Bronze Idler Gears

Bronze Idler Gears in the Lister Types (Listeroids), Bronze Gear In Lister Types?

Update: I’ve added a link to a YouTube video, it is amazing how many people are cocksure they know what they’re talking about. I remember the call I got years ago.. “I ordered a steel idler, and I’ve had a train wreck in the gears, I’ve replaced the idler and the cam gear ,but still it doesn’t run.” My reply was to check the gear on the crank, this is an interference fit, and as you see, it’s mighty thin in the area between the bore and the root of the tooth. Expect it to crack, and spin on the crank… this is sometimes the result of placing the steel idler in an engine that runs a lot of hours.

Yes, with just a little thought, you can see the value of the sacrificial gear, so much easier to change the idler than the crank gear.  Of course, we can all turn our attention to the Mechanical Engineers who understood the value of a roll pin, or designing a coupler that was weaker that the crankshaft and sacrificed itself to protect the far more expensive crankshaft.

Sacrificial parts ARE part of the KISS design, building everything that fails stronger is dumb. Best you study modern gear trains, and note that the easiest gear to change is often designed to be sacrificial gear, it’s the KISS way, and the smart way.

As for the reasons for gear failures, they are many! Wrong material composition, improperly hobbed gears, poorly located position for crank, idler shaft, or cam resulting in really bad gear lash. When things are not quite right, and you can run a bronze idler, and get 6000 hours of running and all the while prevent the rapid shedding of ferrous materials that contaminate the bearing shells and bushings, you’ve found a solution to an immediate problem for people who may not have the luck, means, or skills to source the best parts and correctly fit them. I’m looking forward to the video about checking the gear to make sure it’s properly made, and showing us all how to set the gear lash between cam, idler, and crank..

So here’s the video, have fun watching

Public forums offer us a chance to share ideas, some good, some bad. One thing I’ve noticed…. some of the most outspoken know the least about the topic. Before one considers commenting on the merit of a bronze gear, he should know and understand that we have replaced failed stock gears in several engines that failed very early (30 hours or less).  We replaced them with bronze and saw a lot service after the change, one engine we had documented hours on ran 6000 hours on the bronze gear after experiencing a train wreck on the stock gears.

My focus is off grid power, but on the next ring out of the bulls eye are those who want reliable power for backup power in storms and more. Guam’s last big storm is only one testament to value engineering. Well before the commercial power grid was rebuilt, there was a massive pile of junk generators building in the local metal salvage yard. Yes, Off Gridders are ‘one percenters’, we are interested in reliable small power plant that can run for a few months 8 hours a day minimum, and the other 99 percent of the population wants a bargain. who in their right mind would invest in satisfying the needs of our tiny segment? Who among us would be willing to pay the price for a stationary engine designed to run for sixty years as many once did?

I’ve seen an advertisement placed in a popular publication in Great Britain “buy my STEEL idler gear and all your idler gear problems will be gone”. Such an advertisement suggests the vendor has only started to inventory all the reasons gears wear or fail as there are many sources of troubles….. to name a few:

  • Poorly machined cam and crank gears with irregular teeth or improper pitch.
  • Crank, idler, cam shaft center lines not in the proper place.

Fact is, a new an idler gear made of cast iron or steel won’t fix these things, and may cause an expensive train wreck inside your engine.  It’s a fact that some owners won’t have the skills or knowledge to fix the cracked gear on the crank that is often the result of a train wreck like I describe.

The use of a steel idler can be similar to putting in a 60 amp fuse where a 15 amp fuse should be, it’ll never blow, but all the wiring might melt.. Ahhh says the seller, “just like I told you, that fuse might last forever, you may never have to buy another fuse!” More experienced people know they want the cheapest and/or easiest to replace part to fail and save the others, exactly like the fuse.

The bronze idler is more expensive, but it takes a shape and then work hardens. It mitigates the shedding of ferrous materials that often end up in the soft bushing materials in an engine that promotes ‘rapid wear’ in critical journals like the crank pin and cam shaft bushings.

