Marcel,
I'm wishing you the best with the TR4A but the result of our exchange is that I
am now the owner of a white TR6 racer. I have a lot to learn on the engine
building and Weber carburetors but the car is the same underneath. This one
came with a dog gearbox and I was interested to see the comment about the dog
gears stretching the cases. Should be interesting.
Bob Kramer
rkramer3@austin.rr.com
---- Marcel Van Mulders <van.mulders.marcel@telenet.be> wrote:
> 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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