Date: Fri, 7 Oct 2011 08:31:48 -0700
Reply-To: Poppie Jagersand <poppie.jagersand@YAHOO.CA>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Poppie Jagersand <poppie.jagersand@YAHOO.CA>
Subject: Re: Diesel starter differences,
Was Re: Starter motor do-it-yourself rebuild
In-Reply-To: <1314049602.76258.YahooMailNeo@web45301.mail.sp1.yahoo.com>
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Some more notes in this "all about the Vanagon D starter" thread.
Had a dead starter again. This time the solenpoid it appears. On my "home rebuilts" I disassemble the plunger part of the solenoid, clean, and very lightly grease (too much grease and the plunger seals against the barrel and sees "compression", so it won't pull the gear.) However I don;t do the contacts, which are more difficutl to get at. Here's a document on the solenoids for those who are interested:
www.venselenterprises.com/...files/solenoidrebuildingarticle.pdf
I had an extra used solenoid so swapped that one in instead. Then I'll go to my rebuilder to ask if he has any more used or rebuilt solenoids.
The broken solenoid also allowed me to measure the "pull" current. This is the normally very brief current which is only drawn for a subsecond while the plunger moves. Since my plunger never closed the contact the pull current remained on as long as the key was in cranking position. 10s or so of "on" caused smell/smoke which made me curious. Turns out pull current is 30A. This is ok instantaneously but pretty high for the wiring and spade connectors used if continuous. Normally when the plunger closes the pull coil is turned off and a smaller hold coil is left on holding the contactor and starting gear in position. This is the aspect that didn;t function on my solenoid.
Now for some questions:
On the newer, gear reduction starter, I was wondering if the rear motor part is shared between several Bosch starters? If so it would be possible to mate the motor part from a more common Diesel car starter to the Vanagon nosecone. Does anyone know what car models might be candidates? This could also be explored experimentally at a rebuilder patient enough to allow some roaming around in his boxes of old cores.
Along this vein, I have a vanagon starter nose cone from the newer starter, but with a broken and snapped stud in it. It is a pretty thin (M6 or smaller I think) hard metal alloy stud screwed into the alu nosecone. Anyone has tips on getting it our w/o damaging alu casting?
Finally some more info addressing the two variations of starters in the previous post below:
I weighed both the origonal direct drive (DD) and the newer gear reduction (GR( starter.
Weight
DD starter 8kg
GR starter 4Kg
Now some basic thermodynamics tells us that 8Kg of iron and copper can absorb twice the heat of 4kg, suggesting the old starter can crank quite a bit longer than the new (e.g. for those of us who prime the fuel system by cranking rather than using a vaccum pump). A very rough estimate is that the old starter can take 2-3min cranking, while the new one one should probably keep cranking to 1min or less. This was arrived at by putting 1kW into a motor simulator for a motor of similar weight and having it calculate the overheat time, so not very accurate, but maybe a rule of thumb.
Martin (and '82 Westy 1.9TD "Poppie")
----- Original Message -----
From: Poppie Jagersand <poppie.jagersand@YAHOO.CA>
To: vanagon@GERRY.VANAGON.COM
Cc:
Sent: Monday, August 22, 2011 3:46:42 PM
Subject: Diesel starter differences, Was Re: Starter motor do-it-yourself rebuild
A note for all users of the Diesel starters:(not just rebuilders)
The smaller newer gear reduction starter is likely more electrically efficient. It is also likely much cheaper to build.
However an advantage of the old, heavy direct drive starter is that it is much more abuse tolerant:
*The heavy weight makes it take much more cranking abuse before overheating.
*The construction is more durable. No flimsily attached and very fragile ferrite magnets.
*Fewer parts so less than can break.
So don't toss your old heavy original starter. Keep it around for when you get tired of replacing those new aftermarket (or Bosch) starters, and either rebuild it yourself, offer it to a listmember or find one of those (now rare) shops that will actually rebuild your starter, not just give you a replacement.
Martin (and '82 Westy 1.9TD "Poppie")
----- Original Message -----
From: Poppie Jagersand <poppie.jagersand@YAHOO.CA>
To: vanagon@GERRY.VANAGON.COM
Cc:
Sent: Friday, August 12, 2011 10:38:02 AM
Subject: Re: Starter motor do-it-yourself rebuild
Here are some more starter observations. I pulled apart and compared the two different types currently available for our Diesel vanagon. As Neil, Bryan and others have noticed, when you get a rebuild you may end up getting the smaller swapped for the larger and vice versa.
member NYSwanderer put some photos on the web, and wondered what the differences between them are.
http://groups.yahoo.com/group/Diesel-Vanagon/photos/album/1381430081/pic/449269473/view?picmode=&mode=tn&order=ordinal&start=1&count=20&dir=asc
I took them apart and here is my side by side comparison:
The smaller is a gear reduction starter using a planetary gear and has a permanent magnet motor. The larger one is a direct drive motor with windings in both stator and rotor connected in series. Both AFAIK meet spec.
I have a torque/power graph for the smaller one from a rebuilder.
If someone got a graph for the bigger it would be interesting to compare. Please scan and email me and I'll post both.