Anyone who would comment that bronze is too soft for a gear material doesn’t understand that engineers have used this material in gear trains that carry thousands of horsepower. Look at diesel locomotives, the engineers who finally built a long life drive system to the wheels used bronze gears. You can also find a lot of industrial gear reduction boxes with bronze gears, they didn’t spend all that money to spec the bronze just because it was pretty.

There are articles you can find about gears and materials compatibility, I don’t claim to understand it all, but if you run a steel billet cam in a performance motor, you need to change the oil pump gear to bronze or it’ll wear rapidly and fail. The steel and the stock gear are not compatible. there are also notes that the bronze gear may not get along with other materials.

To my knowledge, JKson was the first to supply a >real< bronze idler for the CS clones, and the Request came from us here in the States because we had customers running long hours off grid and seeing failures. Ashwamegh sent engines over here that experienced failures in the gear train in the first 100 hours, not all of them of course, but enough failures where we were needing to find a solution and we got zero help from Ashwamegh. We ended up sending every owner of an Ashwamegh a bronze idler at great expense, this was a custom run of idlers at first. Do I suggest there were failures in one or two brands only? The fact is, I’ve sold the bronze idlers to people who experienced failures in many different brands of Lister Clones. I’m not sure there is one brand that hasn’t gone through an idler. I can tell you there are individual engines in many brands that never experience a failure, but do they have the hours of running? I do know quality control is an issue. It’s not a typical problem in the Dursley built machines, if there is a history of failed gears in any numbers; it has not been brought to my attention.

Joel Koch (Oregon) financed the research of idler failures and commissioned a gear company with 80 years of experience to look into the problem and recommend a remedy. This was done at great expense to him an of course it was done to help his customers when Ashwamegh would only comment that it was the end user doing something wrong. Several gear materials were tried and the more expensive bronze proved again to be the best material to use. But of course it took a while to get someone to supply a quality bronze gear, and that ended up being Jagdip Shah of JKson.

We have two 12/2s here in America that ran over 14,000 documented hours on bronze gears, NOT that there aren’t more. Since India often recommends a rebuild at 3000-6000 hours, we figure the bronze gear is doing a reasonable job, it mitigates the problems, it does not fix an improperly located shaft.

I’d like to recognize JKson here and now for making the effort to produce a gear train we can live with, it is fairly easy to inspect the idler and see it is wearing or not. The smart owner will replace it BEFORE it breaks! Usually the end of the teeth on the idler will be sharpened like a knife just before the train wreck. If you are unlucky enough to spin and break (usually a crack) the crank pulley, you will be in for some work.

The value of the bronze gear is now well understood by many who personally run the Listeroids long hours. Those who make comments about the bronze being all wrong for the job may be drawing off information where the materials the bronze runs against are different than what we typically see in the Indian Lister clones.

About now, some will ask why the Dursley Factory in Great Britain didn’t use a bronze gear if it were so darned good? My answer is they were using materials that worked well, and the accuracy of locating the shaft centers was likely done with far more accuracy. Whatever they did, it was more than adequate!

For the better answer as to what was used in the originals, we should turn to Historian David Edgington who has been of service to enthusiasts around the world.

My advice: If you are using the Lister 6/1 clone for off grid power or running long hours, build a file folder for pictures of your engine, use an inexpensive digital camera with a macro setting to take a picture of the idler gear installed in the engine. The flash and the big door access allow you to take wonderful pictures. Note how flat and wide the end of each tooth is. Take pictures at each oil change and look for rapid wear, you will see the width of this flat grow more narrow with wear. Make sure you change the idler BEFORE the train wreck, this is one of the weak spots in the Lister clones and deserves your attention!

So there you have it, we believe we’ve proved the value of the bronze gear, just one more opinion placed onto the world wide WEB, so many opinions … some written by folks with no dirt under their nails. I wish to thank folks from around the world who share their experience from their failures to running lots of trouble free hours with great success.

You might like to check out a trip Mamad made to see engines of the past who were designed to run many years in hostile conditions.

