Cheap Telma retarders... if you have a bus with a long driveline...

[boogiethecat]

   Ebay  Item number: 160301392117   
The guy has 5, and the price can't be beat....

[Lin]

I assume that it would be too big for a MC5a.

[TomC]

If you have a V drive, or a tight and short driveline like the MC5, there just plainly isn't enough room for the Telma retarder.  Buses like the GMC PD4501, Prevost with Series 60, VanHool, newer MCI's have longer drivelines that will facilitate the Telma.  Otherwise, you'll have to stay with the tried and true Jake Brake.  Good Luck, TomC

[Sojourner]

The e-b a y # 160301392117 is a "drive-line" (double drive shafts) version of Telma retarder will only work in front and mid engine school bus or truck. You need at least 48 inch between transmission and pinion flange.

The only one work on MCI 6-7-8-9-12 and later model....are the "focal-mount" version of Telma retarder. These are mounting directly to the rear axle to eliminate one drive shaft.

Focal-Mount Retarder Click "Specification Sheets", "Focal (FN series)", "OC442046a FN 50-85 (F5750)" and stroll down to page 5.

FWIW

Sojourn for Christ, Gerald

[JohnEd]

Gerald,

You always come thru with really neat references and sites......this no exception.

The thing that always stuck in the back of my mind(not that far and clearly visable from the front) was that the loss of a U-Joint eliminated the Jake, Trans Retard, Exhaust stuff.  The u-joint became the "single point of failure" and I don't like that.  The Focul Mount Telma really clicked with me because you had to lose an axel to defeat its braking effect.  That and no maint, no heat load, no noise and No Bull.  Thanks for sharing that site.

John

[Sojourner]

About Telma system...at GM Tech Center, we use them of the Telma in-line version equips trailer to drag prototype vehicles for performace testing. IT WORKS! Unlimited braking also!

Thank you for the nice comment!

Sojourn for Christ, Gerald

[Kenny]

Interesting a driveshaft mounted retarder. Anyone use one of these on an MC9? Advantages/disadvantages over a jake brake? Cost/complexity over jake brake?

Kenny

[buswarrior]

No free lunch, the Telma uses lots of electric power, and makes all the same heat as anything else, only does it down against the differential, buried in the drive axle cavity, in the case of our T drive buses.

You can break many laws, but not physics.

Stopping or slowing always converts the energy of motion into heat, and the activating mechanisms require energy of some kind to operate.

Where you choose to deposit that heat is the choice a busnut has, not that one way makes less than the other.

Just clarifying for those less familiar and who may read the wrong thing into the thread.

happy coaching!
buswarrior

[boogiethecat]

Ah Buswarrior.  I choose to disagree, far, far from "no free lunch", having installed two Telma driveline units myself, one driveshaft style and one focal, on my two busses.  Definitely the BEST insurance money I've EVER spent.  And MUCH better performance and safety than any other retarder system.

Perhaps in your T drive busses the energy that the Telma converts may end up in a bad place, that I don't know.  But converting your downhill energy to hot air in a front or mid-engine bus like mine  instead of relying on Jakes or plain brakes is one of the best if not THE best idea anyone's come up with in years.  I have had on my bus: no aux. brakes; then an exhaust brake; then Jakes; and now the Telma and without ANY hesitation I would recommend a Telma to anyone who has a bus that one could be installed on, period.

They are quiet
They are super safe
Yes they draw upwards of 140 amps when running, but that's why you install a bigger alternator if you have to (I didn't and have had absolutely no problems)
Yes they make a lot of hot air, but for at least a few more years there's a lot of free cold air available to heat up. The difference is that they DO make your downhill energy into hot air, instead of toasting your brakes, overheating your transmission in the case of a tranny retarder, or making your engine work as a noisy compressor (poorly by comparison I might add).

An interesting aside from the downhill stuff, if wired into your brake pedal as can be done, the Telma also takes on 80% of your normal braking function as well, meaning double safety and very little brake wear.  I would actually be comfortable driving home with only the Telma should my brakes fail, as I've tried using the Telma manually in this mode to see what would happen (ie actuating it by hand instead of using the brake pedal as an experiment to see if I could safely drive with it alone if it ever became necessary). it works!

Anyway the point of my original post was not to argue the fine points of Telmas.. but instead to point out that for anyone with a driveline long enough, here's a Telma for you at a stupidly low price.  It's a big one, but there is really no "too big" with a Telma... if it slows you down too much you just don't turn on all 4 of it's windings all at once...

It's available, it's inexpensive, and if I had another few busses that'd take them i'd have never shared this ad !!!!!

Cheers
Boogie

[rv_safetyman]

Buswarrior, slight correction to your great post. 

