Harrison gearbox parts

Etz fergie

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Hi. I have recently got a Harrison L5a. Apart from being very dirty it all appeared to be good with very little wear anywhere. Unfortunately on stripping down the Norton gearbox I now realise why it has seen little use. The centre splined shaft which holds a cluster of ten gears has stripped splines at one end, and matching damage to the gears. The shaft is also badly bent. My best guess is that this was caused by someone engaging the box with the machine running. In any case this damage means that neither the screwcutting or power feeds can be used, so the machine is very much manual only. The only good news is that apart from the shaft bushes nothing else is damaged. I have tried all sorts to try and source parts, or even a replacement gearbox but without success.
I am very much hoping someone will be prepared to help me out by making replacements for the shaft and three damaged gears which are 32, 30 and 28t.
Hopefully I will have attached some pictures of the damaged shaft, and of one of the intact gears.
The shaft is 7.730in overall. The smaller diameter end is 0.481 in diameter, the larger end 0.619. The splined portion is 4.604 in length and the outside diameter of the seven splines is 0.618, with a root diameter of 0.545. As best as I can measure them The top of each spline is 0.112 wide and The roots are 0.105.
The outside/root diameter of the gears are 32t 2.120/2.019, 30t 1.996/1.696 and 28t 1.869/1.540. Each gear is 0.633 thick.
The hole through the shaft is for a taper pin which holds a collar on the shaft to align the gears with others in the box. Endfloat is controlled by the fact that the bush at the larger end of the shaft projects from the casting and bears on the face of the 32t gear. I would obviously be able to forward the old shaft and associated collar and pin, together with an undamaged gear for patterns.
Any help would be much appreciated.
 

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Lo-Fi

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OK, let's see what we can do!
I'll go through the measurements tomorrow and see if I can figure out what gearing we're looking at. The photos aren't quite clear enough to make out the exact spline shape, but hopefully they turn out to be fairly simple.
 

Etz fergie

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Ian you are very kind. I realise I have had a bit of a senior moment with the measurements of the 32t gear. The root diameter should be 1.811. I haven't put up pics of the mating 16 t gear on the other shaft as at the moment I can't get it off. It is apparently secured with a taper pin but I can't pick the pin out from the surrounding metal to be able to drive it out. I will try some acid and see if that brings it up. I will try and get some better pics of the splines as well. Many thanks. Fergie
 

Lo-Fi

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Those spines are going to take some serious thought. Could we get some better pics of the profile of the splined shaft please?
 

Lo-Fi

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Perfect, thanks for that! They're 15DP gears, but... Some will have been generated with "profile shift" to suit the fixed distance between centres of the shafts, which wouldn't suit meshing distance of many of the ratios if they'd used standard profiles. Not an uncommon practice for many gear sets on common shafts and not the end of the world to figure out. Does mean that "off the shelf" gears are not an option.

The splines look as if they might be flat bottomed and cut in three passes? Great video using that method here:

I'm hoping that's the case anyway, or cutting them would be very, very hard using home shop tools!

My musings on approaching the project:

Gear teeth:

Calculate profiles for each gear, allowing for tooth profile shift. Cut using normal means with dividing head and cutters. I don't have any 15DP cutters, but they're easily obtained and Im set up to do this otherwise.

Spline shaft:

Assuming we're looking at a "three pass" method, this is achiveable the same as gear teeth. I'll have a chat with some helpful people about whether a commercial cutter might be available, but this is looking like a custom grind flycutter type of job.

Inside splines on the gears:

This is the most challenging part. There are two options: Make up a broach using this method:
, or index it in a shaper using a ground single point tool. Cutting the broach would be essentially the same as the spline shaft. I don't have a shaper, but it's probably possible using mill quill feed with the universal head dividing turned vertical. Be a lovely shaper project if anyone else wants to chime in and offer help, though! Not impossible it's the kind of thing that Abom79 would tackle as a viewer project. He loves shaper work, and it would make excellent (and unique) YouTube content. I've no idea what or if he charges, though!

I'd maybe go for some meehanite as material. Cuts really nice and plenty strong for gears. Bronze would work too, probably even engineering plastic! prototying in Delrin wouldn't be the worst idea for the gears in any case....

What machinging capeability have you got there, Fergie?
 

