Making wheels for 115 degree wiper-blade swept angle

[AlanT]

I've promised a few forumites to make wiper gears that sweep 115 degrees.

This means moving the crank-pin.

 

The standard 4/4A sweep is 120 degrees and this is really a bit too much.

So the TR6 switched to 115 degrees.

 

Some unwanted wheels arrived recently from the other side of the world for this job.

 

So I'll show here how this goes along. First job is to remove the existing crank-pins in such a way that they can be re-used. The first few I did with a pillar drill but this method is much better.

 

https://flic.kr/p/BWTySZ

 

 

[AlanT]

Some time ago I made this jig to hold the crank-pin while I weld it in place:

 

 

I made a few 120 wheels but there were two problems. The wheels actually swept 121.5 degrees and all the while I was worried lest a spark fused the pin into the jig.

 

So I decided to modify it by using an adjustable copper eccentric bushing to hold the pin:

 

 

 

An eccentricity of 0.01in gives an adjustment of +/- 2.5 degrees.

Now you see why I wound up making 121.5 degree wheels on the first attempt!

 

It proved hard to set the eccentric, using a micrometer as I had hoped, so I made a setting pin and setting rings for 115, 120 and 130 degrees:

 

 

 

This worked well and I now hope to make accurate wheels, which is just as well because I've about eight dismantled wheels to put back together!

Edited December 26, 2015 by AlanT

[Motorsport Mickey]

Good work Alan, nicely thought out fix.

 

Mick Richards

[AlanT]

Making the setting rings is actually an unusual turning job. Normally you want to control the overall diameter.

 

But here this does not matter much, its the "wall-thickness" that's critical.

 

Fortunately I have this sweet mike:

 

 

Here ithe ijig is set for 120 degrees and I have put the 115 setting ring on. That tiny gap corresponds to the difference required to set the sweep back by 5 degrees.

 

Edited December 26, 2015 by AlanT

[graeme]

Impressive engineering Alan, I look forward to seeing the results.

 

Cheers

 

Graeme

[AlanT]

Hi Graeme, finishing wheels is welding work and it ain't welding weather here at present.

So I'm on angle-drives. Batch of eight. These wil all get well shortly.

 

This jig is a bit rough really, but it is only a welding jig.

[AlanT]

Had a nice afternoon welding up the 115 degree wheels.

 

I much prefer to do this kind of work outside on a nice day.. Today I watched the rainfall Radar and planned carefully to get the work done in the few hours between belts of rain.

 

I now claim to be the first bloke ever to use Radar to repair a 50-year old car part.

 

I am in effect, welding material 1/2in thick, because I am hitting on the end of the crank-pin.

Using the maximum current available to me, to get penetration right into the pin.

 

Some photos to come on here shortly, of course.

Edited June 30, 2016 by AlanT

[AlanT]

The welding jig worked out OK. Doing it again I'd make three jigs one for each sweep angle.

 

This is the five 115 degree wheels from the first real batch. I also made 120's and 130's.

 

 

I have to make sure that the back is flat and there is no weld lurking around the base of the shaft. This might cause the plastic gear to split.

 

The acid etch just makes the circular welded area show up lighter just to the right of the shaft. See how close to the shaft it comes at this sweep-angle.

 

 

This version of the jig gave much better perpendicularity of the crank-pin than the first version. Better fit so that the pin cannot get out of line.

 

Edited July 4, 2016 by AlanT

[stillp]

Impressive. How are you welding them? TIG?

 

Pete

[graeme]

Looking good, Alan.

 

Cheers

 

Graeme

[AlanT]

TIG welding would be nice. Tidier and quicker. But no. Just an ordinary MIG.

 

The preparation is important. I make a hole almost as big as the foot of the pin.

I weld half of it so I can see the penetration into the pin. Then I turn round and come the other way.

 

I have to remove the clamp screw on the second pass. You don't want to weld this in!

 

The factory just spot welded these and I've had a few missing the pin. Sometimes people have brazed the pin back.

This sometimes holds. Rarely is it in the right place. Or vertical!

 

Remember the position is very critical. The difference between a 115 and a 120 is only 20-thou or 0.5 mm.

You have no chance without a jig.

 

Perhaps I'm brave enough to post a photo.

 

[RogerH]

Hi Alan,

whatever way you do it I know you will do a top job. How many people would weld half to make sure it was attached.

 

I'm not a good welder. If I did it I would have made the hole smaller and turned the end of the shaft down to fit into the hole - then silver solder.

However having not done it I do not know what pitfalls would have been in my path.

 

You take your time and do a proper job - well done.

 

Roger

[AlanT]

I don't get on with silver-solder. Like welding it takes practice.

 

You'd need a lot of heat and the whole jig would be hot and would soon get messed up.

If i did it the flux would run and the pin would solder into the bush in the jig.

 

I welded five wheels before the jig got a bit too hot to handle. The jig is pretty much unmarked and will easily make many batches of these.

 

Making sure the wheel does not get welded into the jig is a big consideration.

You will notice I have the ground lead on the wheel-shaft! And I start the weld on the wheel-plate.

 

If I made new pins I probably would stick them through the hole but I am reusing the pin that I took off.

 

There is ONLY ONE weld here. So it better be a good one!

 

I took two-hours to unpack the welder, set up the welding bench. Sort out the parts and what to do to them, make ten welds and put the welder away. So these are not taking very long to actually make the welds.

Edited July 5, 2016 by AlanT

[boxofbits]

Great work and well thought through.

 

I would assume those who desire these modified angles, would first have checked for loss of wiper angle via wear and tear.

 

Loose wheel boxes, worn racks, motor bushings, wheel box splines and wiper arm splines can also conTRibute to a considerable loss of wiper angle.

 

Haven't we all found that dreaded driver's side wiper arm lying on the bonnet in torrential rain due to excessive wear! Worth checking.

[AlanT]

You are dead right. You can tell how critical this all is from my post.

 

I am trying to position these pins +/- 1 thou because that's half a degree on the sweep angle.

 

Between that crank-pin and the blade-tip there is the big-end spigot, the ferrule on the wire-rack, the gear in the wheel-box and the shaft of the wheel-box. Any or all of these is a candidate for 5-10 thou wear.

 

The TR6 went to 115 degrees probably because they found out that 120 is actually a bit too much.

 

I'm doing this to get more 120 and 130 wheels, when I have 150's I don't need. These 115-wheels are just a spin-off.

 

When I make 120's I set the jig so as to aim at 118. I don't want to come out big.