Christmas 2004 Tech Article
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A Visit to the Chief-Overdrive
4 Speed Transmission Factory
By Alan Campbell

By phone, I purchased the new Chief-overdrive transmission from my Indian parts supplier and made special arrangements to take delivery where the transmission is made, Irongate Machine in Bellingham Washington. My overall goal was and is a durable and reliable power unit in my 1947 Indian Chief motorcycle. Overdrive slows the engine for cruising and theoretically adds considerably to engine durability and reliability. I went to the factory to see how the transmission is made, get some pictures and meet the design engineer, Frank Byford. PEng. My intention was to learn more about the transmission and write about what I found.

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Home of the Chief Overdrive transmission in Bellingham WA.
Not long ago, my 1947 Indian Chief wasn’t a collector’s bike like it is now with special insurance and the tendency to draw crowds. This was my first vehicle, a cool old motorcycle that cost little to buy, but worked well. I had fun with it. Lots of fun, and dependable transportation. Now, I wanted a new dependable engine and transmission so I could continue to ride my bike without concern for breakdowns, missed shifts or popping out of second while passing on a steep hill.  I planned a custom motor built of modern parts with modern machine tools. I decided to use the modern 4 speed transmission. 

This plan actually involved a leap of faith, financial risk and some adventure because this wasn’t like buying a new mass produced automobile or motorcycle. The reproduction engine and the Chief-overdrive transmission, both substantial new innovations for the Indian community, came to market as specialized machinery produced in limited quantities using modern technology. I arranged to have the engine put together by a third party custom builder and not the parts supplier because this seemed to be the standard procedure at the time. I picked out reproduction cases, flywheels, rods and cylinders from one parts supplier. I chose a separate custom engine builder for assembling my durable and reliable Indian engine. Complicated.

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Here is the story on Alan's Durable Reliable Indian Motorcycle.

Here is the original announcement of the first Overdrive transmissions in the April 2000 VI. Please note that contact details etc have changed since then. For more info, go to the Chief Overdrive website, or contact your local Indian dealer.

The Chief-overdrive transmission, in contrast would come turnkey from the factory and be sold by any one of a number of parts suppliers as a standard product just like a piston or valve. Not so complicated.

Irongate Machine in Bellingham Washington machines all the components for the Chief-overdrive transmission. This article describes my visit to the factory in the spring of 2003. I got much more than a fine motorcycle transmission out of the trip and found inspiration for a very satisfactory conclusion to my Indian Chief Motorcycle project.

On my way from Northern BC to pick up the transmission in Bellingham, just across the US Canada boarder from Vancouver BC, I slept on a boat in Vancouver harbor. Worth the trip by itself I think. In the morning, I stood on a big, vacant dock by a pay phone in the chill and dark. Some tugs worked nearby in the grey light and I could feel the crisp sound of their props transmitted through the water and into my bones. The air smelled of sea and life. I didn’t see another soul around. Mist rose off the water into grey early morning light and I sensed the promise of a coming fine day. 

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Chief Overdrive transmission. The only real outwardly visible clue that this isn't an original Chief trans is the slightly thicker base flange of the shifter tower. Case is interchangable with original cases, but everything else is new design.
Too early for many businesses, I phoned ahead to the factory anyway, hoping to beat the early morning traffic. A cheery, efficient female voice answered, full of sunshine. “Yes, of course we are open.” I hear “This is business bright and early, American style.” Perfect directions lead across the border at the Peace Arch through farm country to a tidy building in an industrial complex near Bellingham Washington. The farm equipment reminds me of my motorcycle and where I ride back home. But I’m in the heartland of aerospace industrial manufacturing.

Several athletic looking women run the open front office, dressed comfortably and unpretentiously, west coast style. They received me graciously, quietly aware that their directions were perfect. Frank Byford showed me to an office filled with engineering tools, specifically his computer and library.

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General layout of the gear cluster and components. Click to see the drawing full-size on the Chief Overdrive website.
The Chief-overdrive transmission owes its existence to Frank Byford. Several people contributed, but Frank designed the transmission product. A limited manufacturing run of units sold as the Hanlon 4 speed. Frank oversaw testing. He moved to Bellingham Washington and now oversees manufacturing at this location. To me, this transmission looks to be beautifully designed, well engineered and expertly manufactured.  For clarity, let us call this unit, manufactured in Bellingham, the Chief-overdrive 4 speed constant mesh transmission for Indian Motorcycles. 

I wanted to see the design software because one of the areas in my field of interest is the development of “smart” computer information systems. Buildings to molecules, just about anything can now be engineered with automated design technology. Here, the engineer conceives the big ideas, and the software computes furiously to work out ideal material and design details based on standard engineering decision rules embedded in the system. The profile shape of the gear tooth, the parameters of a beam or the structure of a molecule comes from the machine not a T square and drafting table. Best of all, the end product can be code that computerized machines use to produce very accurate and consistent parts. Frank designed some gears and sprockets for me right on the spot, and I felt at home, even though this particular system was new to me. The essential concept here is that the design software undoubtedly constitutes a very important element in the Chief-overdrive 4 speed constant transmission. 

