BSA A 75 Rocket 3

The BSA Rocket Three and Triumph Trident Projects

This page will be documenting my Beezumph triple project bikes as I get a chance to add to it. In the meantime I’ll put up photos and scans of articles of other triples

Update as of 15 May 2004 – the triple stuff has all gone to a new home. I’ve realized that I’ve accumulated far too many project bikes and the triples were waaaaay down the work on during the next decade project list. If I should buy one in the future I’ll probably go with a nice runner instead of a severe basket case.

Update as of 16 March 2003 – Several weeks back I picked up a complete front end and rear end from a Suzuki GS500 twin. As you’ll recall, the R3 came without wheels/forks or much of anything else, and I couldn’t see putting on stock wheels on with 19 tires and inadequate drum brakes.

The problem is getting the chain to clear the tire. BSA/Triumph didn’t see any reason to move the chain farther from the centerline of the bike, and it appeared that if I converted to 520 chain by shaving .125 off the inside of the countershaft sprocket I’d end up with the inside of the sprocket just even with the outside edge of the 130 tire on the 3.5 x 17 rear wheel. Offset countershaft sprockets are available from Philip Pick for the five speed transmissions, but for right now the R3 is going to stay with the four speed box.

I put the engine back in the frame to try and look some more at the chain line, and noticed that all of the engine mounting spacers were on the primary side of the engine. The thinnest one is 7/16, so I realized that if I swapped the spacers over to the timing side I could move the engine over 7/16. That should give me plenty of room for the chain to clear the tire.

I also noticed that even with the spacers in place there were still air gaps that would be closed only by tightening the motor mounts and bending the frame. I’ll make custom-fitted spacers to avoid that problem. I will have to machine the sprocket carrier for the rear wheel to move the sprocket closer to the center line of the bike.

The GS500 swing arm is about 5 longer than the stock R3. but there is plenty of room at the front to shorten it and weld in a new pivot tube to mate up to the R3 frame. I’m considering running about 1 longer on the swing arm, as I may try steepening the rake a little. Stock is 28 degrees, and even the learner bike GS500 is about 25 degrees. The GS500 forks are 37mm damper rod units, and should be a bit sturdier than the stock 35mm BSA items.

The 60mm x 30mm x 2mm wall rectangular tubing in the GS swing arm should also be stiffer than the stock swing arm. The GS front wheel can be fitted with an additional disc – I haven’t gotten to the point yet of deciding what to do on that, and what calipers I’ll run. I may end up making new triple clamps with more offset as the GS500 clamps are pretty flat, and I don’t want to end up with too much trail, especially if I don’t adjust the rake on the R3 frame.

To make it easier to fiddle with the wheels/forks/swing arm I made a stand that attaches to the center stand brackets in the back, and then has the frame resting on the front loop of the stand. I put some UHMW-PE plugs in the ends of the feet so as not to mar the painted surface of my lift. I very carefully determined how far the front loop needed to be placed to make sure it cleared the side stand tab, and when I went to install it found I’d managed to put it exactly under the side stand tab!

I cut the connector tube and added a 2 long section of tubing. Even measuring twice and cutting once doesn’t always work. The loops are 1 x .049 wall steel tube that I bent with my bender.

The brackets that pick up the center stand are scraps of 1 x .065 square tubing, and the connector tube is more 1 round. I fillet-brazed the stand together.

Colin Bradley sent me this photo he took of a nice R3 racer – R3 racer Note the big drum brake! 78K

The R3 basket case arrives home 25 January 2003. The top end is in a box – it came home a couple of weeks ago. No bodywork other than the rear fender, no wheels, no suspension (rust on the rear damper shafts), no carbs.

Why, it’s practically a runner!

Cycle Guide magazine was published by Bob Braverman, and it was one of my favorites because they did a lot of interesting project bikes (often because Bob wanted to go racing on them). I’m fortunate in that I’ve not only got a lot of the magazines, but Bob’s son Mike Braverman has given me his permission to use whatever material I want from them.

In the April, May and July 1971 issues there was a series of articles called Lots of agony, and not much ecstasy documenting Bob’s building of a Rocket 3 powered Rickman, which he took to Bonneville and ran at Orange County Raceway. I’ve scanned the articles and offer them here for your entertainment. As always, I’ve tried to keep the file sizes small while still maintaining reasonable legibility.

Alistair Laurie’s 998cc Trident

I had a veglia recollection of an article on in an old BIKE magazine about a fellow who built a big Trident for sprints and land speed competition. A post to the forum not only jogged my memory that it was Alistair Laurie (from Dalbeattie, Dumfries, which I think may be in Scotland) who built and rode the bike, but also resulted in some photos of the bike that were taken by various people on the forum.

