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MG Midget and Sprite Technical - Wiper sweep

Looking for an idea for increasing the sweep on the wipers. I've heard that you can change the gearing.
The wiper motor is 2 speed but I can't find a suitable switch any ideas?
Thanks
Peter King

Hi Peter,
Check what your gearing is. Take the gearwheel cover off and the degrees will be stamped in the face of the large wheel. It's probably 110 degs. You can buy different sweep angles. I put a 120 Deg one in mine. I got from a scrapyard Austin 1100, years ago, but if you Google online you should come up with several suppliers as the wiper motor was used across multiple cars. It gives a better overall sweep and also eliminates the annoying swept area gap in the middle between the two wipers.

The switch has no impact on the angle that the wipers sweep through.
GuyW

I changed mine to 130 degree IIRC.

But when driving it recently I found myself leaning and ducking down to the left to see round the uncleared patch in the top RH corner. I want to do a full on Prop-style redesign and have them sweep the other way and maybe reposition them on the scuttle, so that they better clear that section.

Sorry, do carry on... :-)

Malc.
Malcolm

Malc, if modifying, you could always go for the American version. 😁

But think of the extra wind resistance! 😱
GuyW

Regarding a suitable switch, the MGB was fitted with 2-speed wipers quite early on. A switch from one of them should do the job. The toggle switch is BHA4786 and the rocker switch is BHA5110.
Mike Howlett

The early MGB with 2-speed wipers used a square-bodied motor. I think the way it's wired is quite different to the later round-bodied motor, so the switches may not be interchangeable.
Dave O'Neill 2

The early B with square motor only had the single speed. To get two speeds on mine I had to change both the switch and the motor.
Paul Walbran

Yes, it is indeed a round motor but the wiring - and switch - are a bit different.

More info here:-

http://www.mgb-stuff.org.uk/wipers.htm#speeds
Dave O'Neill 2

You can change the sweep by drilling and repositioning the pin on the gear wheel. This is often done by kitcar builders.

Jan T
J Targosz

Good oount Dave, wiring quite different, I had to change that too.
2 out of three 40 years later isnt too bad I hope!
Paul Walbran

Interesting Jan T, do you have a link at all?
Jeremy MkIII

Repositioning the crank pin on the gearwheel is effectively what the bought in conversion gears do. I like that as an alternative low cost solution though! With some careful measurement and basic maths one should be able to work out how to get the desired angle of sweep. 120 degrees works quite well on a two wiper spridget
GuyW

Guy I asked Jan as maths, either basic or advanced is an obscure foreign language (had to retake Elementary Arithmetic O level which says it all)!🙄
Jeremy MkIII

Jeremy, the actual stroke in degrees would, to me, be a complex thing to work out, depending on obscure things like the pitch and number of teeth on the gearwheels behind the dash. But there is a shortcut to all that! The crank arm under the cover of the wiper motor slides up and down, pushed by the pivot pin as the gear wheel rotates. The 'stroke' is twice the offset or radius of the pivot pin from the centre of the gearwheel.

So, if say the gearwheel is stamped 110 degrees and you want to increase that to around 120. That's roughly a 10% increase so the modification required is to relocate the pin further out by about 5% of the radius measured to the original pin position. 5% if measured and drilled accurately would give 121 degrees of sweep. But as long as it increased to roughly that sort amount, that would be acceptable. Anyway, exact accuracy is likely to be lost in worn components as well as as my poor skills at this sort of measurement.

Since I want to increase the sweep on the Frogeye wipers, I think I will have a go at this. What could possibly go wrong!
GuyW

Hi Jeremy,

I recall seeing a discussion on altering the wiper sweep on the Gentry Kit Car site. I am prety certain that if you remove the top cover of the wiper motor box and release the the arm that acts a connecting rod you would be able to move the the rack to its min and max positions using one of the wiper arms. This would give you the position needed for the pin on the gear wheel without any maths.

Jan T
J Targosz

Guy, Jan,

thanks for the further explanations. I think I need to try it to see how it all works rather than try to visualise it.
Good luck with the Sprite Guy 🤞!
Jeremy MkIII

Jan's method is even easier than my percentage based adjustment! I like that.
GuyW

The increased sweep between a 100 deg and 130 deg gear

HTH


Doug Plumb

150° anyone? Yours for £72.50 inc' postage. Bargain.

I'm not, never have been, circa 72 quids worth bothered, by a bit of unswept passenger vision. 😉

Drilling's the better part of valor. 😁

But standard's good enough for me.





anamnesis

150 degrees! That would keep half the bonnet clean as well! 😂

Passenger side clearance isn't the problem on my frog. It's the annoying missed bit down the middle that neither blade reaches. Probably as much to do with worn wheelboxes reducing the effective sweep.
GuyW

Yep, 150. Think there must be a mistake there. Lol.

Got me wondering now Guy. Does the frog sweep differently to the '66 sprite then? I've never noticed it (or at least been troubled by it), but I'll have to go and look now and see if there's a missed area on mine.
anamnesis

I think that if the wheelboxes, or maybe the cable'rack' is worn then the sweep is reduced as there is slack at the end of each stroke. Also, as the blades wouldn't then park as neatly down one is likely to move them round by a spline or two on the spindles to compensate leaving an even bigger gap in the middle! At least that's my diagnosis for the wee frog.
GuyW

I overhauled the Frog's rack and fitted NOS wheelboxes and rack. They park neatly but there is still a gap in the middle not helped by the rear view mirror. I guess its such a small screen some areas of vision are not that great. 8 inch blades are a challenge as well.
Bob Beaumont

This is why I've never thought about this, it's never troubled me. I've only got a pretty small unswept area. Mirror positioned to show small unswept area behind it.

Maybe I already have a 130° wheel then. As it happens I have to lift the lid anyway, because it doesn't always self park anymore for some reason.







anamnesis

Anam,
The parking is probably a fault of the parking switch on the round motors. There is a special plastic/nylon switch which plugs in -plunger may be gummed up or in my case partly melted !
Simply replaced mine when I refurbed and regreased the motor and rack wire.

R.
richard b

I've got the square wiper motor. Parking contact under the lid. I need to open it up, and I'm guessing I need to clean the contact.

Inside view from the link below that Dave gave earlier.

http://www.mgb-stuff.org.uk/ws.htm#1





anamnesis

It is a long time since I worked on a wiper system but I think you can dismantle the rack and turn it through 180 degs and similarly with wheel box gears. The rack works in a linear motion and the gears don't fully rotate so you can move them to an unworn section.

Jan T
J Targosz

This is the bit that upsets me! (Pic)

As for Moss pricing... wtf!!

Try here for any value from 90 degrees to 140 degrees for £25...

https://www.carbuilder.com/uk/search?q=wiper+gear

Malc.


Malcolm

Lol Malc. I thought you meant my door. 😁😁.

Anyway, 'snot that bad. 😄.

Good price on the 140°.




anamnesis

Car Builder Solutions does various geared wheels. Not sure if they suit the midget motor but just putting it out there.

https://www.carbuilder.com/uk/wiper-gears
P Peters

This thread was discussed between 10/11/2022 and 30/11/2022

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.