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Cross section showing bearings and seals. Click to see the drawing full-size on the Chief Overdrive website.
Transmission Design Concept.
The original Indian of Springfield transmission served the design purpose quite well for over half a century. Some recent improvements and innovations from a variety of sources, Kiwi, Starklite and King Clutch for example, stopped my old transmission from leaking and made it easy to shift, compared to the original. The very best improvement was the King Clutch designed by Rob Olsen. The original transmission suits motorcycle riding on lonely roads and slower traffic in 1960’s Canada although it can be used on modern roads. The old transmissions shed bits of metal, require frequent oil changes and present the rider, even the experienced rider, with the potential of popping out of second gear. This adds adventure and risk to the ride. Furthermore, work on a 50 year old transmission is restoration art, more complicated and less predictable than acquiring a state of the art unit which incorporates current engineering, modern manufacturing and state of the art materials.
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Drive shafts for constant mesh gears.

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Gears on shaft.

The original Indian Motorcycle transmission is a crash box design. On a summer job, I drove a logging truck with a crash box transmission. That strong transmission, required strong arms to shift and artful work with clutch and throttle. It made a boy feel manly and fully involved with the machine to double declutch against the barking engine. The transmission popped out of gear with a “thunk” if the shift didn’t fully engage. This happened once with a full load on a long hill. Not good. My co-rider, who owned the truck and who had a heart condition, jumped. I felt terrible.

The original Indian transmission shifts by crashing first and second gears just like that old logging truck transmission. For the Indian, shifting requires little strength and more subtlety in the shifting. Sometimes Indian riders hear grinding, and worse yet, that “not good” popping out of gear “thunk” sound. Quite possibly, application of power causes the main shaft to bend just a little when the transmission is in second gear. If the sliding gear doesn’t rest at the apex of the bend, and this location may differ from bike to bike, then the sliding gear will naturally tend to slide along the shaft and out of engagement. Less than elegant. But there’s good news as well. The third gear engages with dogs instead of sliding and crashing gears. Third gear-“Klick!” I like that shift into third because it feels like I’m home, safe at last. 

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Shifter mechanism.
Frank Byford’s 4 speed constant mesh overdrive design builds conceptually on the use of dogs for shifting. In the Chief-overdrive, all sets of gears mesh constantly, so we have no crashing in or popping out of gear. Gear ratios change when dogs engage the selected set of constantly meshed gears. Frank engineered a tapered cone shape so the dogs and slots tend to pop into gear, not out. 

In the overall scheme of things, Frank Byford’s 4 speed constant mesh design may seem to be a small step for shifting transmission ratios,  but it’s a big step for Indian Motorcycle riding. Likely this design will eliminate dangerous partial shifts, popping out of gear, the copious shedding of metal bits and the need for 500 mile oil changes. Contemporary engineering and modern manufacturing ought to give us durability, reliability and ease of use. Overdrive cruising allows the rider to keep up with modest highway traffic while revving the motor at slower, motor saving country road RPMs.

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The cam moves two forks when shifting sets of dogs into and out of  their matching slots.
Assembly of the transmission.
Frank and I left the office and went to an assembly area.  We put together part of a transmission so I could see the assembly process. It wasn’t tricky or difficult. The 4 speed overdrive case uses a slightly different finish than a half century old transmission case, but I wouldn’t change the 4 speed constant mesh. It looks good. The transmission tower has similar lines to the original, but differs in minor details. These are design features, not oversights. I think it’s brilliant that Frank’s design fits into essentially the same box as the original transmission.

The inside 4 speed constant mesh parts differ from original in the sense that originals look rough except where surfaces meet. I’m not surprised bits of metal come spalling off and into the oil in the original transmission. The Irongate parts in contrast, as can be seen in the photographs, look like jewelry. I don’t think slivers of metal will be flaking off these parts

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Chief-overdrive clutch basket.
I’m guessing there may be twice as many parts in the 4 speed constant mesh unit as we would find in the original Indian of Springfield design. The 4th gear overdrive, constant mesh, dog to slot shifting and sophisticated drive bearings all bring additional parts. But the design builds on the minimalist Indian theme. It definitely doesn’t replace Indian concepts with a bunch of gee whiz experimental stuff. Actually, when one of these units does eventually require rebuilding, the procedure may be less complicated than with the original transmissions due to the design. 