The article was from the August 1979 issue of BIKE, and was written by Dave Calderwood. Laurie’s bike had a custom crankshaft made from EN40 steel with a longer stroke of 80.5mm, as when combined with his own big-bore barrels the engine displaced 998cc. The crankshaft was nitrided and weighed in at 7.5 pounds less than the standard item (which is no lightweight).

The engine also had tuftrided EN24 steel connecting rods with Cosworth F1 bearing shells. 33mm Amal carbs, bigger valves and 1.625 exhaust headers. The bigger valves fouled each other so he had to reangle the guides in the head, and replace the valve seats. The crankcases had to be opened up for the bigger crankshaft, and then the rods were installed with the rod nuts tightened through the sump plate.

The two plate clutch uses his own sintered bronze driving plate.

A magneto was driven from the inlet camshaft via a timing belt at 2/3 engine speed. Laurie also built his own North-style frame, and was going to use a dustbin fairing for the LSR runs

I recognized the wheels on Laurie’s bike as being made by Eric Offenstadt, and since Tony Foale was the UK distributor for them I asked Tony if he remembered selling them to Laurie. Tony did, and he also told me: I certainly do remember selling them to him. He had magnesium wheels and was the only person that ever came back and asked me to machine them thinner to save weight.

He was a great craftsman, he made the alloy tank and seat unit himself. I think that he wanted to break 200 mph. I have a vague recollection that he might have done it with a dustbin fairing.

The bike ended up very light, even by my standards; he was fanatical about the weight of each piece.

Alistair Laurie’s 998cc Trident Partially assembled engined from the BIKE article 41K

Alistair Laurie’s 998cc Trident Clutch, crankshaft and on the starting line from the BIKE article 142K

Alistair Laurie’s 998cc Trident By Cab, at Douglas, IOM, in 1978 43K

Alistair Laurie’s 998cc Trident By Frank and Elizabeth Bateman, Douglas, IOM, 1978 – engine detail 34K

Alistair Laurie’s 998cc Trident By Frank and Elizabeth Bateman, Douglas, IOM, 1978 41K

Alistair Laurie’s 998cc Trident By Frank and Elizabeth Bateman, Douglas, IOM, 1978 – 3/4 close up. Very arty looking with lots of gleaming alloy and saturated colors 52K

Alistair Laurie’s 998cc Trident By Frank and Elizabeth Bateman, Douglas, IOM, 1978 – 3/4 close up but from a different angle 40K

Alistair Laurie’s 998cc Trident By Frank and Elizabeth Bateman. This may be from a few years later. The tank has obviously seen some difficult times, but the rest of the chassis seems to be in pretty good shape for having been crashed.

Does anyone have any details on what may have happened? 58K

Cab also sent along this photo of a customized Rocket 3 he took at the same time as the photo of Laurie’s bike. It looks like it may have Dresda bodywork – if anyone can identify it for sure I’ll post the information here. The wheels appear to be by CMA. Unkown Rocket 3 By Cab, at Douglas, IOM, in 1978 40K

Some photos I took

My lightened T150 crankshaft After lathe and preliminary milling machine work 11K

My lightened T150 crankshaft On the mill making angle cuts – closeup 23K

My lightened T150 crankshaft On the mill making angle cuts 23K

My lightened T150 crankshaft Welding rods stuck into all the oil galleries. That’s blue layout fluid on the journals – not blue rust (real rust is red as you can see elsewhere) 23K

My T150 mockup On the frame fixture with an EPM wheel and a swingarm that fell readily to hand 31K

Lightweight PM external dry clutch and belt drive conversion Cover and assembled primary drive 20K

Lightweight PM external dry clutch and belt drive conversion Clutch bits 30K

Lightweight PM external dry clutch and belt drive conversion Transmission cover, sprocket and gears 26K

T160 AMA Production racer This was one I shot at the Laguna Seca AMA National in 1975. 54K

Dyno Charts

These are from the December 1972 issue of Cycle magazine, which included a shootout of the current superbikes.

Dyno chart #1 65K

Dyno chart #2 The one with the T150 57K

Quarter mile times were:

H2 – 12.283@110.29

KZ900 – 12.386 @ 110.7

T150V – 12.718 x 106mph

Norton 750 – 12.896 @ 104.77

GT750 Ducati – 13.289 @ 101.12

HD-1000 – 13.393 @ 99.88

Honda CB750 – 13.497 @ 100.67

The Trident was third fastest (behind the Kawasakis) in the quarter, and also the third quickest. It was second worst in braking force (at .889G), had the third fastest (behind the Kawasakis) road course speed (.3 seconds ahead of the Norton), was fourth in pounds/bhp, third heaviest, and came out just ahead of the Norton in the overall points tally for third place (behind the Kawasakis).

Triumph Trident / Rocket 3 Three-into-one Exhausts

Here are some exhaust specifications that people have given me, and some that I calculated. I’ve included comments about performance where they were supplied:

Back to the home page © 1996-2005 Michael Moore, last update for this page 01 June 2005

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