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6 Responses to Bronze Idler Gears

  1. Well George, as you well know I only import engines from JKSon and insist on bronze idlers – the people down under are reaping the rewards of the research undertaken by Joel and others like yourself. It is also to the value of feedback from DIYers with their field testing. I’d like to also publicly reognise JKSon for being a manufacturer who listens to customers and takes steps to improve when they can. These engines are a low volume production line for their factory and they may not be perfect like Lister engines from Dursley – but at the end of the day it didn’t do Lister any good did it? – Lister are not producing the CS engines – so who is the winner? – At least DIYers who have a “listeroid” are getting access to the base engine as a starting point then they can make a difference. It gives people with basic skills an opportunity to own an engine they can maintain and operate and have fun with – and generate some power or pump water and learn the value of simple engineering and the KISS principle. I am finding less and less contaminants in these JKSon engines – having said that they are like a lucky dip the one you don’t precommission before you use it will be the one that is bad news. The bronze idlers always make me smile – they look alien in one of these engines – obviously Joel and others liek yourself had to convince the Indian manufacturers they had a problem – here is a solution and do something about it – at least JKSon listened and acted on it.
    I am as you well know passionate about these CS engines and their long term survival in the “land down under” and availability of spares parts for the long haul to keep that dream alive. I am sorry that political powers that be chose to ban CS “listeroids” from your market – I am sure you have much larger sources of pollution.
    I didn’t realise your EPA people in the US cared so much about the planet in any case with the amount of toxic chemicals, insecticides, pesticides, weapons they deem acceptable – then kill off a low volume engine like a CS. You’d know from your own life stories how dangerous some industrial process chemicals, even solvents are – the EPA doesnt seem to be telling the big money end of town to cease production of those products. I suspect politicians there are kust like ours and just want to be seen to be doing something. It is isn’t as though there are millions of these engines in the USA and most owners use them for fun or back up power rather than off grid.
    As a customer once told me he couldn’t afford an old steam engine so he bought a JKSon engine and now generates power off grid and it keep him out of trouble and in his toolshed :), listening to the “pooot pooot sound of the engine and telling tall tales – usually engineering tales to his mates over a cold beer or two.

    Power to you George for your vision and inspirational work on these CS engines – and helping us realise their potential value to help us in hard times. Thanks also to Joel Koch and John Ferguson and Tony Dovey and numerous others for not giving up on this family of engines when it would have been so easy to do so. As relatively late enthusiasts of the “listeroids” in Australia we are lucky to keep the dream alive. I guess we had so many Genuine Listers in our rural communities to keep us busy we didn’t need “listeroids” – until now.

    • George B. says:

      I was born in 1948, and like many of my generation, I had no idea what master pieces of engineering these old engines were. we all have admiration for the Lister CS as simple as it is, but there were othermengines designed to run continiously, and we allowed them all to be scraped! too bad..

  2. Joe Solair says:

    That’s a great video on idler gears you posted.

    no doubt.. if you want the idler gear to last a LONG time, put one in that’s harder and

    tougher than the other gears. you can save money on roll pins by using drill rod too.

  3. Ralph G. says:

    As usual, well put. Some people should look at worm gear gearboxes, large input unit loadings,sliding friction between gears, and nearly always the worm is steel and the gear is bronze. And this is the preferred build technique.

    • George B. says:


      When we look at the Dursley Effort, the idler gears were spec’d to use a certain material they called cast#20. (If I remember what David Edgington’s research revealed.)

      It’s a fact, India has not come close to providing consistent Quality Control, in the manufacture of Listeroid parts.

      In a perfect world, we’d have precise centerlines, and well made gears, we might never consider an expensive bronze gear here IF that were the case..

  4. Homealone777 says:

    George Sir; What’s you’re take on the Lovson 6/1 CS Lister clone? I’m still looking things over about which one to go with. Can you change the idler gear out to Bronze in one of those? If that’s what I find in Canada. OR, Is it the JKSon that the guy in Canada is offering?

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