Schumacher BossCat Comp Rebuild

[dr_gn]

Ash_ said:

Fantastic talent you both have there, do you work well together or does a bit of tension/stress rear it's head?

Thanks, but it's books, trial and error, and advice form the Model Engineering forum that gets us through. I'd say the only talent is not giving up, or compromising.

There's no hassle at all with him, some frustration on my part when I've told him something that turns out to be not the best way of doing it. Then again, just admit it, see what he thinks and do it again. He helped with some steam engine beds I'm making, and if fact at one point noticed I'd made an error with an angled fixture plate - saved re-making some parts. I'm not a patient teacher, so I have to be careful because it's easy to make a fool of yourself by rushing or making assumptions....

He's always taking photos of his work to put on whatever social media he's on, and he's clearly proud of the results. He will default to online gaming all day long, but when he decides to do stuff like this, or his Warhammer models, it's 100% concentration. I just let him do what he wants to do at the time (which is why this rebuild is taking so long!).

[dr_gn]

Battery arrived:

[dr_gn]

New pair of spring retainers made tonight. One was missing, but now we’ve at least got an aluminium pair, and a plastic pair:

Edited by dr_gn on Thursday 1st July 21:56

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n3il123 said:

Lovely, I wish I had the skill and knowledge to make something like those.

Must admit it’s been great to work on this car, making bits and pieces with my son.

[dr_gn]

Made a new layshaft bush/spacer last night; old one was worn and the edges had become razor sharp. Probably caused by a seized bearing.

[dr_gn]

The original layshaft was a bit ropey, so we turned a new one:



Cross-drilled and made some drive pins out of an old twist drill:





All clicked together quite nicely:





Also straightened a few bent axles:



And test-fitted the chassis parts:



Assembled the gearbox, and fitted to the chassis:





…but something was amiss with the differential. It was solid both in normal and differential rotation when the compression bolt was tightened. So after some stripping we found a cracked washer holder, which must have allowed the central bosses to bind:



And despite filling any oversized screw holes with Epoxy, and re-drilling, some screws wouldn’t re-tighten. All in all a bit of a disappointing start. Still, the gearbox pulleys and belts all lined up and it turned very smoothly.

So now to source a new male diff washer carrier…

[dr_gn]

According to the Vintage Schumacher FB group, these things are very rare, so we’ve got a problem. Already spent more than the car’s worth, so hmmmm. Might try machining a pair.

[dr_gn]

Benni said:

Great thread, good job by both of you, would you adopt a 16 year old trapped in a 60s german body ?

If those special washers are that rare, maybe manufacture some more than needed and sell them for budget adjustment ?

Thanks Benni. No I think one teenager is enough!

We started machining the holders yesterday. The only issue are the tapered castellations on the output stubs. We tried marking them out using an original as a printing block, then razor-sawing the vertical bits and then snapping the stubs by working with a wood chisel (I know, it’s poor). The castellations really need wire eroding, or the whole thing casting, but that’s beyond our capabilities at home.

No way good enough to even think about selling, but I do believe we will end up with a pair of useable items which will at least get us running. Progress so far:









Thanks!

[dr_gn]

Hit a bit of a wall with this due to the broken diff parts, but I recently got a rotary table, and so these were the first bits we tried on it. Started by turning the spigots for the bearings and castellations:



Made two blanks:



Clocked up in the R/T:



Then milled the castellations with a 1.5mm end mill:





Took three angles to mill all the slots clean: 0, 22.5 and 45 degrees, with the cutter offset to half the diameter:





Finished:



Very nice fit on the output shafts and bearings:



Then made a split bush to hold the part to mill the other side:



Started by turning the basic shapes, then transferred to the mill for the lobed features:



Three flats, 120 degrees apart:



They are different side-to-side, spigot and socket:



With the hardened washers fitted:



And the assembly with bearings and output shafts:



And fitted to the ball retainer/pulley:





Assembled within the pulley:



Works fine, smooth as silk. So that’s the rear done, there’s another pair at the front, but we’ve salvaged a good pair of plastic ones for now.

[dr_gn]

Slow but sure progress on building it up:









The biggest issue has been dealing with oversized/stripped out holes in the plastic for the self tapping screws.

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Nightmare said:

Fantastic as always! I’m v jealous of your son lol

Also I now suspect you’re Steve from the Repair Shop

Not Steve, just someone who wastes many, many hours on the obviously uneconomical repair of anything repairable.

[dr_gn]

Promised Land said:

dr_gn said:

Not Steve, just someone who wastes many, many hours on the obviously uneconomical repair of anything repairable.

Do you come from an engineering background as the stuff you are both turning out is way beyond any DIY enthusiast?

Brilliant work though. A bit triggers broom but fascinating read.

Thanks very much! I do have an engineering background, but there are plenty of DIY type folks out there with garden shed workshops who turn out some very impressive stuff…I really think that lots of people who have no formal interest in engineering (or at least don’t admit it in public!) are very creative in an engineering type of way.

[dr_gn]

Just got around to this again after the garage got too cold to work in during winter. It’s not cold in there anymore…



Anyway, melted some brass inserts into the wishbones for the damper ball joints:









Also snapped an outer u/j yoke, but someone on the FB page kindly sent us a spare.

So now for the first time in a long time, it’s on its wheels:







Now to package the hardware into the chassis:



Also ordered some upper shock mounts from Schumacher. That should see it done.

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dom9 said:

Great work!!

Thanks! It’s been a good project.

First bench test run tonight - everything works fine so far, but it’s terrifying to watch - the tyres bulge out at full speed and look like they’re going to disintegrate. I’m glad we got new wheels and tyres - if one let go it would be pretty dangerous.

[dr_gn]

Got the electronics fitted - it just about all fits. Could do with tweaking the upper body a bit - maybe a heat gun might come in handy for some minor bending?









Tomorrow is the first test run fingers crossed…

[dr_gn]

First run was fine - pretty insane. A few people have commented over on the FB page about possibly a slipping clutch and gear mesh problems, but I think it seems ok. Not sure if the videos below will work.

We will have to get the body finished because the chassis soon fills with grass cuttings…

[dr_gn]

bucksmanuk said:

What a great build!

I went for an interview at Schumacher’s in ’91. I was amazed at the amount of testing and R&D they did.

It was when I saw the wind tunnel – I thought “Really? This is far more serious than I thought”

Thanks! I didn’t realise they went to that much trouble either. Maybe it was more for the sports car type bodies?

Made some minor mods today - cut-and-shut the ESC cover so that the fan housing mow fits within the body without distorting it:





And painted the undertray:

[dr_gn]

On the home straight now - attention’s turned to fettling the body…

[dr_gn]

So the Bosscat restoration is pretty much done. We used a colour scheme inspired by one of my favourite F1 car schemes, the Minardi M189. A few hard lessons learned about layering colours and pinstripe masking (lifted on all the concave radii), and the yellow overspray has ruined the pure white areas. Anyway, good enough for the garden. Still got the drivetrain whine despite tightening the clutch and diffs. I think it’s the large gear that’s a bit knackered - it’s quieter with the larger one. Goes like a stoat though. Son is happy with it.

[dr_gn]

n3il123 said:

Looks great!

I remember .. back in the day.... long time ago I used to go to a club which raced indoors on carpet, all the rich kids had these (apart from one who had a zxr) all properly lowered on foam etc. I was very jealous as all I had at the time was a steel chassis'd Mardave Meteor ... *sucked to be me!*

Got some work pals coming round next week, one to re-build his old Cobra, the other to build - I think - a re-release.