Jake brakes do generate some heat, but it all goes into the same heat rejection system that the engine does (radiator and exhaust system) and it does so at a time when the engine is not putting out heat from generating HP.  Thus is it not any problem to get rid of the heat.

The two worst heat generators are the Thelma and a transmission retarder.  The Thelma rejects heat without affecting the other heat rejection systems, but can put a lot of heat into a localized area (like the rear end area). 

A retarder in my opinion is a very scary option.  It rejects it's energy into the transmission cooling system.  Used heavily, it will quickly overcome the capacity of the system and can create all sort of problems.  If you have a retarder, use it wisely and keep a VERY close eye on the transmission temperature gauge (you MUST have one if you use a retarder).

Jim

[TomC]

A comment on Telma retarders mounted directly to the rear differential.  Personally, I don't like it since it adds all the weight of the Telma to the rear axle possibly making the ride worse.  While Boogiethecat gets away with his mounted on the axle, he also has leaf spring suspension.  I know Telma will not mount the retarder on the rear axle with air suspension because of the heat issues (can cause air bag failure with the heat buildup).  The only other places to mount the Telma is directly to the transmission (can be an engineering nightmare) or to the carrier bearing-of which most buses driveline is too short to install one.
I agree with Gary that a Telma is the most powerful and quiet retarder available.  But most of us will not have the room for one.  Good Luck, TomC

[JohnEd]

I gather that the Telma will not work on an MCI as the driveshaft is too short....right?  Will it work on a Pre?  Don't ask why I want that info.


"and if I had another few busses that'd take them i'd have never shared this ad !!!!!"  There ya go agin Boogie, always think'n bout yourownself.


Thanks,

John

[HB of CJ]

Shame on you boogiethecat.  He he he.  Wish I still had my 10-wheeler Crown as the discovered, then shared E-bay retarders would be perfect for my application.  Jakes...30% to air, 70% to radiator heat rejection. Automatic tranny retarders...100% heat rejection into a marginal tranny cooling system....equals $disaster$ on long grades. $$$AUGH$$$.

Jakes are very cool and I love the sound, but for a Horizional Big Cam Cummins, they are becoming rather expensive to find and install.  Special oiling concerns.  Years ago we had a 48,000 lbs Fire Engine ladder truck that had the driveline retarder,  Had too.  Way overweight.  The retarder was like magic.  The service brakes never got hot. HB of CJ

[buswarrior]

Oh well...

What I meant to write... no matter which method you want to use, they all make heat, in relation to the "braking" they do, and that heat has to be considered, and managed, or not, depending on which you choose.

I was concerned that the earlier threads could lead a novice astray thinking the Telma does not have its own set of compromises, as does every choice for slowing down.

I'll throw a defence to the Allison trannies: A tranny that comes equipped with a retarder has a cooling system to deal with the heat. Whether the coach manufacturer/aftermarket hot rodder then puts in a sufficiently robust radiator, or the owner properly maintains the radiator/cooling system, or someone monkeys with the computer downshift settings, or the driver overheats it by letting it idle in a high gear while retarding on the long downhills, are separate issues.

happy coaching!
buswarrior

[HB of CJ]

Well said buswarrior.  Also ANY adequate cooling system can be overwhelmed by stupidity.  How about a 38000 lbs Type 1 Fire Engine coming down the Grapevine North bound at 75 mph in 6th gear with the Allision tranny retarder in the top setting (5 or 6?)....

...and the Firefighter never touching the service brakes and having that brand new $400,000 buck plus apparatus practically bursting into flames at the bottom of the Ridge route?  The reason he gave at the his "hearing" was "that was how he drove his car and he....

...didn't think the fire engine was any different".  Duh.  Anyway, about $25K to replace the Allision and related pieces.  Total toast.  If that engine had had a Telma type retarder, the firefighter still would have been stupid, but at least it would not have totaled the tranny and almost the fire engine.

Good engineering and common sence would suggest that if one plans on running his 38000 lbs Crown Super Coach 10-wheeler ultimate Bus Conversion down the Ridge Route at 80 mph because he can and he wants too, then one should consider where all that local heat is going to go.

Jakes are cool, but they are noisy, plus the little fact everything in the drivetrain is subjected to massive reverse torque loading.  Like already mentioned, what if something breaks?  AUUUGHHHHH!  Crowns have huge 16 x 12 brakes, but they aren't THAT GOOD!  Yikes!

But, where would all that massive heat go if one had the mother of all Telma type retarders?  I mean something would have to be glowing red.  Heat shielding to protect the brakes, hoses, lines, floor, tires, etc. comes to mind.  Yep, no free lunch.  Heat is heat.  Thanks.  HB of CJ