and its existence is a mystery to me.

I had a project for a motor with a crank on (that is for a later posting here) so I cut the pump part off as shown below. That end face was milled flat for mounting.




Here is the tiny piston and conrod. the piston and its cylinder are both made in grey cast iron and so are very much self lubricating. When I used this as a vacumn pump I never added any oil which is contrary to the advice given in the previous post. When I extracted the motor and removed the piston there was NO sign of any wear. The crank is also made in CI and there was no wear on that either.

[metric_taper]

The other end of the shaft is extended and is tapered. It was a while ago when I extracted this motor from its case and I don't recall if that shaft and taper had any function.

I believe that taper, is an oil pump, it rotates in the sump of oil, and centrifugal forces of the oil in the hollow shaft brings the oil to the top of the hollow crank shaft, where it slings out to lube the con rod via an oil gallery, and the piston.

[toma]

As I know, these motors are sunken in freon, or something similar, so they are cooled and lubricated automatically...

[hemmjo]

As Toma mentioned ... When these compressors are used in a refrigeration application, as designed, some oil is circulated with the refrigerant to cool and lubricate the motor and compressor. This is why the oil must be compatible with the refrigerant. Depending on the design, in most systems, when in use, the top of a compressor is warm/hot, while the bottom is cool/cold.

In an air compressor application, as mentioned in the other thread, the bottom is also warm since there is no cold refrigerant vapor entering to cool the oil and motor.

John

[metric_taper]

No, compressor "cans", have oil that is at the bottom "sump". Refrigerant does cool the compressor, as the cool suction gases enter at the top of the compressor can as vapor, and this is required for motor cooling. The discharge line is from the compressor outlet via tubing to a header, where it exit's the can. Oil typically circulates through the system. Some systems have oil separators in the discharge line to return most of it to the sump, but this is mostly in very large systems, and where the compressor type (e.g. scroll, roots blower) pump more oil to prevent metal to metal wear, as well act's as a seal.

[tonyfoale]

I believe that taper, is an oil pump, it rotates in the sump of oil, and centrifugal forces of the oil in the hollow shaft brings the oil to the top of the hollow crank shaft, where it slings out to lube the con rod via an oil gallery, and the piston.

I checked mine and can confirm the truth in the quote, except that it is not the taper that is the pump, it is the eccentric nature of the crank that is effectively the pump.

[marksbug]

the shaft is supported on both ends of the motor just only 1 end where the piston is. many engines are also only supported on 1 end. small tillers have a 1 peice rod with a caged/housed needle bearing in the steel plate conecting rod, it just slips over the throw and away it go's. take off the cylinder and just pick upward on rod/piston/cylinder assy and off it comes. that compressior has much more rod than those engines do. there are many different oils that refrigeration uses. some much better than others.and some even help cool you down better..witch saves power.runs less last longer. this is the first one of these Ive ever seen, now I know how they work,I want to see a scrool all appart, all Ive seen is drawings that are crap and cant tell squat.Ive been told a few different ways they work...I think they are all rong.

[Philip Davies]

This is the OUTSIDE! (Modified.) ( Modified by heating and beating it a bit) Bloody awful job getting that motor out.

[madokie]

oh its not that bad,i scrap these all the time,,just use a 4 1/2 inch angle grinder with a thin black aluminum /oxide cutoff wheel, let the wheel cut at its own pace,try to use a 1/4-3/8 length of the wheel to do the cutting instead of the side of wheel which is 1/16 and wheel will last longer,.cut off the top, drain the oil inside , and dissasemble,,,dont use those diamond wheels for anything but thin guage sheet steel,,they will load up with AL, brass, copper and even steel and then be useless,,the diamond wheels like to skid all over ,making it hard to get a cut started,,the AL/ox wheel will dig right in,, i buy the cheapest ones off e-bay,, 50 f 25$...040-.045 thick, the dewalt one that LOWES sells are .055-.060 thick, made in canada or europe,they do last longer and are less apt to break while using, but cost 3 -4 times my 50 cent ones,yet only last twice as long,,be carefull and the cheap thin ones work just fine...ALWAYS USE A GUARD !!!!!!! ALWAYS WEAR SAFETY GLASSES !!!!!! #1 scrap copper is up to $2.95 a pound !!!!! WOHOOO!!!!!!

[marksbug]

Ive never been able to get this abrasive fiber disc to cut squat. I might be defective.