In theory the larger starter could have both a higher peak torque and a higher max rpm. That comes from the fact that both rotor and stator windings are connected in series. When stalled or at very low rpm, the high current will increase the magnetic field in both the stator and rotor. By contrast, the permanent magnet motor has a fixed magnetic field from the ferrite magnets (that may even go down if the starter gets hot).
For the series motor as the rpm increases the magnetic field weakens. This field weakening yields a lower back EMF in the windings, and thus allows for a higher RPM.
These are differences you learn in a motor text book. The gear reduction and design of the smaller starter may very well make up for them. That's why it would be interesting to compare test graphs.
Mechanical differences:
I don't think many internal parts interchange. I tried to use the studs from one on the other, but threads were different. Brushes and brush holders are different.
At best there seems to be some chance that solenoids and end bushings may be the same, but I need to check. Or someone with Bosch data tables can find out.
The smaller one have very brittle ferrite magnets. Don;t drop your tools or they can/will shatter. The bigger one has robust copper windings in the stator.
Another note on the smaller starter: nyswanderer remarked that he saw no Bosch markings on his, so it must be an aftermarket. I however got a smaller starter that a friend had brought from Germany. That is an original Bosch with markings. I got another one with no markings.
Martin (and '82 Westy 1.9TD "Poppie")
----- Original Message -----
From: Martin Jagersand <jag@CS.UALBERTA.CA>
To: vanagon@GERRY.VANAGON.COM
Cc:
Sent: Saturday, August 18, 2007 9:12:00 PM
Subject: Starter motor do-it-yourself rebuild
I just rebuilt the starter for my '82 Diesel Westy. Last time I did it was
in '99, I think, so the previous rebuild lasted about 8 years.
Bosch rebuilt starters can run near $200 nowdays, but rebuilding it yourself
is not hard. Here are some tips:
(Edit 2011: I was quoted from 200 to $400 for a Bosch rebuilt, $100 to 300 for others)
First check that the problem is really the starter. Measure the voltage over
the starter itself while cranking, ie from the positive iput terminal on the
starter to the starter housing. If it's 8-10V and the starter still is
cranking slowly the starter is most likely bad. If battery voltage is ok but
voltage at starter is low check voltage drop in the positive and negative
circuit. When I measured I had .2V drop in the neg circuit and .9V in the
positive. Of the .9V .7V was over the solenoid and .2V in ther actual cable.
If it is not starting at all, no noise, no click, despite having 12V at both
starter and solenoid, check connections to the solenoid, and then between
solenoid and starter. This time I found that the metal tab running from the
outside of the soloid terminal and connecting the solenoid winding was
sheared off. I soldered on a flat piece of copper (from a water pipe ground
strap) to fix it.
So you determined that its the starter. All Bosch starters, gas or diesel
have the same basic design, but the sizes and housings are different between
different models. Get the right parts!
Wear parts are basically:
1/ Bushings: 3 total. One in each end, and one in the middle. The latter I
don't think carries much load. Cost: about $1 each from the Bosch
distributor.
2/ Brushes: 4 in total. You can buy either a brush assembly for $45 with the
4 brushes already mounted, or 4 loose brushes for about $15 total. If you
get loose brushes get ones with small u-shaped metal ends welded to the
copper braid. They are much easier to solder to your brushholder.
The above is Bosch prices VW dealer prices are about twice as much.
Rebuild procedure:
1. Unscrew the two small screws on the commutator housing (back) this
releases the brush holder.
2. Unbolt the two studs in the back. Now the commutator end comes off after
removing a circlip on the end of the shaft, and the rotor is loose, but
don't pull it off yet.
3. Loosen the 3 screws holding the solenoid to the front housing.
4. Between the solenoid and the starter motor is a small rubber piece. See
if you can loosen it. Carefully wiggle and separate the front housing.
5. Solenoid and starter can be separated at the solenoid end. Take off the
solenoid. (To prevent binding wipe off any dirt or corrosion on the solenoid
plunger before reassembly)
6. Determine shape of bushings. The gear end bushing is in the bellhousing
on starters for transverse engine models, and in the front housing on
longitudinal engines. Replace front and rear bushings if worn.
7. To get at the middle bushing remove the ring and c-clip in front of the
gear. Slide off gear assembly. Take out plate holding middle bushing.
Replace if worn.
8. Check brushes. New brushes have about 8mm between the tip and the copper
braid. I'd replace them if they are more than half worn. Also if the
bushings were really bad the starter shaft has been riding out of center,
and the brushes have been wearing irregularly and need replacement.
9. Snip off the braided copper holding the old brushes. Don't lose the
springs! File off any remains from the brush holder. Solder on new brushes.
Make sure they are soldered well. Each brush will pass 100's of amps at
startup!
10. Inspect the commutator. If pitted (from arcing) sand/file down until clean and smooth
copper. If out of round use a lathe.
11. Assemble the parts. Grease bushings and gears lightly. You don't want
grease on the commutator or too much so that it can spatter on the clutch.
--
Martin Jagersand
University of Alberta
http://www.cs.ualberta.ca/~jag/
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