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Lucas DR3A wiper - conversion to 2 speed


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Hi Guys,

Would it be possible to substitute a field coil and back plate from a Lucas 6WA 2 speed wiper motor as used on Hillman/Sunbeam cars which had the same shape field coil, to a DR3A and make it 2 speed. I have several 6WA motors under my bench as spares for my Sunbeam Tiger.

It seems physically possible, I think it's just the wiring internally and the way the 3 wires a brought out?

Thanks

Rich 

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I make two-speed replicas all the time.  I often have one listed on eBay. I've made quite a few using the NOS B90 service spares.

You want a resistance of 10 Ohms in series with the field coil.  You can do this with a fixed resistor that can handle 5W.  Or like Lucas you can overwind with resistance wire.

A fixed resistor will cost less than a pound.  A coil of resistance wire more like £20.

I swap the end-caps as you suggest.  But there is no need to do this.  It's just appearance.  You can just make a small hole on the end cap and bring out one extra wire.  I did the same thing in CRT motors for TR2's. Worked fine.

A Lotus Elan motor used an external rheostat to get continuously variable speed.  But a fixed external resistor would be more reliable.

Don't exceed 10 Ohm.  As you weaken the field it reduces the torque and you may have difficulty starting up.

6WA motors are getting very scarce and Maserati and Ferrari owners are paying a lot for them, I should think twice before breaking one.

Oh I forgot to say that the cut-out for the wires on a 6WA maybe in the "wrong" place and there may be a thermal cut-out, neither of which matters very much.  You will need good soldering skills though because there is not much room in there for the wires.

 

 

You will of course need to find the correct switch.

Edited by AlanT
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2 hours ago, AlanT said:

I make two-speed replicas all the time.  I often have one listed on eBay. I've made quite a few using the NOS B90 service spares.

You want a resistance of 10 Ohms in series with the field coil.  You can do this with a fixed resistor that can handle 5W.  Or like Lucas you can overwind with resistance wire.

A fixed resistor will cost less than a pound.  A coil of resistance wire more like £20.

I swap the end-caps as you suggest.  But there is no need to do this.  It's just appearance.  You can just make a small hole on the end cap and bring out one extra wire.  I did the same thing in CRT motors for TR2's. Worked fine.

A Lotus Elan motor used an external rheostat to get continuously variable speed.  But a fixed external resistor would be more reliable.

Don't exceed 10 Ohm.  As you weaken the field it reduces the torque and you may have difficulty starting up.

6WA motors are getting very scarce and Maserati and Ferrari owners are paying a lot for them, I should think twice before breaking one.

Oh I forgot to say that the cut-out for the wires on a 6WA maybe in the "wrong" place and there may be a thermal cut-out, neither of which matters very much.  You will need good soldering skills though because there is not much room in there for the wires.

 

 

You will of course need to find the correct switch.

I read somewhere in a 1950s ad, I may have got it wrong, mind, that two-speed TR2 wipers were available as an optional extra. If so, was it the same casing? In AlanTs guidance notes I read that the 2-speed was already available for some British makes by early 1950s. 

Or does the body and model have to be a TR3A one to work?

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Hi Alan,

Ah that's interesting. So I can convert an existing DR3a to run 2 speeds by just adding a 10 ohm resistor. Where to get one? Can you possible supply a wiring diagram for the work to be done please.

I have 3 fully working 6WA's sitting on my bench at the mo, all stripped., cleaned and working well.  Also 2 x  6WA drive units with wheels. What would they be worth then? 

Thanks Rich

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Any model that does not have permanent magnets for the field will work.  Even the weedy little CRT model from a TR2.

It's just a bit more difficult if you want it to look original.  The factory abandoned the push-on terminals and went over to a flying 3-wire cable for two-speed models.  This used a different type of end-cap, actually from the Jaguar motors that have 6-wires.

But you can stay with push-on terminals and just bring out one extra wire.  If you were to convert a TR4 this would be a good way because you would not alter the wiring loom.  Just take an extra wire to the correct type of switch.

The two problems are finding resistance wire and making soldered joints to it.  That's why I started by using 10 Ohm resistors.

Wire-wound resistors like that can be bought easily, many sources on eBay and other big suppliers of electronic parts also.

To value a 6WA just look at past sales on eBay, I sold a couple last year.

2speed-mod-4.jpg

Edited by AlanT
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3 hours ago, rvwp said:

Hi Alan,

Ah that's interesting. So I can convert an existing DR3a to run 2 speeds by just adding a 10 ohm resistor. Where to get one? Can you possible supply a wiring diagram for the work to be done please.

I have 3 fully working 6WA's sitting on my bench at the mo, all stripped., cleaned and working well.  Also 2 x  6WA drive units with wheels. What would they be worth then? 

Thanks Rich

Hi Rich,

Ebay  https://www.ebay.co.uk/itm/2-Pcs-Aluminum-Case-Resistor-5W-10R-10-Ohm-Wirewound-For-Led-Replacement-Con-PF/313037048323?epid=20028998116&hash=item48e2764a03:g:rF4AAOSwcIpeeifM

 

Roger

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7 hours ago, AlanT said:

Any model that does not have permanent magnets for the field will work.  Even the weedy little CRT model from a TR2.

