Help with a hoover 700 motor.

[seanbar1089]

Hi!

I've worked on electric fans and restored old GEs so i do know about AC motors. I know DC is different are uses carbon brushes but I haven't worked on them too much. Usually the vacuums I've restored are color coded in some way and the brushes are in better shape or do not need to be removed ot be rewired or restored.

Right now im attempting to rewire a hoover model 700 motor. I could not test the machine when I got it because the cord from the motor housing was in such bad shape that I had to wiggle the wires to even make sure I got resistance on my multimeter before I bought it and left. The resistance when I started and got in was about 13 ohms or so.

I took it apart and started cleaning it yesterday. The oroginal wires leading to the bail plug snapped off on me before I could see what leads went to what. I cleaned up the commutator and got as much of the old carbon dust out of the motor housing as I could. Then I started rewiring. I did one wire at a time as to not confuse any wiring. I also downloaded the service Manual from the 1950s that had all the old service info in it dating back all the way.

I put it all back together except for the fan blade and blade screw. I put the old carbon brushes back in attempting to put them back in the same holders in the same way. I wired the two leads to the bail plug. After that,I plugged it to a serge protector then I turned the serge protector on.

It runs. It run,extremely fast. I'm not letting it get up to full speed I have a lot of arching (sparking) on the armature where the carbon brushes are.

The motor runs clockwise. I'm not sure if its supposed to as when doing a basic search on vacuum motors, there is info thats says it's supposed to run counter clockwise.

I switched the leads from the bail. It's still runs clockwise.

Now the motor reads somewhere between 10-12 and sometimes 13 ohms depending on when I turn the armature. There is some carbon build up on the armature again


I'm just kind of frustrated and confused at this point. I'm not sure if these old hoovers are polarized and I don't know how to check that when the wires on these old vacuums are the same color when I open them. Is there a way I can test that on my multimeter?

I don't know if I'm seating these brushes wrong and,if so, how should I fix it? I do know of a product called a carbon brush seater. But Im not sure if its going to help.

I don't want to burn this motor out. If there's another reason that you can think of, please let me know. Also should the motor be running clockwise or counter clockwise?

Below I have a few pictures of the armature and carbon brushes assembled. Feel free to ask om you need any more information.


Any help would be appreciated.

Thank you!

 

[lesinutah]

Id

Use new carbon brushes if your cleaning off commuter.
I'm not very well versed with the hoover motors. I had a coil going bad and it caused problems.
I'd make sure you get it spinning the right way. I'd take it to a vacuum shop. They could probably help ypu more.

 

[repairman]

If the arcing goes around the circumference of the commutator, then the armature is likely toast. It's easier to tell if I saw a video. As for the speed thing, you're running the motor unloaded. You need to have the fan attached for it to run at the proper speed.

 

[seanbar1089]

Thank you for the responses. Lesinutah, I am in the search for new carbon brushes right now. I went down to ace hardware, they only have ones for power tools and none of them are really the correct sizes. The ones in there are almost 6x6mm high and wide.

There are some on Amazon but they are mostly for tools so I'm not sure if they are going to work. Here is a link

https://www.amazon.com/dp/B0CGXCDXL...=1&sp_csd=d2lkZ2V0TmFtZT1zcF9waG9uZV9kZXRhaWw


Repairman,it is not arching around the circumference. Just where the brushes are. One is arching more than the other.

I have a video that I can send you via email if you want me to email it to you. Right now the best way to get in contact with me is [email protected]. I attached a picture but it doesn't show you as much as the video will.

I was testing it with the fan off because,I was following an online video on YouTube of someone restoring a hoover 750.



If you think it's going to hurt the motor, I will stop, I just wanted to run the motor for this test it befe or put everything back together for adjustment sake.



Thanks,
Sean.