This is what I came to find out. Did we have a fantastical innovation or another solid Indian Motorcycle part that would improve durability, reliability and safety? It looked to me as if the design succeeded quite well in moving forward with the clean, uncomplicated Indian design approach. With the Chief-overdrive unit, modern manufacture and design gives internal parts a precise and polished look not apparent in the original gears and other parts. It doesn’t seem likely that parts will wear out quickly or spall off metal into the oil. If spares are needed, it seems reasonable to me that parts would tend to be obtainable because they are made on computerized systems by an established machinery company in what looks like a straight forward uncomplicated production operation.

I’m an amateur mechanic and not qualified as a licensed mechanic or registered professional mechanical engineer. The evaluations here constitute an artistic interpretation only.  I’ve done my best to report accurately what I saw and experienced and to make interpretations free of any bias other than my passion for Indian Motorcycles.  I have no financial interest in Chief-overdrive, Irongate Machine or any other Indian enterprise. I paid the market price for my transmission. 
Manufacturing the transmission.
Frank and I walked from an assembly area out on to the shop floor. This place looked more like another big office than any machine shop I’d ever been in. It was well lighted and clean. Men worked at brightly colored machines and wore clean, tidy clothes instead of soiled coveralls. This differed from the greasy grey lathes, knee and arm milling machines and grinders at the machine shop in my town.  However, when I looked through protective windows, I saw spinning cutters shaping out familiar looking pieces of machinery like stuff I’d used in summer jobs on the drill rig or logging show. The Irongate crew were making custom contracted runs of a number of different pieces of equipment with widely ranging applications. The Chief-overdrive 4 speed constant mesh overdrive transmission is one of the manufacturing operations at a modern custom plant, and not a home made artisan project. 

I saw bins of parts ranging from cases to gears and shafts. Frank Byford explained that all machined parts are machined on site. The only outsourcing is for seals, bearings, bolts, retaining rings etc which are standard purchased parts. Castings are made to order by top of the line foundries with Chief-overdrive owned tooling. Heat treating is conducted by approved suppliers only. The machining complexity of some of the parts can only be accurately produced on a consistent basis by utilizing computerized machinery, where the critical features are made in one setup instead of multiple setups on different machines.

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Overdrive trans can take racing strains too. 
The Shop's LSR Chief
Frank and I assembled part of a transmission on one bench, and then torqued a 23 tooth sprocket on to the transmission that I had already purchased from my supplier. Again, I noticed a huge difference between the Chief-overdrive 4 speed constant mesh and the Springfield Indian crash box with regard to the fit and finish of parts. This is to be expected. Engineering and manufacturing has moved forward in the last century. 

Installing the transmission.
For my durable, reliable Indian Motorcycle project, Plan (A) had been to mate this transmission with a custom built engine right there on a bench in the Irongate shop, then plop the power unit into my bike and go for a ride. This would have made a great story with terrific pictures, and I think it would have been fun for the people who make the transmission. But we didn’t have a motor. Shucks. Plan (B), the transmission goes into the standard beautiful wood box all transmissions get shipped out in. When I picked that transmission up in my hands and rotated the shafts, which moved like silk, I determined that absolutely, I would put together an engine myself and get riding as soon as possible. I’d use my own engine as a spare when or if the independent custom built engine appeared. I didn’t have the latest custom cases or flywheels, but I had one case half, the original flywheels and rods, some new replacement wearing parts, some tools and eBay. Frank fastened down the unit, put in a nicely assembled instruction book, and screwed down the lid. I picked up the box, put it in on the front seat of my pickup truck, turned the key and headed north with determination to build a motor onto that transmission and be motorcycling in the next few months. 

I did put my engine together, got big help from John Bivens Indian Engineering when I needed a bail out with the bottom end, and did the rest pretty much on my own. Loved it! I didn’t hurry, because I only had an hour or so after dinner 4 nights a week and I was away quite a bit. But the process didn’t take too long either. I used the 4 speed overdrive transmission at the end of the season as planned, and loved it. As I write this, my bike with motor and transmission installed and tested wait next door for snow to melt and the next riding season to begin. 

To install the transmission to my new motor, I loosely attached the transmission unit to the engine. I then firmly fastened the primary case on to the engine, without a gasket. Next, I stepwise tightened the transmission up to the primary, and then firmed up the transmission to engine. I went slowly and wiggled things so that the fitting was free of stress and bent parts. I checked the alignment of engine and transmission sprockets, end movement and so on. Perfect! First try. What a thrill. Frank Byford’s transmission fit a John Bivens bottom end without need for shimming or adjusting. I doubt these two men ever met or talked, but they have quality in common.