It's just a bit more difficult if you want it to look original.  The factory abandoned the push-on terminals and went over to a flying 3-wire cable for two-speed models.  This used a different type of end-cap, actually from the Jaguar motors that have 6-wires.

But you can stay with push-on terminals and just bring out one extra wire.  If you were to convert a TR4 this would be a good way because you would not alter the wiring loom.  Just take an extra wire to the correct type of switch.

The two problems are finding resistance wire and making soldered joints to it.  That's why I started by using 10 Ohm resistors.

Wire-wound resistors like that can be bought easily, many sources on eBay and other big suppliers of electronic parts also.

To value a 6WA just look at past sales on eBay, I sold a couple last year.

2speed-mod-4.jpg

Two questions for you.

1. Presumably, an early 3 will be fitted with the same weedy TR2 wiper motor?

2. If one weren't fussed about originality, would there be cheaper, more modern alternatives that would work? And, if so  which ones? And finally, how much would they cost, judging from your experience?

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Hi David,

the rack and fitting onto the tubing look similar for all the motors so it is quite possible for the TR6 14W motor to fit.

You would need a new mounting, adaptor loom to existing loom, and a dedicated switch - all for less than £100

 

Roger

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Hi David, I have several TR6 14W wiper motors, all working.  If your interested  PM me. Rich

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Looks good Roger, very similar to the TR6 set up. I guess  a metal 'U' as the 6 would do fixed with small 2BA size bolts rather the spot welds as the 6. Trying to keep it original though.

But may go this way if can't manage to convert a DR3A to 2 speed, not yet sure of where the connection of the resistor  is across  the field coil?  Rich

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  • 2 weeks later...

Question for Alan T.

In my quest to convert a DR3A to 2 speed, I have come across a DR3, I think ex Rover, but I'm not sure if  this can be utilised to make up a DR3 suitable for my TR4A.

The markings on the Wiper are: 75325F.  DR3 G118. Park with a right facing arrow. 12v 10 62. 073148E.

It had 5 wires plus a case earth where other  DR3A's I've seen have 3 wires plus case earth.   The park method is via a switch  arrangement inside the gearbox. 

It also is  a 120 drive wheel, so not suitable, I believe the TR4a requires a 150 drive wheel and gearbox, which I have. 

Appreciate any comments.

Thanks 

Rich

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Hi Rich,

 

the TR4A/4   requires a 120 degree wheel.  The TR6 uses a 115 degree wheel as they have different size wheel boxes

You do not have to have the auto park - turn it off when it gets there.

The single speed DR3A is also worth considering as the second speed on the DR3 is hopeless. 

 

Roger

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17 hours ago, rvwp said:

Question for Alan T.

In my quest to convert a DR3A to 2 speed, I have come across a DR3, I think ex Rover, but I'm not sure if  this can be utilised to make up a DR3 suitable for my TR4A.

The markings on the Wiper are: 75325F.  DR3 G118. Park with a right facing arrow. 12v 10 62. 073148E.

It had 5 wires plus a case earth where other  DR3A's I've seen have 3 wires plus case earth.   The park method is via a switch  arrangement inside the gearbox. 

It also is  a 120 drive wheel, so not suitable, I believe the TR4a requires a 150 drive wheel and gearbox, which I have. 

Appreciate any comments.

Thanks 

Rich

That amount of wires is Jaguar/Rover and other up market car fitment and they do the up and down park arangement. Also fitted to the VC works cars.

Stuart.

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75325 is a "reverse-parker" type from a Rover, P2 I think. These have the field-coil brought out separately.  This is so they can be made to run backwards when set to park.

The gear will be marked 120 but this is the sweep angle when running.  When set to park they run back by another 40 degrees, 160 degrees between parking position and extremity of sweep.

120 degree is almost too much for a TR so you will never keep the blades on the screen with that one.  Oh and that's a single speed, 6-wire on the two-speed models.

So put that on eBay for about £50.  While you are there search for 75568 which is the correct part-number for a TR4A two-speed.

 

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Thanks Alan,

Will move it on.  Bit confused by Roger's comment above  that says "the TR4A/4 requires  a 120 drive wheel"?  How can I bench test it to make sure it runs. Which wires would I connect 12Volts /earth to.  Is live, green? 

Thanks Rich

e-mail.  rvwp@yahoo.co.uk

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Hi Alan,

difficult to ascertain the colours, there are 5.

Blue/ green, 

blue,

green,

white/green and

green/red

Also the case earth

Thanks 

Rich

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So you are trying to bench test a reverse-parker.

You must pair up the connections to the brushes with the connections to the field-coil. The special switch normally does this pairing.

You will find a GREEN wire and BLUE wire that are connected together.  Say you ignore BLUE and use GREEN

Pair the GREEN with the WHITE and this is the 12V feed to one brush and one field-coil end.

The other brush is the RED wire. Pair this with the other end of the field-coil which is usually BROWN and this is the OV supply connection.

If you can't be sure of the colours take of the end-cap and see where they go.

 

 

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Thanks Alan for your help. The basic motor function works, so the assumption is that properly connected to the right switch the other functions will work. Have stripped it down, cleaned it and checked the brushes etc and all are good. On to e-bay next.

Where would I get the little contact spring clip use on the DR3's that you have to remove to release the arm.  Seem to have lost one? Also a pair of the carbon brush insets.

Thanks 

Rich

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