 

[mjhoshaw]

Running unloaded

Fortunately motors of this era run much slower than today's, so IMO it is unlikely that running unloaded briefly will damage it (and the video seems to bear that out.) I determined that the fundamental frequency (pitch) of the motor in the video on high is about equal to F below middle C, which translates to 175 Hz and change. That * 60 seconds in a minute = 10,500 RPM, pretty sedate by today's standards. I wouldn't dare do this with a modern motor, which runs between 30,000 and 40,000 RPM under load.


 


Motors like yours are called universal because they will run on AC or DC. On both AC and DC, the motor will turn the same direction regardless of how you connect the power source. To change direction would require you to swap the field coil leads going to the brush holders. Swapping the bail wires will make no difference.


 


The sparking visible in your still image may not be optimum, but it doesn't look worrisome to me. Big fat yellow or orange sparks or a ring of sparks as mentioned previously would cause me concern. A brush seating stone probably will help. A small amount of sparking is always normal in brushed motors. A thin film from the brushes on the commutator is also normal, and it is what permits the motor to run at the speed it does without quickly wearing out the brushes. The brushes are not pure carbon; they often include graphite, which is very slippery. This thin deposited film lubricates the commutator and reduces friction between it and the brushes, but being made of brush material it's conductive and doesn't interfere with operation.


 


I hope this helps. Best of luck with your 700! I had one in the mid '90s and it was a real pleasure to  own and use.


 


Cheers,


 


Joel


 

 

[lesinutah]

Hey

What is the height and size of the brushes you have. What the height and size of the carbon brush housing.
The Amazon brushes fit the kirby heritage and that motor is bigger than the hoover 700. The Amazon brushes won't fit.
I looked in my 1951 blakeman parts book. The carbon brush number was x21v. The carbon brushes were in early royal tank vacuums.

 

[bikerray]

The original Hoover number for the carbon brush was 4747
Carbon brush size 1/4" X 9/32" X (approx) 3/4"

If you're looking at the motor from the top the fan would be spinning Counter Clockwise
If you're looking at the motor from the bottom the fan would be spinning Clockwise

Here's a hint look at the way the fan blades curve, since they are made to blow air out they kind of tell you which way the motor rotates.

 

[seanbar1089]

I appreciate the help you guys are giving me. I actually disassembled the motor and took the housing out and measured it. However, I did so in millimeters instead of inches. The housing it was about 8 mm across and wide (so almost 3/8 of an inch).


Mjhoshaw, in the video the sparking looks like a tiny marble of light in which is extremely bright and almost blinding. I decided to buy a carbon seater stick.
I apreciate the good luck. I'm new to vacuum collecting and fixing. Got the bug when I saw a headless duel sanatronic 80 at a thrift store. I put a lot of work into it, and now love using it. Then I had to get an electrolux, then a hoover, then anotherc electrolux and another hoover and another 2 kirbys. Lol. So I'm glad I'm in good company.

Bikerray, I apreciate you letting me know about the rotation. I just overthought it a bit. A few years back, I wired a antique fan wrong and the fan started going backwards and was not very happy. I think it ended up blowing out the motor. I also heard when motors go bad sometimes they go backwards so I wanted to double check myself and ask.

I don't know where I could find replacement carbon brushes with that specific 4747 hoover number.

I was wondering if I could use ones with almost the same dementions.

Either these

https://www.ebay.com/itm/232921364290

Or these

https://www.ebay.com/itm/2321702440...xKPahM6bCQDIktKjTxQn|ampid:PL_CLK|clp:2332490


If I do get replacements like these, should I replace the new coils with the originals?
What if they have the long cord going from the brush through the coil?

I'm planning to call some sew and vacs in the area to see if I can locally source them if these ones online won't work for the motor. Or if I can get any information on where to source some.
If anyone has any ideas where to source originals, please let me know.

Thanks,
Sean

 

[lesinutah]

Part number

Your probably not going to find hoover brushes with the part number.
The second set of brushes will work.
Leave the coil.