Etz fergie

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Very interesting videos. I'm afraid I have very little capability as yet. I have a Myford ML4 lathe which I got about ten years ago. I also have an Amadeal mill, however I haven't got a dividing head of rotary table. My background is Cars and bikes. Give me and old car or bike to restore and I'm a happy bunny. What we are talking about here is way out of my comfort zone. I bought the Harrison because I am due to retire next year and wanted to get some decent machinery so I can get more into this once I have the time. At the moment I am still very much a novice. For example my last project was to repair an old Kity planer, and I made new pulleys for it to convert from flat to poly v belt drive. Most of the work on the Myford is tuning bushes, spacers and such. As to the likely cost of this, I don't know if you have any idea, but the only other way I can see me getting this repaired would be to find someone who has a spare gearbox, that's going to be £250 ish I would think, but so far I haven't been able to find one for love nor money. So more than happy to pay a fair whack for it. I have contacted some firms locally but the response is typically that it's not worth their while to make 1 so they're not interested. There is a firm in Luton I use regularly who do metal spraying etc but they don't have the facilities to do the machining either. Not much help am I !
 

Etz fergie

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Ian
I was in conversation with a friend last night and he may have come up with a solution. The reason for the splined is to allow the gears to drive the shaft, and so you can slide them on one by one as the shaft goes into the case. His suggestion is that you could make a new plain round shaft, then bore out each gear to the of of a tube which would fit over the shaft. If each gear has a slight counterbore on each face then each could be tig welded to the tube in turn, the counterbore allowing a recess for the weld so each gear will still fit snugly to its neighbour. The complete assembly can be lowered into the case and the shaft passed through, the two being pinned together. Not perhaps the most elegant solution, but seems perfectly practical to me. That would only need the new gears to be made, but without the hassle of the internal splines. And I could make the new shaft.
This was inspired by a repair we did gears ago and I had forgotten about. A friends bike had broken down whilst on holiday. Some investigation showed that a gear had stripped its internal spline in the gearbox. Like here the only reason for the splined shaft was for assembly purposes. So we found a local welder who welded to gear to the shaft in situ. You would have had to cut through the shaft to ever get it out again, but he never did. He rode it like that for ages as he loved telling people the story.
 

Etz fergie

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Ian
reference my last I have managed to find a 32t gear with the same profile. It has a different centre with a keyway but for what I am going to do that really doesn't matter. The same guy also has a 16t of the same design. They are both Harrison old stock parts from a different part of the machine. The 30 and 28 only have some wear in the splines, the teeth are ok.
So looks like I won't even have to get gears made. I have some 13x16 mm cold drawn seamless high pressure pipe which I think would work well for the sleeve to mount the gears, so would Just need to make the shaft. I am sure if I have a rummage I have some 5/8 bar from an earlier job I did making a dog clutch for the Myford. Then over to my mate as he Tig welds for a living, and is much better at it than me !
Just didn't want to waste your time when I think his idea is a viable, and simple solution.
I hope you haven't spent to long on this and your help is really appreciated.
Hopefully you won't think me too cheeky to ask some advice about boring the centres of the gears. The odd number of splines, and odd number of teeth on some gears is a nuisance. I was thinking of simply boring into the face of an alloy bar in the lathe to create a suitable diameter as a mount, like a die holder. Starting with the smallest gear, and increasing the bore appropriately for each in turn. I think this would probably be the easiest way, but have not done this before so wonder if I am missing anything.
Thanks again for your help and advice
Fergie
 

Lo-Fi

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Ah, perfect! I'd assumed that the splines were something to do with functioning of the gearbox, not just assembly.

Yep, making an arbor to hold the gears for boring is the right way to do it.

However... your gears are odd diameters, being "profile shifted" 15DP gears. If the ones you've found from the other parts of the machine don't match those measurements, they're not going to mesh correctly. Measure very, very carefuly before proceeding.
 

Etz fergie

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Ian
This was the point my friend made and In a wood for the trees way I hadn't thought about.
The layout is that this shaft sits between the input and output shafts. The tumbler meshes with the input shaft and one of ten gears on this shaft. The output shaft has two gears which slide on splines and are controlled by levers on the front of the box so that one or other of them comes into mesh with either the same gear as the tumbler, or one of the other 9. In this way you have umpteen different relative speeds between the input and output.
The important thing being that once these ten gears are installed they can't move sideways along the shaft, the splines just ensure that when one gear is turning they all do, which his sleeve idea accomplishes. Fresh pair of eyes and all that.
I will check carefully to see that the new gears mesh correctly as you suggest.
Once again thanks for all your help and advice.
Fergie
 
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