I used the transmission a little at the end of the 2003 season, but with a fresh motor, I didn't pour the coal to it or do any fast highway cruising. However, the 2004 season brought one gorgeous warm day after another.  I rode just about every day. After about 3000 miles of back road driving, I went on a fairly long ride with another person who rode a new BMW. He had more power and more gears, but we rode quite comfortably together. The posted speed ranged from 90 to perhaps 110 kilometers per hour. In fact the traffic flow exceeded the posted limit, which, sadly, is the custom where I live. I think we operated at 65 to 70 mph most of the trip, and a little faster where necessary for proactive riding.  We stayed with or slightly ahead of the traffic flow even on the hills, so that when it came time for motor vehicles to pass, we did the passing. I used overdrive for all of the highway speed riding, and probably wouldn't have cruised at the same speed without it. The bike will operate satisfactorily at lower speeds when in overdrive, but this isn't the best use of the transmission. For slower riding, the sensation of the direct connect 1:1 gearing in 3rd gear is far preferable to my sense of a great motorcycle ride.

I barely knew the BMW rider before we started out. Once underway, we really hooked up with inside outside proactive riding. We had one of the usual adventures with a death wish driver and handled it with delightful teamwork finesse. We became the cause point for what happened on our part of the highway. And I think we got to understand one another a little better too. I love rides like this. The four speed overdrive helps it happen on an Indian Chief.

Most riding took me out on curving back roads with hills and winding turns. Once, a bull moose with massive antlers galloped along beside me. I wonder what was going on in the moosey brain to cause that behavior? The Chief was faster. Another time, I stopped in the middle of a herd of deer. They didn't spook. I had a bear encounter. And again, the Chief was faster. I didn't use the overdrive very much, because it wasn't needed for most of my riding. But when I needed it, the comfortable high speed cruising was there without any sense of over stressing the motor. I like the 4 speed most of all for it's solid behavior in the first three gears. In a sense, this completes the bike for modern use. The transmission is quiet. It shifts impeccably well. I use synthetic oil and change frequently. I don't find metal bits on the magnet. I use a King Clutch. I find the bike runs smoother with the primary chain tension just a little tighter than the tension I used with the old crash box transmission.  I find a zero slop shifting linkage to be essential. And the motor needs to develop full power and run smoothly in order to take advantage of this new overdrive transmission. I received a factory notice with instructions for tightening a set screw. Modern engineering and product support has its benefits. My bike feels up to regular use in the driving environment where I live. 

I gather from talking with Frank Byford that something like 50 Chief-overdrive 4 speed constant mesh overdrive transmissions have been delivered since I picked up my transmission. There is an R&D program to identify problems and create improvements and options. I saw a new run of transmission parts on a visit to the factory in December 2004, so these gear boxes, together with improvements and product support seems to be an ongoing proposition.

Not long ago, I discovered that an electronic ignition leads to much better starting and far smoother running than before. The Chief-overdrive 4 speed overdrive transmission gives riders another bonus for safer, more comfortable Indian Chief Motorcycle use. The new transmission gives us smooth dependable shifting which we didn't have before, and overdrive for highway cruising at comfortable motor RPMs. 

Using the Chief Overdrive 4 speed transmission in Norway - two bikes each with Chief Overdrives operated for 5000 miles of Norwegian roads.

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3 brothers Kristoffersen from Norway and their Chiefs! Torkel, left, with his Arctic Rat 1936 and Jan Emil, right, with his 1953'ish Blue Master are happy Overdrive owners (click blue links to read the VI stories on their Chiefs). Petter, in the middle with his 1948, doesn't have one yet!


From: Jan Emil Kristoffersen 
To: Alan Campbell ; 'Torkel Kristoffersen' 
Cc: Moen ; Jan Emil Kristoffersen ; Alan Campbell 
Sent: Friday, March 19, 2004 8:11 PM
Subject: Re: 4 speed O/D performance review

Hello Alan!

Just a short report back:
What is it like to kick the engine over? Just like it used to be

What is it like to shift into first on a cold morning ? Declutch... click......engage clutch... whisper off. 

What is it like to shift through the gears while riding? Very smooth, but still easy to find the gears. But you need a no-slop gear change linkage

Can you down shift for engine braking ? Yesssir! Better than ever!
Does it pop out of gear ? Not yet!

Is it noisy? No! Only a slight singing on top gear according to Torkel; I ride with a full face Schuberth Concept helmet and hear nothing.

Does it rob power? No

Do metal flakes show up in the oil? No, only a small amount of grayish mayonnaise on the magneto bottom plug. 

Do you like the looks of it in your bike?  It looks very much like the old job, nobody apart from concourse judges and originality nuts will tell. 


1. It probably extends the engine life between rebuilds many thousand kilometers, as you can dial in a suitable gear for (almost) any gradient/desired speed and still enjoy  a no grind smooth gentlemanly cruising. 

2. Pardon me for being panegyric in my praise of this gearbox, but the difference from the old 3-speeder - and I have tried some of those in the previous 34 years - is so immense that it creates a whole new driving experience. 

3. With such a gearbox the telescopic 80 c.i. Chief would have been competitive up until 1960 at least.

Jan Emil

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