Thanks for the splendid comments. So, welding is very well possible, but the
risk of warping is too great. I always considered the mating face between
the main casing and the rear extension as the weakest point, because of the
great shearing forces exerted on the lower of the 6 small screws, when
hitting something like a high curbstone. Especially whit an overdrive box,
the distance from this mating face to the front(engine) and rear mountings
is long. A friend, Ivan Matthys, has of pile of TR and saloon boxes : I will
beg him for another casing. Ivan was with me at the Nurburgring race
week-end 3 weeks ago : it was the 1st outing of my new car, the TR4A that I
bought from Bob Kramer. My TR3 racer was wrecked in may 2014 at Zandvoort,
hitting a concrete wall in the flying start. The TR3 overdrive dogbox was in
the TR4A for the Nurburgring event. After a few practise laps, the box
started vibrating and seconds later the noise was alarming. It turned out
that the layshaft was bent to 1350 at the front, the rear needle bearing was
not affected. The input shaft and the 3rd gear are loading the front of the
layshaft, so I suppose that the Zandvoort crash was the onset of the gearbox
failing, it was in 3rd gear and since Zandvoort the gearbox had not been
used, exept for a short ride on a public road.
I had a spare gear set with me for the overdrive dogbox and with the help of
Ivan, we emptied a good close ratio gear box of a Jo Willems racer and built
the box with my spare gearset, a lot of work, only to have overdrive (and
dog engaging) in the Saturday race. Some complications happened when we got
tired : the Jo Willems gearbox was a Stag box with needle thrust bearings
and to get at soms small parts in the damaged box, we had to cut the casing
to pieces, because it was impossible to drive out the bent layshaft. The
Saturday race was disappointing : I started at the rear and I could overtake
only a couple of cars and towards the end, my car got even slower, so I
moved to the pits. Lots of aluminium dust in the distributor cap pointed to
a ruined distributor bearing, causing erratic ignition. After replacing the
distributor, a short test on an empty parking proved that the power was back
to normal, so I was waiting with impatience for the 1 hour race on Sunday.
But Sunday was very foggy, at noon it was not better and in the end, all the
races were cancelled. Although I've not been able to test Bob Kramer's car
to the full, I was not disappointed. I've learned a lot : it's a very good
car, nice to look at and it will be fast in the next race season.
The Nurburgring week-end did have another pleasing side effect : Ivan
regained enthousiasm for racing : he raced a classic Mini and was building a
TR6 racer, but the work has slowed down to a point that he thought about
selling the car. I'm responsible for the engine and drive train and also the
suspension and brakes. The engine block and cylinderhead are ready and
almost all the parts for the drive train and suspension are there. The
engine has 76mm bores, with epuispaced cylinders made of steel tubes and
nikasil coated. I don't know anything about TR6 camshafts : any idea's
someone? The engine has a billet steel crankshaft and will stand 7500rpm or
more. If you see a white TR6 in front of the pack in some video's next year,
it should be Ivan's car, not Stephan Shamshula's. Dreaming...
Marcel
-----Oorspronkelijk bericht-----
Van: TR4 Tony [mailto:tr4.tony@virgin.net]
Verzonden: woensdag 22 oktober 2014 9:30
Aan: Kas Kastner
CC: Van Mulders Marcel; FOT
Onderwerp: Re: [Fot] Welding of a gearbox casing
Just to add to this I know that some of the guys here use the later TR6
bellhousing with the additional ribs vertically and horizontally, but in
addition (especially when using a dog gear set which exerts vertical
pressure which stretches the casing) they use straps to clamp the gearbox
together over the remote housing. I've avoided this by careful selection of
casings and a few bits of steel bracketry at critical points and stiffer
engine and gearbox mounts, all of which do a little but often as I can't use
a dog set due to regs.
A lot of other things have been tried, such as TIG welding, epoxy bonding
etc but the strap arrangement seems to be the better option at the moment.
As Kas says a little flex in the downstream mounting is essential.
Fundamentally the main gearbox casings are not strong laterally or
vertically so anything you can do to stop them stretching will give benefit.
The late CC TR6 casings seem to be the best, maybe also the Dolomite Sprint
then followed by the LD and KD series stag. The old alloy is now quite
brittle so once a fault develops it quickly turns into a major oil loss
which means rapid gearbox failure due to heat.
Also beware tapping the casing in a weak spot for an oil cooler take off.
Enough said.
Regards
Tony
Sent from my iPhone
> On 22 Oct 2014, at 05:42, Kas Kastner <kaskastner@gmail.com> wrote:
>
> The gearbox is probably unusable and welding will just make the chance
> of more expense very probable. I believe it is a matter of harmonics
> vibration. I found this to be true in the Early TR-4 cases where they
> cracked a the bellousing tot he gearbox . We had a terrible time with
> this. I did find one way to help the situation. I made two steel
> hangers out of 1/8" cold roll steel trap 1.5" wide and attached them
> on each side of the gearbox at the bell housing then up to each side
> of where the battery box is. I then mounted these straps hangers to
> small rubber mounts to help with the shock and to take soem of the
> weight.. This saved me many races until the factory finally
> understood my problem nd then added the big ribs down each side. I
> also added 1/2" thick aluminum ribs on the side of the gearbox. One
> case worked fine but another made it impossible to line up the shafts
> due to the case changing shape under heat. The hangers will work though.
>
> *Never be beaten by equipment.*
>
> On Tue, Oct 21, 2014 at 2:50 PM, Van Mulders Marcel <
> van.mulders.marcel@telenet.be> wrote:
>
>> In 2 years, I had 4 broken gearbox casing : maybe one of these can be
>> repaired : it has a crack where the bottom of the gear casing and the
>> rear wall are mating. Considering the weight of the engine and
>> gearbox, the stresses at that point must be very high : the 4
>> cylinder TR's have 2 mountings at the front of the engine and 1
>> mounting at the gearbox extension. A gearbox with overdrive has this
>> rear mounting at the very end of this extension : the shearing force
>> between casing and extension must be very high, one should think that
>> the rear wall of the casing should be pulled out all the time in
>> racing. Has someone tried welding a gearbox casing?
>> Marcel
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