I need to repalce a mainspring in a 17 jewel Riverside model 1899. The main spring that is currently in the watch has a home made end brace so I would like to put the correct one in, but cannot go off the size of the existing one because it is probably wrong. When I look up the spring on my chart, I find the following info:Witdth 2.8,strenth .17, length 635, description: hole models 1899-1908 17-19 jewels
The other spring on the chart is the same in all dimensions except the strenght which is .18 and it's description is for Model 1899-1906. Which one should I use? Any help would be appreciated.

Scott

The Waltham Part number for Mainsprings in the 1899 and 1908 is #2227. Strengths for these range from Dennison 4, 5, 6, 6.5, and 7. (mm equivalents = .19, .18, .17, .16, and .15).

As for what to get... The latest Bestfit materials listing I have has only the Dennison Strength 4 (.19mm) and 5 (.18mm) available.

Bestfit part number for DS4 = JA-713
Bestfit part number for DS5 = JA-710

I would opt for the JA-710 in a 17 J Riverside.

Here's a big question though. You said that there is a home-made end brace. all of the 2227 varieties are simple hole end mainsprings. The hole end engages a hook inside the mainspring barrel. Is this hook intact on your mainspring barrel, or has it been modified by some other watchmaker? If it has, these mainsprings might no longer work in your watch.

Mike, thanks for the advice. Can you tell me why these two mainsprings with different strengths are listed for the same watch? How much of an affect can that small amount of strength make in the watch?

When I referred to the end brace, what I meant was that crude hole was punched and filed in it. The spring was over 30 inches long in the barrel. That is 5" too much. Fortunately the mainspring barrel was not altered by the previous owner. I backordered both springs at LaRose this afternoon to be sure, but would like to put the watch back to original if I can.

The model 1899/1908 came in many different grades. from 7J grade 610 on the low end to the 23J Vanguard at the top end. Different strengths of mainsprings would address the different needs along this quality spectrum.

In general, lower jeweled watches tended to utilize stronger mainsprings, since there was increasing loss of power transfer across the train to the escapement. This was caused by the friction of nonjewelled bushings of the pivots. Higher jewelled grades could utilize thinner mainsprings due to better transfer of power from the mainspring.

This rule is very general though since you can get into different balance weights and hairspring strengths that might also come into play when choosing a mainspring.

Waltham, though, kept it pretty simple. The various Illinois Bunn Special models are a little more confusing since they changed the barel diameter and mainspring needs often in the evolution of that grade.

The other part of your Q... Effects of different strength...

To strong of a mainspring can cause an over-rotation of the balance wheel, which could cause the roller jewel to strike the back side of the horn of the lever fork. To weak of a mainspring can cause under-rotation of the balance wheel, which can have an effect on timekeeping consistency.

However, these are extreems and you wouldn't see these ends of the spectrums attained by going up or down one denison strength.

Sorry for being so verbose. But when you talk mainsprings, there's a lot of ground that can be covered. We could go on further to discuss the differences in modern white-alloy mainsprings vs. the blue-steel ones that were available when these watches were made.

Thanks Mike. I'm fussy, so my biggest concern was how much of a problem going from .17 to .18 mm would be. Knowing that I can get away with either is very helpful. Thanks again.

Hi Mike
Following this thread on mainsprings, Could you tell me what the diffrences are between the White alloy springs, and the Blue steel springs. Is the time keeping quality of the tmepiece greatly affected when going from one type to the other.

Frank

Frank,

I'm not positive on the metalurgy behind them. But my understanding is that the white alloy springs are less brittle, more resilient and not as easy to "set" with time and use. Blued spring steel gets weaker with each wind and unwind.

As to the timekeeping effect of using either... I don't see much difference over using a new-old-stock blued steel vs a new white alloy. Both springs will do their job well. The white alloy spring should have a longer service life though. I have heard some say that the white alloy springs are "stronger" than a blued steel spring of equal size, but I have not seen any adverse effect caused by the added strength, if true.

I vary rarely use any new-old-stock blue steel mainsprings. White alloy ones are inexpensive and readily available.

Perhaps others can add to this.

Mike

Thanks for the reply. I will put that information in my notes. I always buy the white alloy ones myself. I would think that over the years,that the blue steel ones would loose some of their resiliency,even just sitting around, and not being taken out of the package. I don't know that for a fact,just my thoughts.If anyone else has any thoughts on it,would like to hear them.

Frank


Frank