eagle bus reindexing splines on torsalastic springs

This is a video of reindexing the torsalastic spring adjustment arms on the splines of the spring tube ends to a factory new setting. It took me a month to do all the changes. I had some other issues that needed attention while the rear end and springs were removed. I am pleased with my results after 7300 miles of driving before posting this video. I am no videographer and tried my best at it with no experience. This is technical work that would only interest Eagle bus owners who want to attempt to lengthen the life of the torsalastic springs on their coach. Enjoy.

[@douglasengle2704]

Beautiful work! The battle ship gray was good choice for the corrosion protection color on the torsion spring assembly. Not black that makes it hard to inspect the area and not so bright as to draw undue attention.
Eagle buses have a reputation of rust and corrosion. This was common with European vehicles not having inner fenders in the 1960s to protect from road salt grime build up. GM, Prevost and MCI buses greatly use stainless steel in their main structure making them long term vehicles with attention to corrosion issues. They rust in places such as suspension components.
It is the build up of road grime especially with road salt that rots out road vehicles. Well washed out areas are seldom major corrosion issues. Some type of protective rubber or plastic inner fender flap that doesn't itself trap grime might protect the bus's sensitive areas from road thrown corrosive grime. It is especially bad with capillary action for European vehicles with a rubberized undercoating to separate and pull road salt brine in. That can leave no metal with it all permanently in a heavy salt brine turning into a powder.
Apparently it is not possible to get new Eagle torsion rubber spring assemblies and they do stress out and deteriorate the rubber torsion spring. If enough Eagle bus owners could go in on a deal it might be with a lot of effort from some Eagle bus enthusiast hopefully a mechanic engineer a run of new torsion rubber spring assemblies could be created with modern materials and fix any longtime known engineering issues. The torsion rubber of today should perform better and last much longer than that of the 1970s and before.
Anytime Bus Grease Monkey is working on an Eagle bus with torsion spring issues he changes it over to using air bag springs. It is not clear if the torsion springs can just be removed leaving the suspension pivot geometry intact. If the torsion spring assembly is part of the suspension geometry that would likely mean they are being left in place with an air bag spring adoption just boosting the failing torsion springs.
Rubber springs would be expected to have friction building up heat. As an energy storage device it would be a poor spring, but for a vehicle suspension a great deal of its desired characteristics are for dampening motion which a rubber spring if not over heated would be able to absorb an upward movement then rebound theoretically dampening the energy motion to not oscillate past returning the suspension's to original road height. It would likely do this better at micro movements than traditional hydraulic shock absorbers providing tighter control.
Bilstein gas pressure shocks greatly addressed micro dampening motion taking over the Porsche track day car market in 1980 from Koni shocks and stayed that way for at least the next two decades. Koni shocks held up and were consistent, but lacked the micro motion dampening the Bilstein gas pressure shocks clearly provided and the Bilstein shocks also stayed consistent with prolonged high motion and high heat build up of road racing like Koni shocks which other shocks did not.
Koni shock corporation covers the market for shock absorbers. I talked to a Koni engineer at a Koni trade show booth where he talked about how Koni outfitted Amtrak passenger train cars with Koni shocks.
An aspect I saw in a previous video on the Eagle bus torsion spring system was the bus would change the pretension on the springs to maintain the correct ride height for a varying passenger load automatically. There is nothing on the rear suspension I see that could be doing that. Possibly it was only on the front suspension.
A reason for using air bag springs is they allow a soft spring rate for good isolation and allow changing air pressure to compensate for a varying passenger load to maintain the correct ride height that would change greatly due to the soft spring rate if not compensated for largely changing vehicle weight. Simply using air springs does not give a soft spring rate.
What is done with heavy duty trucks is the use of stiff leaf springs that deflect little with increasing load that are also a suspension geometry component that changes its shape typically undesirable i.e. the typical school bus is built on a heavy duty truck frame.
An issue even with long durably shock absorbers for cars is they progressively wear for an at-specification life of 50k - 100k miles. That is a short life for travel bus or railroad passenger car component.
When I look at travel bus shocks they look way undersized for the energy they are turning into heat. I would expect them to overheat and provide under specification dampening after a few large suspension dips and rebounds making them prone to blowing. The reason there are three shocks per rear wheel on an off-road race truck is to dissipate heat over multiple areas produced by softly dampening large vertical movements and have the shock last a reasonable time.
Active suspensions were being developed in Formula one in the 1990s till a driver got the other drivers to go along and ban them. An active suspension would use computer controlled actuators in place of springs and dampeners where the computer would read the road and vehicle motions and actively adjust the actuators to follow it and maintain vehicle dynamics. This would not magically eliminate the need to keep unsprung mass low and the chassis stiff, but a well implemented active suspension should be able tip toe over the roughest terrain and keep the tires continuously engaged with the surface. Some aspect of that is done with active shock dampening where the dampening can be changed in thousands of a second by computer to control the vehicle.
Watching the seasons change in this video implies this was long thought out project. Thank you for sharing it. 🙂

[@davida7784]

Doing this was a big experiment by me. If anyone has any questions, I can check back from time to time and try to answer. I've been greatly pleased with the results of adjusting these springs.

[@silvereaglesessions2521]

Thanks for sharing this. I wish I had seen it before we started, but we’re getting ready to reinstall now and seeing the process will be extremely helpful.

[@davida7784]

Great for you. It will be two years in March 2024 and the springs are still holding.